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Journal of Strength and Conditioning Research 34(1):p e1-e245, January 2020. | DOI: 10.1519/JSC.0000000000003450
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Research Abstract Submission

Thursday, July 11, 2019, 8:30 am–8:45 am

Reciprocal Forearm Flexion-Extension Resistance Training Elicits Comparable Increases in Muscle Strength and Size With and Without Blood Flow Restriction

E. Hill,1 T. Housh, J. Keller,2 C. Smith, J. Anders,3 R. Schmidt, and G. Johnson4

1University of Nebraska Lincoln; 2University of Nebraska-Lincoln; 3University of Nebraska-Lincoln; and 4University of Nebraska-Lincoln

Purpose: Low-load blood flow restriction (BFR) training increases muscle strength and elicits muscle hypertrophy without the stress associated with high mechanical loads. The underlying mechanisms mediating muscle adaptation as a result of BFR training may be related to muscle swelling. To delineate the effects that muscle swelling may exhibit on muscle adaptation, the purpose of this investigation was to examine the effects of short-term resistance training with BFR (RT + BFR), resistance training without BFR (RT), and BFR without resistance training (BFR) on muscle strength, hypertrophy, and neuromuscular adaptions. Methods: Forty women (mean ± SD; 22 ± 3 years) volunteered to participate in this investigation and were randomly assigned to either the RT + BFR (n = 10), RT (n = 10), BFR (n = 10), or control (n = 10) group. Resistance training included 75 (1 × 30, 3 × 15) repetitions of reciprocal isokinetic forearm flexion-extension muscle actions performed at 30% of concentric peak torque relative to forearm flexion and forearm extension strength, respectively. Blood flow restriction was applied using a KAATSU training device and was applied at a pressure that corresponded to 40% of arterial occlusion. Training was performed 3 times per week for 4-weeks and all training and testing procedures were performed on a calibrated isokinetic dynamometer at a velocity of 120°·s−1. Isokinetic strength, surface electromyography (EMG) and mechanomyography (MMG), and muscle cross-sectional area via ultrasound were assessed after 2- and 4-weeks of training. Ultrasound-based assessments of muscle thickness, echo intensity, and muscle blood flow were used to quantify changes in muscle swelling and were measured immediately prior to, 0-, and 5-minutes after training during the 0-week, 2-weeks, and 4-weeks testing visits. Results: Muscle strength increased similarly for RT + BFR and RT after 2-weeks (13.1 and 13.4%, respectively) and 4-weeks (36.9 and 25.8%, respectively) that was associated with similar increases in muscle cross-sectional area after 2-weeks (11.3 and 12.4%, respectively) and 4-weeks (21.9 and 20.0%, respectively) of training. Although to a lesser magnitude than RT + BFR and RT, BFR alone increased muscle strength (8.6%), but did not elicit muscle hypertrophy. The changes in muscle strength for RT + BFR, RT, and BFR were associated with increases in MMG amplitude, MMG mean power frequency, and EMG mean power frequency, but no changes in EMG amplitude. The magnitude of muscle swelling was similar for RT + BFR and RT conditions at all time points, but increased to a lesser extent in BFR alone. There were no changes for the control group. Conclusion: These findings indicated that reciprocal forearm flexion-extension muscle actions elicited comparable increases in muscle strength and size with and without a BFR device. These similar adaptations as a result of RT + BFR and RT may be related to the magnitude of muscle swelling and/or motor unit firing rate (MMG mean power frequency). Interestingly, BFR alone elicited small, but significant increases in muscle strength. Practical Applications: These findings contribute to the growing body of evidence regarding the underlying mechanisms mediating muscle adaptation as a result of BFR and non-BFR training. In addition, coaches and practitioners can utilize low-load reciprocal resistance training to elicit positive adaptations to skeletal muscle. Future studies should examine BFR alone as a potential mechanism to augment muscle rehabilitation.

Thursday, July 11, 2019, 8:45 am–9:00 am

Constructing and Implementing a Confirmatory Factor Model Using Skill and Strength for NFL Combine Measures

K. Allen,1 C. Thomas, R. Herron,2 J. Cook, and G. Ryan3

1The University of Southern Mississippi; 2United States Sports Academy; and 3Georgia Southern University

The National Football League (NFL) annually invites a select-group of potential players to perform in a scouting combine. A major component of the combine is a battery of anthropometric measurements and performance-based assessments that include a 40-yd dash, 20-yd shuttle, vertical jump, broad jump, 225 lb bench-press repetitions, and 3-cone drill. However, it is less understood how these assessments relate to when/if the athlete is drafted to a team. Purpose: The purpose of this study was to investigate how combine results can be factorially grouped to best predict draft pick order using NFL combine data from 2013 to 2017. Methods: To investigate the constructs and structure of the combine results, an exploratory factor analysis (EFA) was conducted. This analysis used data from 2013 to 2015 with Quarterbacks and Kickers excluded. The EFA using a principal-axis factor extraction was conducted with the scree plot and Parallel analysis recommending a two-factor solution. For interpretation of the 2 factors, an oblique rotation was used, and the component loadings indicated 2 factors, Skill and Strength. A Confirmatory Factor Analysis (CFA) was done using the data from 2016 to 2017. After the CFA, an ordinal regression was run using the factor scores for Skill and Strength, to predict which round the player would be drafted in. Results: The EFA using a principal-axis factor extraction recommended a two-factor solution for the data. The CFA yielded the same two-factor model which fit the data, χ2(df = 17) = 184.253, Comparative Fit Index (CFI) = 0.959. The two-factor model confirmed that Skill and Strength were latent variables that could be determined from combine measures (see Figure 1). An ordinal regression using the factors to predict which round a player would be drafted in had good fit with the deviance goodness-of-fit test, χ2(4,191) = 2,215.327, p = 1.00 and the final model over the intercept-only model was χ2(2) = 16.206, p < 0.001. Concluding that a decrease in Skill was associated with a decrease in the odds of being drafted in Round 1, with an odds ratio of 0.417 (95% CI [0.274, 0.635], Wald χ2(1) = 16.553, p < 0.001). A decrease in Strength was associated with a decrease in the odds of being drafted in Round 1, with an odds ratio of 0.458 (95% CI [0.304, 0.689], Wald χ2(1) = 16.553, p < 0.001). Conclusion: The CFA using Strength and Skill was a valid approach to determine performance in the NFL Combine over using only traditional measures. Using the factor scores may allow for a more accurate prediction of draft. When Strength and Skill measures decrease, the less likely the player is to be drafted in the initial rounds, when compared to being not-drafted. Practical Applications: If use of factor scores and traditional NFL Combine measures can yield a better prediction of players draft pick, this could be useful for further preparation, assessment, and scouting for players prior to the draft, which could provide great insight for coaches and personnel managers.

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Figure 1.:
Standardized Regression Weights for the Accepted Model.

Thursday, July 11, 2019, 9:00 am–9:15 am

The Reliability of Pooled and Individualised Load-Velocity Profiles in the Power Clean and Back Squat

S. Thompson,1 H. Banyard,2 A. Ruddock,1 D. Rogerson,1 and A. Barnes1

1Sheffield Hallam University; and 2Swinburne University

Purpose: To investigate the reliability of pooled and individualised load-velocity profiles (LVP) in competitive Olympic Weightlifters using the power clean and back squat exercises. Methods: Ten competitive weightlifters (mean ± SD; age: 25.0 ± 5.6 years; body mass: 73.6 ± 13.9 kg; stature: 169.6 ± 6.6 cm) completed baseline one repetition maximum assessments in the free-weight power clean (PC) and back squat (BS) (1RM: 103.0 ± 22.8 kg; 154.4 ± 33.8 kg, respectively). Three LVPs consisting of incremental protocols (PC: 40–100% 1RM; BS: 30–100% 1RM) with mean (MV) and peak (PV) velocity, measured via a linear-position transducer were completed; each separated by 48–96 hours. Intraclass correlation coefficient (ICC), coefficient of variation (CV), standard error of the estimate (SEE), linear regression (r), repeated measures one-way ANOVA (p < 0.05) and effect sizes (d) were used to assess the reliability of the load-velocity relationship for pooled and individualised data. High reliability was defined a priori as: ICC >0.7; CV < 10%; d < 0.2. Results: MV and PV were highly reliable in PC across all sessions (ICC = 0.97–0.98) and relative loads (ICC = > 0.7; CV = < 10%). Strong ICCs for pooled data (0.98–0.99) and relative loads (>0.7) were evident for BS, but with large between-participants variation (MV: 8.72–27.04%; PV: 9.93–30.71%) (Figure 1). Stronger relationships were found for load and MV (BS: r = 0.95; SEE = 0.09 m·s−1; PC: r = 0.87; SEE = 0.08 m·s−1) than PV (BS: r = 0.81; SEE = 0.22 m·s−1; PC: r = 0.81; SEE = 0.16 m·s−1) in the pooled data. Individualised LVPs were stronger in MV (BS: r = 0.98–1.00; SEE = 0.02–0.06 m·s−1; PC: r = 0.87–0.99; SEE = 0.02–0.06 m·s−1) and PV (BS: r = 0.96–1.00; SEE = 0.03–0.11 m·s−1; PC: r = 0.85–1.00; SEE = 0.02–0.10 m·s−1) than the pooled LVPs (Figure 1). Within-participant variation for 95–100% 1RM was >10% in BS MV. 1RM data was not statistically significantly different between sessions (p > 0.05, d = ≤ 0.08). Conclusion: Performing LVPs across a range of submaximal loads met our criteria for high reliability in the PC, but not the BS (CV > 10%). Nevertheless, the criteria were met when utilising individualised LVPs in BS and PC, suggesting that load-velocity characteristics and neuromuscular recruitment differ across individuals, despite sample homogeneity. MV was more reliable than PV in both lifts, signifying greater stability across concentric muscle actions. Large within-participant variation was found at 95–100% 1RM in BS MV, potentially due to greater reliance on the mechanical and elastic properties of muscle at heavier loads. Practical Applications: LVPs can be used for assessing load-velocity relationships and practitioners can be confident that changes in LVPs are unlikely to be due to test-retest error. Individualised LVPs using MV should be utilised for PC and BS. When profiling BS, submaximal loads of up to 90% are recommended to reduce variability in the data.

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Figure 1.:
Load-Velocity relationship for mean velocity (m·s−1) and relative load (% of 1RM) in the back squat (A and C) and Power Clean (B and D) for the whole data set (A and B) and for one individual representative (C and D). 1RM, 1 repetition maximum; CV, Coefficient of Variation; LVP, Load-Velocity Profile; r, correlation coefficient; R 2, multivariate coefficient of determination; SEE, Standard Error of the Estimate.

Thursday, July 11, 2019, 9:15 am–9:30 am

Comparison of Individual and Group-Based Load-Velocity Profiling as a Means to Dictate Training Load Over a Six-Week Strength and Power Intervention

H. Dorrell, J. Moore, and T. Gee

University of Lincoln

Purpose: To explore the effects of 2 velocity-based loading methods over a six-week strength and power intervention in resistance trained males. Methods: Nineteen resistance trained males (mean ± SD; age: 23.6 ± 3.7 years; stature: 182.7 ± 5.1 cm; body mass: 92.2 ± 8.7 kg) were recruited. Following familiarisation, participants completed 2 custom back squat one repetition maximum protocols (1-RM; 150.7 ± 23.7 kg), with mean concentric velocity (MCV) monitored enabling load-velocity profiles to be created. Additionally, participants completed countermovement, static squat, and standing broad jump protocols (CMJ, SSJ, and SBJ, respectively). Participants were randomly assigned to individual (ILVP; n = 9) or group-based load-velocity profiling (GLVP; n = 10) groups, both featuring 2 training sessions per week for 6 weeks. For the ILVP group, load and repetitions were dictated based on individual data collected during the initial load-velocity profiles. In comparison, for the GLVP intervention, load and repetitions were dictated using a generalised group-based load-velocity profile, consisting of all participant data. For both groups, relative training loads and number of sets and repetitions were equated. Following the intervention, participants retested all baseline variables. Independent sample t-tests were completed to examine the pre-training inter-group, and post-training intra-group differences. A two-way mixed ANOVA, using one inter-factor (ILVP vs. GLVP) and one intra-factor (pre- vs. post-training), was conducted to examine the pre to post between group differences. Cohen's d effect sizes (ES) were also calculated. Results: No significant differences were present between groups at baseline. Training resulted in significant increases in 1-RM back squat for both groups (ILVP: 9.7%; GLVP: 7.2%), with no group by time interaction (F(1,17) = 3.97 p = 0.06). Significant increases in CMJ, SSJ, and SBJ performance were recorded for the ILVP group (6.6, 4.6, and 6.7%, respectively), and CMJ and SSJ only for the GLVP group (both 4.3%). Small to moderate ES were noted for both interventions across all variables (ILVP vs. GLVP; back squat: 0.66 vs. 0.43; CMJ: 0.32 vs. 0.21; SSJ: 0.25 vs. 0.21; SBJ: 0.32 vs. 0.19). Conclusion: The data presented demonstrates the potential impact of utilising a velocity-based loading approach on measures of maximal strength and power. Specifically, the results suggest that use of individualised velocity-based loading may offer a greater magnitude of change for some athletes when compared to a group-based approach. Practical Applications: Sufficient evidence is provided supporting the use of velocity-based loading interventions within a resistance trained population. While no interaction was witnessed between groups for the back squat or jump assessments, the ILVP group did amass greater percentage increases and larger effect sizes suggesting that utilising individual differences may potentiate greater physical adaptations. Such methods appear to provide the strength and conditioning professional with greater control over prescribing load, limiting the chances of unnecessary fatigue, while providing measurable performance increases.

Thursday, July 11, 2019, 9:30 am–9:45 am

Efficacy of an Acute Heavy Resistance Exercise Protocol to Study the Recovery Paradigm in Resistance Trained Males

L. Caldwell,1 E. Post,2 M. Beeler,2 J. Volek,2 C. Maresh,2 and W. Kraemer2

1The Ohio State University; and 2The Ohio State University

Adequate recovery from exercise stress is paramount for enhancing performance readiness and mitigating overtraining. Research investigating the effectiveness of new recovery modalities requires an exercise stress model of sufficient stimulus—providing a context in which to study the recovery paradigm. Identifying a reliable stress model is the first step in conducting recovery research. Purpose: To characterize the effects of an acute heavy resistance exercise protocol on biomarkers of physical and psychological stress occurring over a 48-hour recovery period. Methods: Eight resistance trained males (age: 23.3 ± 3.0 years; height: 176.8 ± 7.1 cm; weight: 87.6 ± 6.2 kg; strength to weight ratio: 1.8 ± 0.2) participated in this investigation. A baseline visit was utilized to determine 1-repetition maximum (1RM) and familiarize participants to the testing procedures. At least one week after the baseline visit, participants returned to the laboratory to complete a 6 × 10 back squat protocol at 80% 1 RM with 2-minute rest periods. Pain, soreness, mood state, energy, lower body power and circulating stress hormones were evaluated at 5 timepoints: before exercise (PRE), immediately post exercise (IP), 1-hour after exercise (+1HR), 24 hours after exercise (+24HR) and 48 hours after exercise (+48HR). Lower body power and jump height were measured during countermovement jumps on a force plate. Epinephrine (EPI) and norepinephrine (NE) were measured via plasma blood draw to evaluate stress signaling. The McGill Pain Questionnaire was used to evaluate intensity and quality of pain. A 100 mm visual analog scale (VAS) was used to assess overall and area specific soreness. The Profile of Mood States Questionnaire was used to assess frame of mind and VAS scale was used to evaluate energy and fatigue. Mean differences were assessed using a single factor repeated measures ANOVA with Bonferroni correction. Significant F tests were further investigated using pairwise post-hoc comparisons (p ≤ 0.05). Cohen's d was calculated to evaluate magnitude of change from baseline values. Results: The intense exercise stress resulted in increased fatigue (d; IP = 1.2, +1HR = 1.3) reduced jump height (d; IP = 1.3, +1HR = 1.15) compromised power (d; IP = 1.2, +1HR = 1.4) and increased circulating NE (d; IP = 4.6, +1HR = 1.1) at both IP and +1HR measurements. Mood was significantly reduced at all post exercise timepoints. Pain intensity and sensory characteristics were significantly elevated at all post exercise timepoints (d = 1.0–1.8), with IP significantly higher than +1HR, but not significantly different from +24 HR to +48 HR. Overall soreness was significantly elevated at all post exercise timepoints (d = 2.0–2.4). Quadriceps and hamstring soreness were elevated IP (d = 2.4) and +1HR (d = 2.0), while total number of soreness areas increased at +24 HR (d = 1.7) and +48 HR (d = 2.8). Conclusion: The large effect sizes demonstrated in this study highlight the intense stress placed on the body following a 6 × 10 back squat protocol at 80% 1 RM. Mood, pain, soreness, energy, jump height and power were negatively impacted at IP and +1HR, with mood disturbances and increased pain and soreness presenting through the +48 HR assessment. Practical Applications: The 6 × 10 back squat at 80% 1 RM provides a significant exercise stimulus, with homeostatic perturbations evident 48 hours after exercise. This protocol provides a valuable stress model that may be used in research investigations of the recovery paradigm.

Thursday, July 11, 2019, 9:45 am–10:00 am

High and Moderate Resistance Training Volumes Facilitate Similar Increases in Strength and Hypertrophy in Trained Women

L. Colenso-Semple,1 S. Bucker,2 B. Mueller,2 J. Longstrom,2 G. Rogers,2 E. Trexler,2 and B. Campbell2

1McMaster University; and 2University of South Florida

Purpose: To compare changes in lower-body muscular strength and hypertrophy in young women after 8 weeks of high or moderate volume resistance training. Methods: Thirty-seven resistance-trained women (mean ± SD: Age: 23 ± 4 years; Height: 63.7 ± 2.5 in; Weight: 134 ± 20 lbs) were assigned to a high-volume (HV) or moderate-volume (MV) experimental group. All participants trained on 3 non-consecutive days per week for 8 weeks with a total of 81 weekly sets (HV) or 36 weekly sets (MV) of lower-body exercises. Each session consisted of barbell squats (HV: 5 sets, MV: 2 sets), stiff-leg deadlifts (HV: 5 sets, MV: 2 sets), barbell hip thrusts (HV: 5 sets, MV: 2 sets), knee extension (HV: 4 sets, MV: 2 sets), lying leg curl (HV: 4 sets, MV: 2 sets), cable abduction (HV: 4 sets, MV: 2 sets), bench press or overhead press (HV: 2 sets, MV: 2 sets), and pulldown or cable row (HV: 2 sets, MV: 2 sets). Repetition range was specified as 6–8 (Day 1), 8–10 (Day 2), and 12–15 (Day 3). Loads were adjusted to ensure each set was terminated 2 repetitions from failure in the target range. All sessions were supervised by certified personal trainers. Assessments were conducted at baseline and 48–72 hours following the final training session. Muscle thickness of the anterior thigh, lateral thigh, posterior thigh, and gluteus maximus was measured with B-mode ultrasound. Strength was evaluated with a 6-repetition maximum (6RM) barbell back squat. Results: Strength and muscle size increased in both groups from pre-to-post intervention. A significant increase favoring the higher volume condition was observed for lateral thigh growth (+1.2 mm (MV) vs. +2.8 mm (HV), p = 0.046). There were no statistically significant differences between HV or MV in squat strength or hypertrophy of the anterior thigh, posterior thigh, or gluteus maximus. Overall, 6RM squat increased by ∼24% (32 lbs), muscle thickness increased ∼4% (2 mm) in the anterior thigh, ∼5% (2 mm) in the lateral thigh, ∼3% (1.9 mm) in the posterior thigh, and ∼1% (.8 mm) in the gluteus maximus. Conclusion: Lower body strength and muscle size increased similarly with 8 weeks of moderate- or high-volume training with all sets terminated 2 repetitions from failure. The higher volume protocol appeared slightly superior for hypertrophic adaptations of the lateral thigh. Practical Applications: A moderate-volume program of 12 sets performed 3 times per week provides a sufficient stimulus to increase squat strength and lower body muscle size. Training to failure is not required to facilitate strength or hypertrophic adaptations in resistance-trained women.

Thursday, July 11, 2019, 10:00 am–10:15 am

Monitoring of Body Composition and Physical Performance in a Division II Football Team Throughout a Competitive Season

M. Norford,1 M. Magee,2 J. Fox, S. Williams, J. Kollars,3 A. McCracken,2 B. Comstock, J. Andreacci, and K. Beyer2

1Applied Body Science; 2Bloomsburg University; and 3Bloomsburg University of Pennsylvania

American football is a sport requiring repeated high-intensity efforts that result in on-field collisions. These on-field demands are met by each position with training to achieve a specific physical skill set and body composition. However, in-season competitions may affect physical performance and body composition, specifically in programs with limited resources. Purpose: To assess changes in body composition and physical performance variables in a Division II football team during a competitive season. Methods: Sixty-five football players were recruited for this project. Subjects reported for 2 separate visits, the day before training camp (PRE) and the week after the last game (POST). During these visits, subjects were assessed for body mass via digital scale and percent body fat (%BF) via a 3-site skinfold. After, subjects were required to perform a vertical jump test via a vertec to assess jump height. Vertical jump height was then used to calculate vertical jump velocity. Vertical jump momentum was calculated as the product of body mass and vertical jump velocity. All players were categorized according to playing position into Perimeter Skill (defensive back, wide receiver), Interior Skill (linebacker, running back, fullback, tight end) and Line (defensive line, offensive line); all other positions were excluded due to insufficient sample. Results: Body mass had no time×position interaction (p = 0.281) or main effect of time (p = 0.726). Similarly, %BF had no time × position interaction (p = 0.117), but there was a significant main effect of time (p = 0.033). There was a significant decrease in %BF from PRE (17.4 ± 7.6%) to POST (16.4 ± 8.4%). Furthermore, no time × position interactions were noted for vertical jump height (p = 0.232) or momentum (p = 0.232), but there was a main effect of time for both (p < 0.001). Vertical jump height and momentum decreased from PRE (72.5 ± 12.0 cm and 380.3 ± 61.3 kg·m/s) to POST (66.5 ± 9.4 cm and 363.7 ± 60.8 kg·m/s). Conclusion: The findings of the study revealed that body mass was maintained throughout the season, with a concurrent decrease in %BF. In terms of performance, both vertical jump height and momentum decreased during the season. However, no positional differences were observed in the changes during the season for any variables. Practical Applications: This study's findings could be useful for coaches at Division II schools whose teams may experience similar in-season changes, possibly due to limited resources. Linear momentum may be a useful metric for American football because it is affected by the changes in both mass and velocity.

Thursday, July 11, 2019, 10:15 am–10:30 am

The Effects of a Multi-ingredient Pre-workout Supplement on Repeated Sprint Ability and Perceived Exertion

M. Magee,1 M. Norford,2 S. Williams, J. Fox, R. Inaba,3 J. Andreacci, B. Comstock, and K. Beyer1

1Bloomsburg University; 2Applied Body Science; and 3Cenegenics

Purpose: To assess the ability of a single dose of a multi-ingredient pre-workout supplement (MIPS) to elicit desirable responses on repeated sprint ability and rating of perceived exertion (RPE). Methods: Twenty women and 18 men were recruited to participate in a randomized, double-blind, placebo-controlled, crossover study. All participants were tested within the same week separated by 48 hours and were provided either the placebo (PLA) or the MIPS on each day. As per the manufacturer's instructions, the participants waited 25 minutes to begin the tests, following consumption of the drink. Participants completed a short warm-up which consisted of 2 minutes of cycling at 50 RPMs against a light resistance, followed by 3, 10-second sprints, to determine the max RPMs. After the warm-up, participants completed the repeated sprint test, which consisted of 10, 6-second sprints, with 45 seconds of active rest in between each sprint. For each sprint, a resistance of 7.5% of the participant's body mass was applied at 90% of their max RPM. Immediately after each sprint, differentiated peripheral RPE for the legs was recorded, as well as peak heart rate. Peak power and work were measured using the Monark Anaerobic Test Software. Peak power, work, heart rate and RPE were analyzed using a 2 × 10 (trial'sprint) repeated measures ANOVA, with post hoc paired t-tests comparing trials at each sprint. Level of significance was set a priori to p£0.05. Results: A trend in trial×sprint interaction (p = 0.068) was observed for peak power. There was significantly lower peak power during PLA when compared to MIPS at sprints 4 (p = 0.013, 651.2 ± 162.1 W vs 675.9 ± 169.0 W), 5 (p = 0.001, 615.2 ± 163.0 W vs 655.1 ± 176.9 W), 6 (p = 0.010, 598.5 ± 159.6 W vs 635.3 ± 166.3 W), and 8 (p = 0.011, 574.3 ± 155.8 W vs 613.7 ± 156.7 W), while there was a trend at sprints 7 (p = 0.065, 576.8 ± 159.5 W vs 614.3 ± 168.5 W) and 9 (p = 0.068, 575.4 ± 150.5 W vs 603.3 ± 156.1 W). A trend in trial × sprint interaction (p = 0.092) was observed for leg RPE. PLA had significantly greater leg RPE than MIPS at sprints 1 (p = 0.005, 3.4 ± 1.9 vs 2.8 ± 1.9), 2 (p < 0.001, 4.5 ± 2 vs 3.7 ± 1.9), 3 (p < 0.001, 5.5 ± 1.9 vs 4.7 ± 2), 4 (p = 0.010, 6.3 ± 1.9 vs 5.6 ± 2), 5 (p = 0.038, 6.8 ± 1.8 vs 6.4 ± 2), 6 (p = 0.033, 7.5 ± 1.6 vs 7 ± 1.8), and 8 (p = 0.049, 8.4 ± 1.4 vs 8.1 ± 1.5), with a trend noted at sprint 7 (p = 0.068, 7.8 ± 1.6 vs 7.5 ± 1.6). There was no significant trial×sprint interactions in work (p = 0.591), or heart rate (p = 0.607). Conclusion: This MIPS elicited favorable trends in power and RPE, despite no changes in work or heart rate. This MIPS may be able to increase peak power and reduced RPE during repeated sprints. These findings may be due to the caffeine within the MIPS, but future research should investigate further. Practical Applications: This MIPS may be an option for individuals looking to improve repeated sprint ability in a single dose. These acute benefits may ultimately result in greater adaptations to sprint interval training.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Predicting Ball Exit Velocity With an Inertial Measurement Unit in Collegiate Baseball Players

R. Eusufzai and C. Bailey

University of North Texas

Inertial measurement units (IMU) are increasing in popularity in research and in practice as a method of acquiring kinematic data, likely due to their minimal spatial constraints. This technology has been applied to several sports, including baseball, but their utility for performance monitoring and identification of key performance indicators (KPI) needs to be evaluated. Purpose: The purpose of this study was to evaluate the association between batted ball exit velocity (BEV) and kinematic performance variables assessed with an IMU. Methods: 13 collegiate baseball players (NCAA DIII) volunteered for this study (82.2 ± 10.9 kg, 178.3 ± 5.5 cm, 19.9 ± 1.3 years). After a total body dynamic warm-up and 10 practice swings (5 dry swings, 5 hitting off of a batting tee), 3 maximal effort swings were completed. During each maximal effort trials, athletes used a standardized bat to hit a ball off of a batting tee at a self-selected height. Kinematic swing performance data were collected via an IMU collecting data at 1,000 Hz. Variables included bat speed at impact (BSI), hand speed max (HSM), time to impact (TTI), bat vertical angle (BVA), and attack angle (AA). BEV was simultaneously collected a with radar gun positioned directly behind the batter. Association between IMU derived variables and BEV were evaluated via bivariate Pearson's product moment correlations. Results: BSI was the only variable shown to produce a practically significant relationship with BEV (r = 0.53, p = 0.06) but statistical significance was not achieved at the p ≤ 0.05 level. All results can be seen in Figure 1. Conclusion: While, the small sample size associated with this study likely decreased the chances of achieving statistical significance for many of the variables, only BSI was predictive of BEV from a practical standpoint. BEV and all the IMU variables are likely still important and should continue to be monitored, but further research is necessary to evaluate their importance to performance. Practical Applications: Based on the findings of this study, BSI may be moderately predictive of BEV. It is important to note that the current investigation only looked at BEV as a performance measure and there are many other KPIs associated with hitting that should be evaluated in the future. Furthermore, changes in IMU variables in response to different training volumes and associate fatigue may be of value.

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Figure 1.:
Plot depicting the correlation matrix, data distributions and scatter plots of each relationship. BEV = ball exit velocity, BSI = bat speed at impact, HSM = hand speed max, TTI = time to impact, BVA = bat vertical angle, and AA = attack angle. Statistical significance is indicated in the following ways: ** = p < 0.01, * = p < 0.05, * = p < 0.1.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Varying Shoulder Angle Increases Muscle Activation of the Biceps Brachii Without Impacting Volume Load Within a Training Session

J. Pearson,1 C. Barakat,2 E. De Souza, J. O'Sullivan, M. Alvarez,2 J. Rauch, D. Aube,2 and R. Barroso3

1The University of Tampa; 2University of Tampa; and 3University of Campinas

Introduction: Manipulating resistance training (RT) variables has been suggested as a means to optimize muscular adaptations. For instance, training volume and muscle activation are 2 variables that quantify the demands placed on the muscle within a session. However, there is a paucity of data on how these elements are influenced by varying joint angles within a training session. Purpose: Therefore, the aim of this study was to examine how altering the shoulder angle (glenohumeral joint [GH]) affects volume load and muscle activation of the biceps brachii within a training session. Methods: Eleven resistance trained individuals (5 males, 6 females, age: 21 years ± 1.47, height: 166.8 cm ± 7.1, body mass: 66.6 kg ± 10.4, RT experience: 4.7 years ± 1.91) volunteered for this study. Subjects performed 3 familiarization sessions prior to the experimental sessions. Baseline 10 repetition-maximum (RM) elbow flexion values were recorded during the familiarization sessions in 3 different GH joint angles (−30°, 0°, 90°). This 10RM load was used for the first working set of each experimental session and the load was adjusted during subsequent sets. Forty-eight hours after the familiarization sessions, subjects underwent 2 experimental conditions with a one-week washout period between conditions, control (CON) and varying GH joint angle (VAR), in a randomized, cross-over design. Before any experimental session, surface electromyography (EMG) was applied to the mid-belly of the biceps brachii. In order to normalize the EMG data, a maximum voluntary isometric contraction (MVIC) was performed at each shoulder position before starting the experimental conditions working sets. During the MVIC, the root mean square (RMS) of the EMG signal was calculated in 500ms windows, and the highest value was used for normalization of the dynamic contractions. During the working sets, repetitions of each set were divided into quartiles and raw EMG signal was converted into RMS values for each quartile. The CON condition performed all 9 sets of elbow flexion with their GH joint at 0° (i.e., neutral position). The VAR condition performed 3 sets of elbow flexion in each position (−30°, 0°, 90°), in a randomized fashion. A paired t-test was used to compare volume load and muscle activation between conditions. The significance level was set at p < 0.05. Results: For muscle activation, the overall session EMG amplitude was significantly higher (p = 0.0001) in the VAR condition compared to CON (CI: 8.4–23.3%). Interestingly, regarding volume load, there were no differences between conditions (VAR 596 kg ± 170, CON 606 kg ± 175). Conclusion: Our results suggest that despite similar volume load between conditions, varying joint angles increases muscle activation within a training session. Practical Applications: Our data suggest that altering joint angles during exercise increases muscle activation in an acute fashion. However, these findings should be examined with caution since these acute responses may not be associated with long term adaptations. Therefore, future investigations are warranted to determine any chronic effects.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Establishing Effectiveness of Muscle Recruitment in a Medicine Ball Versus a Ballistic Ball During Upper Extremity Exercise

H. Milton,1 A. Davis,2 and J. Fernandes2

1NYU Langone Sports Performance Center; and 2NYU Langone Health

Background: Various exercise tools are used in abundance during training and rehabilitation of athletes susceptible to shoulder injury as a means to strengthen stabilizing muscles of the shoulder, and trunk. In contrast to the vast amount of literature evaluating muscular activity during traditional medicine balls and Bodyblade tools, there is no peer reviewed literature evaluating muscular activity during exercise using new varieties of medicine balls that are currently being sold to rehabilitation and exercise professionals. Purpose: The purpose of this study was to compare the electromyogram (EMG) activity of shoulder and trunk stabilizing muscles during 3 commonly performed medicine ball exercises using both a standard medicine ball and a ballistic medicine ball (SB). Methods: Twenty-four healthy volunteers (17 female and 7 male) with a mean (±standard deviation) age of 35.5 ± 9.2 years and a body mass index (BMI) of 22.7 ± 2.8 were enrolled. Following a familiarization session, wireless surface EMG probes were placed on subject's infraspinatus (IS), latissimus dorsi (LD), anterior deltoid (AD) and external obliquus (EO). The order of exercises and ball selection were randomly drawn. Each subject performed 3 exercises using MB and SB. Results: There were no significant (p > 0.05) differences in maximal and mean muscle activity in any muscle group between exercises with the MB and SB. Two-way analyses of variance showed no significant (p < 0.05) differences in muscle activity between the 2 ball types for all muscle groups. Conclusion: This study suggests that the new SB exercise tool may be a useful tool for rehabilitation of athletes in need of tools to aid in shoulder and trunk stabilization. The lack of statistical significance between ball types suggests there is no added benefit to use the SB over traditional MB. Future study is recommended using a variety of SB and MB weights and sizes to further evaluate muscle recruitment during common exercises using these tools. Practical Applications: Rehabilitation therapists and exercise professionals alike may further consider utilizing newly marketed exercise tools not as a replacement of traditional tools, but rather as a compliment for training variety in athletes.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Comparison of Stride Length and Stride Frequency Patterns of Sprint Performance in Overground vs Motorized Treadmill Sprinting

L. Gruber, S. Montalvo, and S. Dorgo

University of Texas at El Paso

Sprint Performance (SP) and the ability to attain maximal sprinting velocity is a major factor in many athletic events. Stride length (SL) and stride frequency (SF) are critical variables when looking at SP. SP can be improved by training overground (on track) (OG), as well as on motorized high-speed treadmills (TM). However, our current understanding is lacking regarding kinematic differences, specifically SL and SF patterns, between motorized treadmill and overground sprinting conditions. Purpose: (a) To examine the relationship between SL and SF between OG and TM sprinting; and (b) examine if SL and SF are predictors of OG and TM maximal sprint speeds. Methods: Forty subjects, 20 NCAA sprint athletes and 20 recreationally trained college-aged athletes took part in a single-day testing session. Testing consisted of two 60 m OG sprints and 2 maximal sprints on a highspeed motorized treadmill. In addition to SL and SF, contact time (CT), and flight time (FT) were recorded using a photoelectric cells device. For the OG testing, 2 timing gates were also used to record maximal sprint speed over the final 10 m of each 60 m sprint. Subjects were instructed to use the 50-m prior to the testing zone for acceleration in order to achieve maximal speed. For the TM sprinting testing, a motorized treadmill with a max speed of 13.5 m/s was used. Subjects wore a safety harness connected to a steel frame to prevent being ejected from the treadmill. In the testing run, subjects were instructed to gradually transfer their weight on to the moving belt while holding onto the handrails. Subjects were asked to keep up with the belt speed for 3–4 seconds. If successful, belt speed was increased for the subsequent trials until the subjects' failure to keep up. Results: Among the 40 subjects, there was a strong positive correlation for speed, CT, and SF performed in OG modality. A correlation was also found between speed, CT and SF performed in the TM condition (Pearson R = 0.94; R = 0.68; and R = 0.65, respectively). In addition, we observed a significant difference (p = 0.00) between OG-speed & TM speed (mean and SD diff = −0.214 ± 0.384), OG-CT & TM-CT (mean and SD diff = −0.010 ± 0.020), and OG-SF & TM-SF (mean and SD diff = −0.471 ± 0.311). No significance difference was observed between OG-FT & TM-FT (mean and SD diff = −0.101 ± 0.248) and OG-SL & TM-SL (mean and SD diff = −65.325 ± 95.750). Among 40 subjects, CT, FT, and SF were found to be predictors of sprint speed in the overground modality (p = 0.000) while SL was not a predictor of sprint speed in this modality. Linear regression for motorized treadmill conditions in 40 subjects showed that CT, FT, SL and SF are all predictors of sprint speed (p < 0.05). Conclusion: Results show that motorized treadmill increases stride frequency dramatically when compared to overground, which could result in the motorized treadmill being used as a training tool to enhance stride frequency. However, the optimal ratio used to achieve sprint speed was altered on the motorized treadmill when compared to overground running. Therefore, while there may benefits to using such an instrument to enhance speed, it is unclear how much improvement is transferred to overground condition. Practical Applications: A High-speed motorized treadmill can be used as a supplemental training tool to induce supramaximal sprint running, in aid of acquiring neural muscular adaptations and improvement of stride frequency and ground contact time.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Effects of Instability Devices on Muscular Activation During Performance of a Glute Bridge Exercise

T. Huckaby, B. Hirt, S. Moreno, and L. Atkins

Angelo State University

Purpose: Exercises performed on an unstable surface have been associated with increased upper and lower extremity muscle activation compared to exercises performed on stable surfaces. Additionally, altered trunk and lower limb muscle activation has been associated with various pathological conditions. Subsequently clients are commonly prescribed a variant of the glute bridge exercise in an effort to optimize trunk and lower limb muscle function; however, currently little is known about the influence of varying levels of surface stability on muscle activation when performing the glute bridge exercise. Thus, the purpose of this study was to examine the effects of varying surface stability during the glute bridge exercise on trunk and lower limb muscle activation. Methods: Twenty-two asymptomatic, physically active subjects (10 female) participated in this study (age: 24.2 (1.6) yr, body mass index: 24.4 (3.0) kg/m2). To be included, subjects were required to correctly perform 5 repetitions of the glute bridge exercise on a stable surface. Subjects were excluded if they: (a) had a BMI greater than 30 kg/m2, (b) had surgery within year prior to testing, (c) were injured within 6 months prior to testing, or (d) were pregnant. Surface electromyography was used to record (1,000 Hz) activation of the rectus abdominis (RA), external oblique (EO), gluteus maximus (GM) and biceps femoris (BF) for one second during a static glute bridge exercise performed during 3 conditions that varied according to surface stability. These conditions included a stable box (CTRL), swiss ball (SB), and suspension straps (SS). The dependent variables included the 5-trial averages of mean muscle activation during each condition. One-way repeated ANOVAs and Tukey LSD post hoc tests (for significant ANOVAs) were calculated (α = 0.05) to determine the effect of surface stability on muscle activation. Results: Mean activation of the BF was similar across all conditions (p > 0.05). Compared to the CTRL condition, RA and EO activation increased during the SB (p < 0.01) and SS conditions (p < 0.01). Compared to SS condition, GM activation decreased during the SB (p < 0.01) and CTRL (p < 0.01) conditions. Conclusion: Findings from the current study indicate that a glute bridge exercise performed on an unstable (vs stable) surface elicits increased trunk and lower limb muscle activation. Furthermore, the SS condition resulted in greater GM activation than the CTRL and SB conditions. Practical Applications: Use of instability devices should be considered when prescribing the glute bridge exercise to increase trunk and lower limb muscle activation in clinical settings. Clients with low back pain, osteoarthritis, knee pain, and gait abnormalities associated with reduced GM activation may benefit from progression to the SS variation of the glute bridge.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Prediction of Bat Swing Velocity From Sprint Speeds and Discrete Variables of the Countermovement Jump in NCAA Division 1 Softball

B. Mann, J. Mayhew1, B. Ruhanen2, and J. Dawes

1Truman State University; and 2University of Missouri

A primary requirement for scoring runs in softball is being able to hit the ball. Given the speed of most pitches, the ability to generate speed in the bat swing would appear to be one of the major components of hitting the ball. Purpose: The purpose of this study was to determine the ability to predict bat velocity from commonly utilized discrete variables of the countermovement jump. Methods: Members of an NCAA Division 1 softball team (n = 22, age = 19.05 ± 1.16 years, height = 170.2 ± 6.3 cm, body mass = 66.86 ± 9.91 kg) were measured for countermovement jump (CMVJ) on a single-axis dual-force platform system sampling at 1,000 Hz. Players stood motionless with hands on hips for 3 seconds to determine body mass. Upon command, players jumped as high as possible with hands remaining on hips. Subjects stood still for quiet standing to record mass and have a reference point for the jump. Upon landing, the player re-centered her feet on each platform and achieved quiet standing for 1 full second before repeating the CMVJ. Peak vertical velocity (PVV), force at peak power (FPP), peak power (PP), and time to peak power (TPP) were processed with commercially available software. The better repetition was selected for analysis. Two 20-yd sprint trials were performed from a standing start with 10-yd split time taken using an infrared timing system; the better trial was selected for analysis. Bat velocity (BV) was recorded utilizing a previously validated commercially available accelerometer that attached to the proximal end of the bat. The average of 8 repetitions was used to represent BV. Results: Backwards elimination regression using CMVJ variables and sprint times were used to estimate BV. FPP was the only variable selected to predict BV (R = 0.79, SEE = 3.77, BV (m/s) = 121.625 – FPP (N) × 0.039). Conclusion: These results suggest that a softball player's BV is predominantly dependent on her ability to generate force quickly. Practical Applications: The findings in this study suggest the potential of increasing BV by increasing leg strength and/or leg power in softball players. A longitudinal study is necessary to validate this supposition.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Reliability and Precision of Frontal-Plane Knee Angulation Measures During Vertical Jumping

L. Weiss, H. Daugherty, D. Powell, M. Paquette, and L. Allison

The University of Memphis

Knee actions primarily occur through sagittal (flexion and extension), and to a lesser extent, transverse (internal and external rotation) planes. However, slight frontal-plane movements are also possible ranging from varus (bowed knees) to valgus (knock knees) positions. When frontal-plane malalignment is substantial and superimposed on sagittal- and/or transverse-plane movements, knee structures may be exposed to unusual stresses and performance might be affected. To address these scenarios during exercise, objective measures of frontal-plane knee positions are needed. Purpose: To determine the stability reliability and precision of frontal-plane knee angle measures during sagittal-plane vertical jump performance. Methods: Subjects were 60 young adults (31 men, 29 women). All were fitted with reflective anatomical markers to define and track the right side of the pelvis and lower extremity during 3 constrained-arm-swing countermovement vertical jumps (CMVJ) that incorporated self-selected countermovement depths. Three-dimensional joint kinematics were collected using an 8-camera motion capture system at a sampling rate of 240 Hz, proprietary software, and a USB analog acquisition interface. Additional proprietary software was then used to process 3D joint angles using an 8 Hz lowpass filter (knee frontal plane measures reported herein). Data were analyzed for the highest jump from each of 2 identical sessions. Frontal-plane knee alignment angles were obtained for the right lower limb during jumping at the following positions: 1) end of the countermovement, 2) peak knee adduction, 3) take-off, and 4) peak knee abduction. In addition, maximum frontal-plane knee excursion was calculated as the difference between peak adduction and peak abduction. Stability reliability was determined using an intraclass correlation coefficient (ICC, two-way random model), and precision using both the standard error of measurement (SEM) and the coefficient of variation (CV%). Statistical analyses were performed for all subjects, as well as separately for men and women. Results: Study findings are presented in Table 1. Conclusion: Stability reliability was moderate and precision poor for all designated frontal plane angular measures for men and women during CMVJ. Practical Applications: Because of poor precision, averaging frontal-plane knee angles over multiple sessions may be appropriate when interpreting output. Variations in reflective marker placements need to be meticulously avoided.

table1
Table 1.:
Frontal plane angles during countermovement vertical jumping (all subjects/men/women).

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Countermovement Jump Qualities of Elite Academy Rugby Union Players

C. Owen,1 K. Till, P. Phibbs,1 D. Read,1 J. Weakley,1 M. Atkinson,2 K. Stokes,2 S. Williams,2 S. Kemp,3 and B. Jones

1Leeds Beckett University; 2University of Bath; and 3Rugby Football Union

Purpose: Identify positional kinetic and kinematic countermovement jump (CMJ) variables of elite Under 18 (U18) academy rugby union players. Methods: With ethics approval, 166 U18 male rugby union players (front row n = 35; second row n = 16; back row n = 40; half backs n = 34; centres n = 15; back 3 n = 26) from 6 English Regional Academies (age 17.3 ± 0.7 years; height 181.0 ± 8.3 cm; body mass 88.6 ± 14.2 kg) participated in the study. Participants completed 2 maximal CMJ on 2 portable force platforms (Pasco PS-2141, Roseville, CA, USA) sampling at 500 Hz. The mean of the 2 trials was used for analysis. Following the testing a custom-designed R-script was used to find kinetic (peak force, mean rate of force development, impulse, peak power and total area under the force velocity curve) and kinematic variables (take-off velocity, jump height, centre of mass displacement and reactive strength index modified) for each jump identifying eccentric and concentric jump phases where applicable. Principal component (PC) analysis was conducted to identify the variance explained by the variables and collinearity. From the first 3 PCs (i.e., power and force variables [PC1; 35%], impulse [PC2; 27%] and velocity [PC3; 25%]), variables with the greatest loading factors were selected for analysis using a one-way ANOVA and Tukey Kramer post hoc (α = 0.05) to identify positional differences once normality had been assured. Results: Significant between position differences were observed for area under the force velocity curve (F(5,160) = 4.851, p = < 0.001), concentric impulse (F(5,160) = 21.91, p = < 0.001) and take off velocity (F(5,160) = 10.18, p = < 0.001). Positional data and significant post hoc differences are shown in Table 1. Conclusion: These findings suggest that kinetic and kinematic characteristics in the CMJ vary by playing position in U18 academy rugby union players. Heavier front row and second row forwards produced greater area under the force velocity curve especially when compared to half backs. Centres were able to produce similar area under the force velocity curve to the front row, however along with the rest of the backs and back row, a significantly lower concentric impulse is observed potentially due to lower force producing capabilities or a shorter force application time. In contrast, all positions except for the second row achieved significantly higher take-off velocities than the front row, with back 3 players achieving the greatest velocity. Practical Applications: It is essential for practitioners to develop physical qualities that are specific to a given athlete and their role in competition. Results from the present study suggest that a multivariate approach may provide additional information for monitoring neuromuscular performance. The positional differences observed in this study should be combined with knowledge of match demands to determine a suitable training intervention for U18 rugby union players.

table2
Table 1.:
A comparison of the highest loading variables for each principal component between playing positions for U18 academy rugby union players (mean ± SD).

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Functional Movement Patterns and Perceived Mobility in Collegiate Lacrosse Athletes

C. Rosenborough, S. Collins, E. Smith, and T. Bowman

University of Lynchburg

The stress on the body from sport participation may play a role in an athlete's ability to function throughout a season. Purpose: To examine the effects of a non-traditional lacrosse fall season on functional movement patterns for both males and females, while secondarily observing how collegiate lacrosse athletes perceived mobility. Methods: Fifty males (age = 19.38 ± 1.24 years, height = 182.63 ± 6.16 cm, mass = 82.37 ± 8.46 kg) and 22 females (age = 19.68 ± 1.17 years, height = 165.10 ± 6.88 cm, mass = 64.09 ± 8.72 kg) who participated on National Collegiate Athletic Association Division III lacrosse teams volunteered to participate. The independent variable was time (pre, post). Pre- and post-test mobility scores were measured 2 weeks before and after the season, respectively. Main outcome measures included functional mobility and perceived mobility scores. We measured perceived mobility postseason using functional movements by asking participants to grade themselves on each movement. Data was analyzed using a 1-way repeated measure ANOVA for each sex separately. A chi-square analysis was used to determine the change in asymmetry frequency. We set an alpha value of 0.05 for significance. Results: Time significantly increased female mobility scores from preseason (mean = 15.27 ± 2.25) to postseason (mean = 16.05 ± 1.50; F1,21 = 4.46, p = 0.05, η2 = 0.18). However, males' total mobility scores did not significantly differ from preseason (mean = 15.60 ± 1.86) to postseason (mean = 15.64 ± 1.71; F1,49 = 0.03, p = 0.87, η2 = 0.001, 1-β = 0.05). There was not a significant difference in the number of male (preseason = 8, postseason = 4; η21 = 2.38, p = 0.12) or female participants (preseason = 5, postseason = 1; η21 = 2.15, p = 0.14) that recorded a total mobility score below the injury risk cut off of 14 at the end of the season. Time significantly increased the number of male athletes with an asymmetry on the hurdle step (preseason N = 2, postseason N = 9; η21 = 25.52, p < 0.001), inline lunge (preseason N = 10, postseason N = 20; η21 = 12.50, p < 0.001) and shoulder mobility (preseason N = 4, postseason N = 21; η21 = 78.53, p < 0.001) while male active straight leg raise asymmetries decreased (preseason N = 26, postseason N = 8; η21 = 25.96, p < 0.001). Significant differences in male measured score and perceived mobility scores were found in all movements except for right shoulder mobility (p = 0.82) and right active straight leg raise (p = 0.05). Conclusion: An 8-week fall lacrosse season has significant effects on functional movement in various areas. These changes may lead to alterations in the kinetic chain resulting in joint hypomobility, hypermobility and compensatory patterns. Practical Applications: The results of this study indicate that mobility changes in both male and female lacrosse athletes over the course of a season in different areas. Sports medicine and strength and conditioning professionals should be aware of male athletes overestimating self-reported mobility and therefore not addressing deficits independently.

F6
This table demonstrates the difference between measured mobility perceived mobility and between all groups.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

The Effects of Concurrent Activation Potentiation on Average and Peak Power During Submaximal Deadlift Exercise

C. Allen,1 E. Recanzone,2 and A. Bittinger

1Florida Southern College; and 2Florida Southern College

Concurrent activation potentiation (CAP) is the ergogenic phenomenon of increased agonist muscular and performance characteristics achieved through remote voluntary contractions (RVC) performed simultaneously with prime mover activation. Research examining CAP has focused primarily on muscular force production characteristics and not on power output. Given the purported ergogenic benefits, the influence of CAP on power output warrants investigation. Purpose: The purpose of this study was to examine the effects of maximal jaw clenching and maximal jaw opening on average and peak power output during the deadlift exercise against a submaximal resistance. Methods: Eight male (age 21.75 ± 2.87 years; height 179.86 ± 5.6 cm; mass 83.05 ± 8.00 kg) and 9 females (age 20.11 ± 1.05 years; height 162.28 ± 8.54 cm; mass 61.66 ± 9.41 kg) considered intermediate to advanced resistance trained athletes visited the lab on 2 occasions. The first visit involved provision of written consent, one repetition maximum (1RM) deadlift assessment, and familiarization with subsequent data collection procedures. The second visit, which occurred between 72 hours and one week following the initial visit, consisted of submaximal deadlifts at 65% of 1RM performed under 3 experimental conditions: jaw maximally clenched, jaw maximally opened, and jaw relaxed (control condition). Experimental conditions were counterbalanced between subjects to eliminate possible order effects. Subjects were instructed to initiate the experimental condition simultaneously with maximal force application to the bar, and to complete the concentric phase of the deadlift as fast as possible. Average and peak barbell movement velocity was recorded with a Tendo Power & Speed Analyzer (Tendo Sports Machines, Slovak Republic). Three trials were performed under each condition, and velocity measurements from each trial were averaged. A 1 × 3 repeated measures ANOVA was used to determine if a difference between conditions existed. Pairwise comparisons with Bonferroni adjustment determined specific differences between groups. Results: There was a statistically significant difference between conditions for both average (p = 0.016) and peak (p = 0.014) power. Pairwise comparisons demonstrated that maximum jaw clenching (p = 0.031) and maximum jaw opening (p = 0.012) significantly improved peak power output when compared to the jaw relaxed condition. Additionally, maximal jaw clenching (p = 0.101) and maximum jaw opening (p = 0.011) improved average power output in comparison to the jaw relaxed condition, however, only the maximal jaw opening condition was statistically significant. Conclusion: Both clenching and opening the jaw maximally, enhances power output during submaximal resistance exercise. Although the proposed use of maximal jaw opening as an RVC is relatively new, it may be more effective at provoking CAP than maximal jaw clenching. Practical Applications: CAP produced by maximal jaw muscle activation improves average and peak power output during resistance training exercise. Coaches can encourage athletes to incorporate maximal jaw clenching or opening as an acute performance enhancing strategy during strength and conditioning training activities.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Concurrent Activation Potentiation Improves Barbell Velocity During Submaximal Deadlift Exercise

E. Recanzone1, A. Bittinger, and C. Allen2

1Florida Southern College; and 2Florida Southern College

The acceleration of an object will increase as net force applied to the object increases. This increase in acceleration will increase the object's movement velocity. Concurrent activation potentiation (CAP) is the ergogenic advantage of increased agonist muscular and performance characteristics attained through simultaneous activation of musculature not involved in the activity of interest. Research examining the CAP phenomenon has focused primarily on muscular activation and force production characteristics. The influence of CAP on exercise movement velocity remains unclear. Purpose: The purpose of this investigation was to examine the impact of CAP, achieved via maximal jaw clenching and maximal jaw opening, on barbell movement velocity during the deadlift exercise with submaximal resistance. Methods: Eight male (age 21.75 ± 2.87 years; height 179.86 ± 5.6 cm; mass 83.05 ± 8.00 kg) and 9 females (age 20.11 ± 1.05 years; height 162.28 ± 8.54 cm; mass 61.66 ± 9.41 kg) considered intermediate to advanced resistance trained athletes visited the lab on 2 occasions. The first visit involved provision of written consent, one repetition maximum (1RM) deadlift assessment, and familiarization with subsequent data collection procedures. The second visit, which occurred between 72 hours and one week following the initial visit, consisted of submaximal deadlifts at 65% of 1RM performed under 3 experimental conditions: jaw maximally clenched, jaw maximally opened, and jaw relaxed (control condition). Experimental conditions were counterbalanced between subjects to eliminate possible order effects. Subjects were instructed to initiate the experimental condition simultaneously with maximal force application to the bar and to complete the concentric phase of the deadlift as fast as possible. Average and peak barbell movement velocity was recorded using a Tendo Power & Speed Analyzer (Tendo Sports Machines, Slovak Republic). Three trials were performed under each condition, and velocity measurements from each trial were averaged. A 1 × 3 repeated measures ANOVA was used to determine if a difference between conditions existed. Pairwise comparisons with Bonferroni adjustment determined specific differences between groups. Results: There was a statistically significant difference between experimental conditions for both average (p = 0.003) and peak (p = 0.01) velocities. Pairwise comparisons demonstrated that maximum jaw clenching (p = 0.042) and maximum jaw opening (p = 0.002) significantly improved average movement velocity when compared to the jaw relaxed condition. Maximal jaw clenching (p = 0.061) and maximum jaw opening (p = 0.006) also improved peak movement velocity in comparison to the jaw relaxed condition, however, only the maximal jaw opening condition was statistically significant. Conclusion: CAP achieved by maximally clenching or opening the jaw is effective at enhancing barbell movement velocity during the submaximal deadlift exercise, presumably by augmenting agonist muscular force production characteristics. Maximal jaw opening is just as effective at inducing CAP if not more so, than maximal jaw clenching. Practical Applications: Maximally activating jaw musculature to either clench or open the jaw is effective at eliciting CAP to enhance performance. Strength and conditioning professionals may encourage maximal jaw clenching and opening during resistance training exercises to enhance force production and movement velocity.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

The Effects of Concurrent Activation Potentiation on Bat Swing Velocity of Division II College Softball Athletes

A. Mace, S. Terrell, Z. Wallace, and C. Allen

Florida Southern College

Concurrent activation potentiation (CAP), achieved by remote voluntary contractions (RVC) such as jaw clenching, has been proposed to enhance performance in male but not female athletes. CAP has been shown to enhance muscular performance characteristics, yet its effects on sports performance outcomes such as bat swing velocity (BSV), which is an important component for successful hitting in softball, has not been investigated. Furthermore, it remains unclear as to whether RVC produces a similar ergogenic effect in women as it does in men. Purpose: The purpose of this research was to examine the effects of maximal jaw clenching on bat swing velocity in collegiate division II softball players. Methods: Thirteen (n = 13) division II softball players (age 19.79 ± 1.31 years; height 167.69 ± 6.91 cm; mass 68.23 ± 8.68 kg) volunteered to participate in this study. Subjects were instructed to complete their normal warmup routine as if preparing for a game at-bat. Following the warmup, subjects completed 10 maximal effort swings targeting a softball on a tee. Five swings were performed while maximally clenching the jaw and 5 with relaxed jaw musculature (control condition). Conditions were counterbalanced between subjects to account for possible order effects. Each subject was given 30 seconds of rest between swing attempts. Tee height, tee placement, and bat used varied between subjects but remained consistent for all swing attempts. BSV was recorded using an inertial measurement unit (Zepp Sensor, Zepp Labs, Inc.) attached to the knob of the bat, and all recorded trials were averaged for analysis. Paired sample t-tests were utilized to determine differences between jaw clenched and jaw relaxed conditions. Results: Mean swing velocity for the control condition was 28.02 m/s (62.68 mph) and 29.42 m/s (65.82 mph) for the jaw clenched condition, producing a statistically significant mean difference of 1.4 m/s (3.14 mph) (p = 0.003). Conclusion: Maximally clenching the jaw while swinging a softball bat is a useful strategy to improve BSV in Division II college softball players. Additionally, CAP via maximal jaw clenching appears to improve aspects of athletic performance in female athletes. Practical Applications: CAP, achieved by maximally clenching the jaw, is a practical and legal ergogenic strategy to produce increased BSV in female athletes. Since BSV is an important component of successful hitting, coaches may encourage softball athletes to incorporate this RVC technique in their hitting approach as the increase in BSV could positively influence hitting performance.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Neuromuscular Responses in Unilateral Strength Discrepancies Within the Lower Limb Bilateral Deficit

M. Byrd1, T. Dinyer1, P. Succi1, and H. Bergstrom2

1University of Kentucky; and 2University of Kentucky

The bilateral deficit (BLD) is the phenomenon in which the sum of the forces produced unilaterally (right and left separately) is greater than the force produced bilaterally (right and left together) during maximal contractions of the limbs. Bilateral contractions within the lower limbs have previously resulted in lower or no differences between the neuromuscular responses of the limbs. Thus, there are limited and conflicting data regarding neuromuscular responses during the assessment of the bilateral deficit. Purpose: This study examined the neuromuscular responses within subjects that demonstrated a lower limb BLD accompanied by the presences of strength discrepancies between the lower limbs during the unilateral muscular strength assessments. Methods: Nine (male: n = 6; female: n = 3) subjects (mean ± SD age: 24.4 ± 4.6 years, height: 178.0 ± 7.7 cm, body mass: 80.0 ± 11.1 kg) completed randomized, isometric, seated leg extension bilateral and unilateral maximum voluntary isometric contractions (MVIC) followed by randomized, bilateral and unilateral dynamic, seated leg extension for the determination of the 1 repetition maximum (1RM) strength. The magnitude of the BLD was assessed using the bilateral index (BI [%] = (100 × (bilateral strength/right unilateral + left unilateral) − 100). The electromyographic (EMG) and mechanomyographic (MMG) amplitude (AMP) and mean power frequency (MPF) were measured from the vastus lateralis of the right and left lower limbs during the MVIC and 1RM trials. The 1RM neuromuscular signals were normalized to the corresponding signals recorded during the MVIC trials. Statistical analyses included paired samples t-test (p ≤ 0.05). Results: The lower limb BLD resulted in a BI of −8.7% ± 4.2%. Among the unilateral strength measures, each subject presented with a lower limb unilateral strength discrepancy (p = 0.00008; strong limb (SL) 40.7 ± 8.2 kg, weak limb (WL) 37.3 ± 7.7 kg). The SL had a significantly greater EMG AMP (p = 0.04), compared to the WL during the unilateral dynamic, seated leg extension 1RM measure, however, there were no difference in EMG AMP between the SL and WL during the bilateral dynamic (p = 0.1), seated leg extension 1RM measure. There were no differences for the EMG MPF, MMG AMP, or MMG MPF for either the unilateral or bilateral dynamic, seated leg extension 1RM measure. Conclusion: These findings indicated the lower limb unilateral strength discrepancies within subjects with a lower limb BLD could be due to greater global motor unit activation in the SL compared to the WL during unilateral movements. Practical Applications: When measuring bilateral strength, it cannot be assumed each limb is contributing evenly and it may be beneficial to take into account any unilateral strength discrepancies that are present. Training for improvement of any unilateral strength discrepancies may also carry over to greater bilateral strength improvements.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Assessing the Impact of Vibration on Rectus Femoris During a Bodyweight Squat: A Pilot Study

M. McDermott, E. Hutton, S. Yamasaki, S. Arter, J. Glauser, J. Schoffstall, A. Bosak, and R. Lowell

Liberty University

Whole-body vibration (WBV) exposes the entire body to mechanical oscillations while the subject is standing on a platform. WBV has emerged as a training and rehabilitation modality in recent years. Therefore, evaluating the use of vibration in a performance setting is crucial. Prior research has assessed electromyographic response of the quadricep and hamstring muscles using vibration during static squat exercise, however, to the best of the researchers' knowledge, no research has been conducted to assess the activity of the rectus femoris using WBV during the dynamic squat movement. It is hypothesized that the vibrations of the platform will cause increased motor unit recruitment, causing the rectus femoris to produce a higher root mean squared (RMS) value when compared to the RMS value without vibration. It is logical to assume that greater RMS values during WBV could indicate the recruitment of more motor units during exercise with this modality. Purpose: To compare electromyographic (EMG) output values of the rectus femoris during the whole-body squat (WBS) with WBV vs. output during WBS without WBV. Methods: After completing a PAR-Q and informed consent form, and prior to any testing, subjects were asked to remove their shoes in order to eliminate the variability that different footwear may have had on the potential results. FMS deep squat protocol was used to assess 14 Division 1 NCAA track and field athletes (8 male, 6 female) for adequate squat form. Following a dynamic warm-up protocol, a wired EMG sensor was placed on the right leg over the rectus femoris muscle belly. Subjects performed 15 repetitions of WBS on the ground, followed by an eight-minute rest period. Subjects then performed 15 repetitions of WBS on a WBV platform vibrating at a frequency of 40 MHz. Throughout testing, EMG data was collected. The RMS value was recorded from both trials for each subject. RMS values for WBS during trials with and without WBV for each subject were compared using a Paired-Samples t-Test with an alpha level at p ≤ 0.05. Results: WBV values were significantly greater than ground squat values regarding mean RMS (96.7 ± 33.7 vs. 74.6 ± 28.7 µV, p < 0.01). Conclusion: A significantly greater RMS value during WBV trials possibly indicates that the rectus femoris was more active when performing WBS with WBV. Practical Applications: A significant increase in muscle activity of the rectus femoris during the WBV trial potentially suggests that more motor units are recruited when the body is experiencing WBV. Higher levels of muscle activity in an equal amount of time provides evidence that WBV may be a more efficient form of training. Further research should be completed with a larger sample size and with a focus on the separation of genders in order to examine the effects of WBV on muscle activity.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

The Effects of a Vertical Jump Fatigue Test on Lactate Production and Heart Rate

E. Mosier,1 A. Fry,2 J. Nicoll,3 and S. Sontag2

1Northwest Missouri State University; 2University of Kansas; and 3California State University, Northridge

There are numerous anaerobic tests that use different modes of exercise or movement patterns, while also varying in duration, which can help assess anaerobic endurance. Purpose: This study examined the effects of a vertical jump fatigue test on blood lactate (HLa) concentrations and heart rate (HR) in men and women. Methods: Healthy, recreationally active women (±SD; n = 11, age = 20.8 ± 1.1 years, hgt. = 172.2 ± 7.4 cm, wgt. = 68.0 ± 7.2 kg) and men (n = 11, age = 23.0 ± 2.6 years, hgt. = 180.3 ± 4.8 cm, wgt. = 80.4 ± 7.3 kg) served as subjects. Each subject completed 2 randomized experimental sessions (i.e., control session (CON), and VJ fatigue protocol). During the VJ test each subject was instructed to bend the knee to 90° and jump explosively and repeat immediately on landing for a total of 5 sets. Each set consisted of 15 seconds jumping, 15 seconds rest, 15 seconds jumping, and 15 seconds rest. During the CON session each subject would sit relaxed for 15 minutes. A uni-axial force plate and a data acquisition system sampling at 1,000 Hz was used to monitor the ground reaction forces. HR was collected pre-test and post-test with a chest monitor strap. Each subject provided blood samples at Baseline (arrival), Pre (5 minutes pre-test), and Post (2.5 minutes post-test). Samples were analyzed with a Lactate Plus blood lactate analyzer. Three-way repeated measures ANOVAs (sex × condition × time) were performed on HLa and heart rate. Paired samples t-tests were used to examine the differences in flight times and positive impulses of the second jump of set 1 and last jump of set 10 during the VJ test. These VJs were selected to include the preceding VJ rebound and the next CMVJ. Post hoc comparisons were conducted when needed using the Bonferroni correction. The level of significant was set to p ≤ 0.05 for the statistical tests. Results: The ANOVAs indicated a significant 3-way interaction (condition × sex × time) for HLa concentrations (p < 0.01), and a significant 2-way interaction (condition × time) for HR (p < 0.01). Follow-up analyses indicated significant differences between pre-and post-tests for HLa concentrations. Paired samples t-tests indicated a significant interaction for flight time and positive impulse between set 1 and set 2 jumps for both men and women (Table 1). Conclusion: The results indicated the modified VJ test induced fatigue responses in both men and women as indicated by the significantly increased HLa and HR responses. In addition, flight time and positive impulses indicated individuals spent more time on the ground and less time in the air. Practical Applications: The current study evaluated a potential testing method to help evaluate anaerobic fatigue. This may provide the strength and conditioning professional helpful longitudinal information as an athlete progresses through a training program and season.

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Thursday, July 11, 2019, 12:00 pm–1:30 pm

Does Regular Resistance Training Improve Lower-Extremity Functionality in Competitive Cheer and Dance Athletes?

Q. Johnson,1 C. Anthony,1 C. Diehl, M. Snow,2 and D. Smith

1Oklahoma State University; and 2Midland University

Movement assessments are often used as components of strength and conditioning, as well as athletic training programs in order to determine biomechanical efficiency, movement limitations, and to assist in developing corrective exercise protocols. Although there is extensive research on Functional Movement Screen (FMS) performance in athletic populations, very few have examined the variables that may affect such in competitive cheer and dance athletes. We hypothesized that regular participation in resistance training programs would significantly improve lower-extremity functionality and performance on the FMS assessment. Purpose: To compare differences in lower-extremity functionality between resistance trained (RT) versus non-resistance trained (NRT) competitive cheer and dance athletes by utilizing 5 components of the FMS; deep squat (DS), hurdle-step (HS), in-line lunge (ILL), active straight leg raise (ASLR), and total score (TS). Methods: Fifty-three competitive cheer and dance athletes (RT = 33, NRT = 20) volunteered for this study. Athletes in the RT group participated in an undulating resistance training program at least 2–3 days per week for ≥16 weeks, while athletes in the NRT group did not participate in resistance training. Athletes had their movement ability assessed by FMS certified personnel prior to beginning their competitive season. Each participant was briefed and provided with proper instruction prior to performing each movement. All data was analyzed using PASW software version 24.0 (SPSS Inc, Chicago, IL, USA). The University Institutional Review Board for human subject's research approved this study and all subjects signed a written informed consent document prior to participation. Separate 1-way ANOVAs were run for each dependent variable. Results: A significant interaction was observed for TS between RT and NRT groups (p = 0.000). Additionally, the RT performed significantly better on the DS (p = 0.000), HS (p = 0.011), ILL (p = 0.038), and ASLR (p = 0.036) when compared to the NRT group. Conclusion: This study observed significant differences in FMS performance in RT versus NRT cheer and dance athletes. This suggests that an increased exposure to resistance training is beneficial for improving the functional biomechanics involved in lower-extremity dominant movements. Practical Applications: Introducing resistance training into training protocols may be an effective method for improving functional movement capacities, which may translate to increased execution of sport-specific movements.

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Thursday, July 11, 2019, 12:00 pm–1:30 pm

Does Age-Related Loss of Muscle Size and Motor Units Affect the Speed of the Sensorimotor Integration: A Pilot Study

T. Blackstock,1 M. Magrini,2 R. Colquhoun,3 M. Ferrell,1 S. Fleming,1 N. Jenkins,1 and J. DeFreitas4

1Oklahoma State University; 2Creighton University; 3University of South Alabama; and 4OKlahoma State University

The reactive leg drop (RLD) is a novel assessment designed to examine the rapid sensorimotor integration necessary to recover from a slip and avoid a fall. Previous research has suggested that the age-related loss of muscle mass and functioning motor units may be a leading cause of non-workplace related falls. Purpose: Therefore, the purpose of this pilot study was to evaluate age-related differences between and relationships among measures of muscle size, motor unit number estimation (MUNE), and speed of sensorimotor integration. Methods: Seventeen (Young: n = 9, 22 ± 3 years; Older: n = 8, 71 ± 5 years) adults participated in this study. For the RLD, participants were seated with their eyes closed while the investigator held their leg in full extension (180°) with an elastic band. The researcher released the band once their leg was fully relaxed. The participants were instructed to kick back up as fast as possible once they felt their leg falling. The drop angle was measured with an electro-goniometer secured to the participant's knee and calculated as the difference between the starting position and the lowest point reached before the participant kicked their leg back up. The muscle cross-sectional area of the vastus lateralis (VL mCSA) was examined using an ultrasound. MUNE was calculated as the ratio of the ensemble average of the single motor unit potential amplitude to the compound muscle action potential amplitude and was corrected for alternation. Independent samples t-test were used to analyze age differences in RLD drop angle, VL mCSA and MUNE. Pearson correlation coefficients were used to analyze the relationships between the 3 measures. Results: Significant age differences were observed between MUNE (Y: 281.9 ± 41.4; O: 141.5 ± 27.3; p£0.001), VL mCSA (Y: 27.8 ± 4.5; O: 8.3 ± 2.8 cm2; p £ 0.001) and drop angle, (Y: 38.6 ± 8.7°; O: 69.6 ± 22.3°; p = 0.003). Further, drop angle was significantly related to VL mCSA (r = −0.64, p = 0.008) (Figure A), MUNE (r = −0.67, p = 0.005) (Figure B), and age (r = 0.64, p = 0.008). Conclusion: The significant age differences showed that older adults have smaller muscles, less remaining motor units, and a slower response to a sudden lower-body perturbation. The significant correlations suggest that smaller muscles with fewer functioning motor units are related to slower sensorimotor integration. However, caution should be taken when interpreting these results due to the limited number of participants in this initial pilot study. Practical Applications: The reactive leg drop is a robust assessment that can be quite useful for clinicians and practitioners. This novel assessment not only examines the speed of sensorimotor integration, but it may also be sensitive to sarcopenia-related changes in older adults.

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Figure 1.:
Relationships between drop angle, MUNE, and mCSA. *Significant relationship p = less than or equal to 0.05.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Quadriceps Cross-Sectional Area Is Related to Voluntary and Evoked, but Not Rapid Torque Production

H. Bryan,1 R. Colquhoun,2 P. Tomko,1 M. Magrini,3 S. Fleming,1 N. Banks,1 M. Ferrell,1 and N. Jenkins1

1Oklahoma State University; 2University of South Alabama; and 3Creighton University

Introduction: Skeletal muscle force production is a crucial aspect of many athletic events. Although not linear, it is generally accepted that there is a strong relationship between the cross-sectional area (mCSA) of a muscle and its maximal force production during voluntary contractions. However, the relationship among mCSA, a muscle's contractile properties, and the influence of a muscle's contractile properties on maximal force production remain unclear. Purpose: The purpose of this study was to examine the relationship among vastus lateralis (VL) mCSA, maximal voluntary contraction strength, and contractile torque production. We hypothesized that CSA would be related to both maximal voluntary strength and contractile torque production. Methods: Thirty-eight college-aged males (age = 23 ± 3; height = 177.2 ± 5.3 cm; weight = 87.7 ± 13.2 kg) volunteered to participate in this study. Ultrasound images of the right VL were obtained from each subject in order to quantify CSA. Contractile properties of the right quadriceps were assessed via transcutaneous electrical stimulation of the femoral nerve, and isometric peak twitch torque (PTT) and peak rate of twitch torque development (pRTTD) were calculated. Maximal voluntary torque (MVT) was also measured during a maximal isometric contraction. All measurements took place during the same visit and with the participant's knee joint set at approximately 90°. Bivariate correlations and stepwise multiple linear regression were used to examine the relationships and relative contributions of VL CSA, PTT, and pRTTD to MVT. Results: There were significant, positive relationships between VL CSA and MVT (p < 0.001; r = 0.755), VL CSA and PTT (p = 0.023; r = 0.369), and PTT and pRTTD (p < 0.001; r = 0.604). However, no significant relationships were observed between VL CSA and pRTTD (p = 0.536; r = 0.104), PTT and MVT (p = 0.07; r = 0.297), or pRTTD and MVT (p = 0.77; r = −0.05). The stepwise MLR suggested that only mCSA significantly contributed to the prediction of MVT (R2 = 0.57; beta coefficient = mCSA [0.755]). Conclusion: There was a significant, positive relationship between muscle size and voluntary and evoked strength of the quadriceps femoris in college-aged males. Furthermore, only mCSA contributed to the prediction of MVT in our sample. Moreover, there was no relationship between mCSA and pRTTD. Practical Applications: There was a strong, positive relationship between muscle size and voluntary strength in our sample. Thus, in this sample, those with larger VLs were able to produce greater torque. However, it is not clear from these data what role increasing muscle size has in increasing strength. Further, there was no relationship between muscle size or maximal voluntary strength and the rate of torque production during a contractile twitch. This may suggest that pRTTD is instead related to factors (e.g., calcium kinetics) other than muscle size and may not influence maximal voluntary strength capabilities.

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Relationship Between Muscle Size and Function.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Effects of Knee Wraps on Immune Cell Mobilization Following Resistance Exercise Designed to Induce Muscle Damage

E. Tagesen,1 J. Laudato,1 B. Gibson,1 C. Dulaney, C. Trionfante,2 and A. Jajtner

1Kent State University; and 2Miami University

Prior studies utilizing knee wraps (KWs) while performing a back squat have demonstrated a mechanical advantage that increases exercise volume and load. Purpose: To determine if knee wraps modify the immune response to resistance exercise. Methods: Nine resistance trained men (22.6 ± 3.6 years; 177.1 ± 5.4 cm; 83.2 ± 17.3 kg) were recruited to participate in either a KW or control (CON) condition. During visit 1, participants performed a 1-repetition max (1-RM) and were required to attain a 1-RM between 1.5x and 3.0x their body weight. Participants then returned to the Exercise Performance and Recovery Lab for visit 2 at least 72 hours later, having fasted at least 10 hours, abstained from caffeine for 16 hours, nicotine and alcohol for at least 24 hours, and exercise for 72 hours. During this visit, participants completed a 5-minute warm up on a cycle ergometer at a self-selected pace before completing 8 sets of 10 repetitions of the squat at 70% of their 1-RM, with 2 minutes rest between sets. Blood samples were obtained prior to exercise (PRE), immediately after (IP), 1-(1H), 24-(24H) and 48-(48H) hours after exercise. Blood was immediately analyzed for total leukocyte count (WBC), as well as the number (#) and ratio (%) of lymphocytes (LY), monocytes (MO), and granulocytes (GR) using an automated hematology analyzer. Differences between conditions were analyzed using a Mann-Whitney U test, while differences across time were assessed with a Friedman's ANOVA, and post-hoc analysis with a Wilcoxon rank sum test. Results: Friedman's ANOVA demonstrated differences (p = 0.005) in the KW group for WBC, with increases observed from PRE (5.74 ± 1.41 × 103·µL−1) to IP (9.73 ± 1.15 × 103·µL−1; p = 0.043), with no differences at 1H (5.41 ± 1.04 × 103·µL−1), 24H (5.17 ± 1.13 × 103·µL−1), or 48H (5.12 ± 1.07 × 103·µL−1). Friedman's ANOVA also indicated differences (p = 0.004) in the KW group for LY%, with increases from PRE (34.7 ± 3.8%) at IP (40.9 ± 4.48%; p = 0.043) and a decrease at 1H (22.6 ± 3.1%; p = 0.043). Friedman's ANOVA revealed differences (p = 0.002) for the KW group in LY#, with an increase (p = 0.043) from PRE (1.96 ± 0.39 ×103·µL−1) at IP (3.97 ± 0.597 ×103·µL−1). Friedman's ANOVA indicated differences (p = 0.015) in the KW group for MO#, with increases (p = 0.043) at IP (0.67 ± 0.17 ×103·µL−1) compared to PRE (0.38 ± 0.102 ×103·µL−1), 1H (0.25 ± 0.12 ×103·µL−1), 24H (0.30 ± 0.11 ×103·µL−1) and 48H (0.32 ± 0.08 ×103·µL−1). Additionally, at IP, MO# were greater in KW (0.67 ± 0.17 × 103·µL−1; p = 0.036) versus CON (0.59 ± 0.13 × 103·µL−1). Friedman's ANOVA demonstrated differences (p = 0.004) in the KW group for GR% with increases (p = 0.043) from PRE (58.1 ± 5.1%) and IP (52.4 ± 5.1%) at 1H (73.2 ± 3.8%). Friedman's ANOVA demonstrated differences (p = 0.003) in the KW group for GR# with increases (p < 0.05) at IP (5.11 ± 0.87 × 103·µL−1) compared to PRE (3.37 ± 1.10 × 103·µL−1), 1H (3.95 ± 0.77 ×103·µL−1), 24H (3.05 ± 0.67 × 103·µL−1) and 48H (2.79 ± 0.60 × 103·µL−1). Conclusion: A significant increase in circulating WBCs suggest KWs may increase the immune response possibly due to increased exercise volume. Additionally, the monocyte response to exercise with KW may be enhanced, especially immediately after exercise. Practical Applications: KWs appear to increase the immune response to resistance exercise, which may increase post-exercise inflammation. Therefore, further research is necessary to determine if the use of KWs is beneficial to the athletes.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Comparison of Lymphocyte Subset Responses to High-Intensity Interval Training, Sprint Interval Training, and Moderate-Intensity Continuous Training

E. Arroyo,1 E. Tagesen,1 T. Hart,2 B. Miller,1 and A. Jajtner

1Kent State University; and 2n/a

Purpose: To compare the effects of high-intensity interval training (HIIT), sprint interval training (SIT), and moderate-intensity continuous training (MCT) on lymphocyte subset populations. Methods: Recreationally active men (n = 3; 21.3 ± 3.5 years; 182.8 ± 6.3 cm; 79.4 ± 8.7; 11.2 ± 5.8 %BF; 44.1 ± 3.2 ml·kg−1·min−1) completed a maximal graded exercise test (Vo2max) and 3 exercise trials (HIIT, SIT, and MCT) in a randomized, counterbalanced fashion on a cycle ergometer. HIIT consisted of fifteen 90-second bouts at 85% Vo2max interspersed with 90-second active recovery periods. SIT consisted of fifteen 20-second bouts at 130% maximum wattage interspersed with 160-second active recovery periods. MCT was a continuous bout at 65% Vo2max. Each trial lasted 53 minutes, including a 5-minute warm-up and a 3-minute cool-down. Blood was collected before (PRE), immediately post (IP), 30 minutes (30P), 2 hours (2H), 6 hours (6H) and 24 hours (24H) post-exercise. The number and percentage of lymphocyte subsets (CD3+CD4+, CD3+CD8+, CD3CD56brightCD16, CD3CD56dimCD16+, and CD3CD19+) were analyzed via flow cytometry. Total lymphocyte count was analyzed via hematology analyzer. Changes were assessed using a 2 factor (time × trial) within-subjects repeated measures ANOVA. Results: A significant time × trial interaction was observed for CD3+CD4+ percentage (F = 2.989, p = 0.018) and count (F = 2.653, p = 0.030). CD3+CD4+ count decreased from PRE to 24H in both MCT (p = 0.007) and SIT (p = 0.030), but not HIIT (p > 0.05). During HIIT, CD3+CD4+ count was increased from PRE to IP (p = 0.008). A significant time × trial interaction was observed for CD3+CD8+ (F = 4.909, p = 0.001) and CD3CD19+ counts (F = 2.536, p = 0.037). CD3+CD8+ count was elevated at 6H compared to 2H in both MCT (p = 0.016) and HIIT (p = 0.032), but not SIT. For HIIT, CD3CD19+ count was greater at IP relative to PRE (p = 0.019), 30P (p = 0.033), and 24H (p = 0.041). A significant time × trial interaction was observed for CD3CD56brightCD16 count (F = 6.010, p < 0.001). At IP, CD3CD56brightCD16 count was greater for HIIT compared to MCT (p = 0.017) and SIT (p = 0.013). A significant time × trial interaction was observed CD3CD56dimCD16+ percentage (F = 4.206, p = 0.003) and count (F = 3.203, p = 0.013). For SIT, CD3CD56dimCD16+ count was lower at 2H compared to PRE (p = 0.047). Conclusion: Data suggest that both SIT and MCT, but not HIIT, elicited a decline in CD3+CD4+ count 24 hours following exercise. HIIT and MCT triggered a significant increase in CD3+CD8+ count at 6H that was not observed following SIT. CD3CD19+ count was elevated at IP following HIIT, but not following SIT or MCT. CD3CD56brightCD16 count was significantly greater immediately after HIIT compared to SIT and MCT. CD3CD56dimCD16+ count declined 2 hours following SIT but not following HIIT or MCT. Practical Applications: The results of this study suggest that, despite identical duration, HIIT, SIT, and MCT elicit dissimilar immune responses. T helper cells (CD3+CD4+), which play an important role in immune function, appear to be suppressed following SIT and MCT, but not HIIT. Cytotoxic NK cells (CD3CD56dimCD16+) were depleted 2 hours following SIT, but not following HIIT or MCT, indicating potential susceptibility to infection following SIT. Further research is needed to determine the practical effects of varying exercise intensities on immune function.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Does Sweat Collection Method Influence Assessment of Electrolyte Concentration?

N. Shea, G. Kang, M. Jones, and M. Millard-Stafford

Georgia Institute of Technology

Sweat rate and electrolyte concentration can widely vary across individuals; thus, these measures may inform practitioners regarding nutritional requirements and acclimatization status of athletes. Purpose: To determine the impact of using different methods for sweat acquisition (by region and modality) on sweat electrolyte concentration. Methods: Thirteen physically-active males (age: 22.4 ± 3.5, height 178.0 ± 6.1 cm, body mass: 69.9 ± 6.6 kg) participated after a standardized dinner and an overnight fast. Sweat was acquired via Tegaderm absorbent patch on the left scapula (SCAP-Patch), left forearm (ARM-Patch), and Opsite dressing/parafilm pouch (Brisson method) on the right scapula (SCAP-Pouch) after ∼1 hour of exercise in the heat (38 °C, 30% RH). Sweat was obtained from the beginning of exercise until patches were visibly saturated and pouch contained sufficient sample volume. Sweat was analyzed for sodium [Na+] and potassium [K+] via LAQUAtwin Na-11 and LAQUAtwin K-11. Results: There was a significant effect for sweat acquisition method on Na+ (p = 0.002) and K+ (p < 0.001). CAP-Pouch had higher [Na+] by 16.9% compared to SCAP-Patch (83.1 ± 25.3 > 71.0 ± 18.2 mmol/L; p = 0.010); however, this regional measure was highly correlated (r = 0.861; p < 0.001) despite a different acquisition technique. A similar finding was observed for [K+]. SCAP-Pouch had higher [K+] by 18.4% compared to SCAP-Patch (4.5 ± 0.6 > 3.8 ± 0.7 mmol/L; p = 0.009) but was significantly correlated (r = 0.815; p = 0.001). Sodium differences across regions were not different for SCAP-Patch and ARM-Patch (71.0 ± 18.3 vs. 61.9 ± 21.6 mmol/L; p = 0.084), but were highly correlated (r = 0.795, p = 0.001). Regional differences were only observed for [K+]. Ard greater [K+] compared to SCAP-Patch 5.4 ± 1.2 > 3.8 ± 0.7 mmol/L; p = 0.002) but was significantly correlated (r = 0.734, p = 0.024). Conclusion: Sweat electrolyte concentration may differ both by region and the acquisition method used in sample collection. The use of absorbent patches resulted in consistently lower electrolyte values for both [Na+] and [K+] compared to a custom-made pouch in the same region (i.e., scapula). Practical Applications: Regional sweat collections within occlusive coverings may result in higher values compared to whole body sweat. However, despite potential differences by region and sample collection, the high correlation among methods indicates a benefit to correctly identify individuals who are at risk for excess sodium loss using these field techniques.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Acute and Long-Term Affects of Mediation on Cortisol Levels in Kinesiology Students

T. Dore' and G. Davis

University of Louisiana at Lafayette

Numerous studies have concluded that regular mediation practice has had a significant effect on cortisol levels. Purpose: To investigate the potential effects of regular meditation on both acute and long-term stress and anxiety levels in University students. Methods: Twelve participants (5 men and 7 women) participated in the study. The subjects were randomly divided into 2 groups, a meditation group (group 1) and a non-meditation group (group 2). Ages of the participants ranged from 18 to 23 year old. All participants provided a pre- and post-cortisol saliva sample between the hours of 0600 and 0800 and completed GAD-7 survey to assess anxiety. On the initial day of testing, group 1 was required to participate in a 10-minute guided mediation session during the time between the cortisol sampling. Over the course of a 15-week semester, the participants in group 1 were required to participate in bi-weekly meditation sessions ranging from 10 to 25 minutes in duration while the participants in group 2 were required to meet bi-weekly for 10–25 minutes and sit quietly. During the week prior to final exams, both groups were again required to participate in the GAD—7 survey and provide an additional saliva sample. Cortisol was analyzed using a commercially available ELISA. Results are presented as mean ± SEM. Results: Cortisol levels for group 1 were 0.10 ± 0.03 µg/dl pre-intervention, 0.07 ± 0.02 µg/dl post-acute intervention, and 0.09 ± 0.03 µg/dl post-15 weeks intervention. Cortisol levels in group 2 were 0.27 ± 0.11 µg/dl, 0.06 ± 0.03 µg/dl post-acute intervention and 0.05 ± 0.02 µg/dl post-15-week intervention. A repeated measures ANOVA did not reveal a significant effect for treatment (F = 0.53; p = 0.49), time (F = 1.10; p = 0.38), or an interaction (F = 0.77; p = 0.50). GAD-7 scores for group 1 were 8.75 ± 1.38 pre-intervention and 7.4 ± 1.86 post-15-week intervention while GAD-7 scores for group 2 were 9.0 ± 2.50 pre-intervention and 6.17 ± 1.80 post-15-week intervention. A repeated measures ANOVA did not reveal a significant effect for treatment (F = 0.28; p = 0.62), time (F = 0.56; p = 0.48), or an interaction (F = 2.76; p = 0.15). Conclusion: Neither an acute bout of meditation nor a fifteen-week bi-weekly meditation intervention was effective in affecting anxiety or salivary cortisol levels in college aged-men and women, likely due to the low initial values of these parameters. Practical Applications: If men and women initially display low levels of stress or anxiety, acute or chronic meditation is unlikely to induce any significant physiological changes associated with decreases in stress or anxiety. Meditation may still provide psychological benefits in this population and physiological benefits may be realized among participants with higher initial stress or anxiety.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

The Acute Cortisol Response to Resistance Exercise: the Importance of Training Status

S. Sontag,1 J. Nicoll,2 A. Fry,1 and E. Mosier3

1University of Kansas; 2California State University, Northridge; and 3Northwest Missouri State University

Purpose: To examine the importance of training status on the acute cortisol response to a lower body high volume-moderate intensity resistance exercise (RE) bout in college aged men. Methods: Resistance trained (RT) men (n = 10; ±SD, age = 21.3 ± 1.7 years, height = 175.8 ± 6.8 cm, body mass = 84.5 ± 13.5 kg, squat 1RM = 154.3 ± 19.3 kg, training history = 5.4 ± 2.0 years) and untrained men (UT) (n = 9; ±SD, age = 20.8 ± 3.1 years, height = 178.7 ± 8.9 cm, body mass = 81.0 ± 14.0 kg, squat 1RM = 108.1 ± 13.7 kg, training history = 0.7 ± 1.7 years) volunteered for this study. Some untrained subjects had prior RE experience but were classified as untrained due to a lack of current training. Prior to the RE bout, subjects came in for a 1RM strength test for the barbell back squat and leg extension according to NSCA guidelines (Baechle and Earle 2008). Subjects returned 4–7 days later euhydrated and at least 6 hours fasted, between 10am and 2pm, and completed a RE bout consisting of 6 sets of 10 repetitions of barbell back squats at 75% 1RM with 1.5 minutes rest between sets, immediately followed by 4 sets of 10 repetitions of leg extensions at 75% 1RM with 1.5 minutes rest between sets. Blood samples were collected via venipuncture from an antecubital vein before the RE bout (PRE) and 5 minutes (5+), 15 minutes (15+), and 45 minutes (45+) post exercise. Circulating serum concentrations of cortisol were analyzed via ELISA. Statistical analyses were completed using 2-way repeated measures ANOVAs. Results: In the RT group, there were significant increases (p < 0.05) from PRE to 5+ and PRE to 15+ post RE bout (See Table 1). In the UT group, there were significant increases (p < 0.05) at 5+, 15+, and 45+ post RE bout (See Table 1). Conclusion: While both RT and UT groups had significant increases in serum cortisol levels following a lower body RE bout, the UT group stayed elevated longer. Practical Applications: Resistance trained and untrained individuals have similar initial responses in cortisol to RE; however, RT individuals are able to return to baseline quicker, indicating a faster recovery. For strength and conditioning professionals, it is important to understand there are differences in the physiological responses of individuals with different training statuses, thus affecting how they adapt and recover.

table3
Table 1.:
Serum cortisol (
± SD; nmol·L−1) ǂ different from PRE (p < 0.05).

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Comparison of Baseline Salivary Testosterone and Cortisol Between National Competitors and Non-qualifiers in Women's Collegiate Track and Field

L. Biscardi, M. Jones, and M. Andre

George Mason University

Testosterone and cortisol are both considered to be valid biomarkers in athletes, and are sometimes monitored to help to assess recovery in athletes (Fry & Kraemer, 1997). Further, scientists have wondered if resting concentrations of these hormones can help to predict talent and/or influence acute performance in athletes (Cardinale & Stone, 2006). Differences in baseline concentrations of salivary free testosterone and cortisol between elite and non-elite women athletes across various sports have been documented. The data suggests that more successful athletes have higher salivary testosterone and cortisol than less successful athletes (Cook et al., 2012 Crewther & Cook, 2018). While these studies have compared athletes at different levels of competition, differences in basal hormone concentrations of women athletes with differing performance success at the same level of competition is of interest. Purpose: To compare salivary free testosterone and cortisol between women NCAA DIII track and field athletes who were national competitors and matched athletes who did not qualify for nationals. Methods: Resting saliva samples were collected from 12 NCAA DIII track and field athletes before a preseason time trial. For analysis, athletes were paired by event to include one athlete who scored points at the NCAA DIII National Championship, and one athlete who went through the same training protocol but did not qualify. Each pair of athletes had the same training schedule with the same coach, and the same competition schedule. Twelve matched pairs (2 throws, 2 sprints, 1 vault, 1 distance) were used for analysis. Independent samples t-tests were used to determine whether or not there was a statistically-significant (p < 0.05) difference between qualifying and non-qualifying athletes for free testosterone and cortisol. Results: National competitors had higher salivary testosterone (mean ± SD: 0.427 ± 0.137 versus 0.250 ± 0.078 nmol/L, p = 0.020) and cortisol (11.54 ± 4.73 versus 5.95 ± 2.14 nmol/L, p = 0.025) concentrations than non-qualifiers, both overall and when matched for event. Conclusion: Baseline testosterone and cortisol measures were higher in national competitors than non-qualifiers. This suggests that the trend observed in elite internationally-competitive women athletes versus non-elite athletes from various sports (including track and field) also occurs between nationally-competitive and non-qualifying NCAA DIII track and field athletes. Practical Applications: These findings support the use of salivary testosterone and cortisol as valid biomarkers in women athletes. It is recommended that practitioners and sport scientists consider monitoring salivary testosterone and cortisol as a tool for differentiating athletic performance potential in addition to recovery assessment. Saliva samples can be collected on a consistent time interval before warming-up for an afternoon practice session, to be included along with other typical monitoring tools, such as surveys, performance tests, and measures of training and competition workload.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Comparison of Various Body Composition Measures Against Criterion 3- and 4-Compartment Models in Collegiate Athletes

S. Lanham, E. Langford, G. Hogan, M. Eisenman, G. Ryan, and R. Snarr

Georgia Southern University

Estimations of anthropometric measures (i.e., body fat percentage [BF%]) are important to consider in athletic populations as variations in body composition may impact health and performance, particularly in power and weight-controlled sports. However, most laboratory and field-based devices estimate BF% using algorithms based upon, and intended for, general populations, which tend to be less physically active. Therefore, these algorithms may not be applicable to special populations (i.e., collegiate athletes), leading to misrepresentation of BF%. Purpose: The purpose of this study was to compare 6 body composition Methods: foot-to-foot bioelectrical impedance analysis (FF_BIA); hand-to-foot bioelectrical impedance analysis (HF_BIA); bioelectrical impedance spectroscopy (BIS); air displacement plethysmography (ADP); dual-energy x-ray absorptiometry (DXA); and a 3-site skinfold test (3SF) against the criterion of both a 3-compartment (3C) and 4-compartment (4C) model in Division-I collegiate athletes. Methods: Sixty-eight athletes (males: n = 38; female: n = 30) from various sports, volunteered for participation in the study. Each participant performed all measures on the same visit to the laboratory, following all standard operating procedures for each test. A repeated measures ANOVA, with Bonferroni pairwise comparisons, was used to determine differences (p ≤ 0.05) within gender between BF% estimation measures compared to the 3 and 4C models. Results: For the male athletes, when compared to 3C (13.9 6.74%) results indicated a significant mean difference with DXA (17.2 ± 9.5%; p < 0.01), BIS (18.8 6.4%; p < 0.01), and HF_BIA (18.9 5.4%; p < 0.01). There were no statistical differences between 3C and ADP (12.4 8.1%; p = 0.24), FF_BIA (11.9 5.9%; p = 0.21), or 3SF (13.5 8.4%; p = 1.0). Similar differences were noted between 4C (12.2 7.1%) and DXA, BIS, and HF_BIA (all p < 0.01). Additionally, no differences existed between ADP (p = 1.0), FF_BIA (p = 1.0), or 3SF (p = 1.0) compared to 4C. For the female athletes, when compared to 3C (22.9 6.6%) results indicated a significant mean difference with DXA (27.7 ± 5.6%) and HF_BIA (26.0 4.3%) (each p < 0.01). There were no significant differences observed between the 3C model and ADP (21.3 ± 5.5%; p = 1.0), BIS (25.2 5.1%; p = 0.60), FF_BIA (22.1 4.6%; p = 1.0), or 3SF (24.1 4.9%; p = 1.0). Similar differences were noted between 4C (22.0 6.8%) and DXA (p < 0.01) and HF_BIA (p < 0.01), with no differences compared to ADP (p = 1.0), BIS (p = 0.11), FF_BIA (p = 1.0), or 3SF (p = 0.92). Interestingly, the 3 and 4C models were significantly different from each other (p < 0.01) in both genders. Conclusion: Results indicated that some laboratory measures (DXA, BIS, HF_BIA) may over predict BF% in athletic populations when compared to more thorough 3 and 4C models. Therefore, consideration on reliance of these tests, as well as the calculating of new algorithms to estimate BF% in athletes may be warranted. Practical Applications: These results suggest that reliance on single laboratory measures of estimating BF% in athletes are likely to result in a misrepresentation of BF%. Additionally, while these results indicated no differences in group means between ADP, FF_BIA, or 3SF compared to 3 and 4C in either gender, practitioners may want to consider incorporating a 3C or 4C model, as these offer a more complete representation of body composition in athletic populations.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Validation of Bioelectrical Impedance Analysis Compared to a Four-Compartment Model Criterion

G. Brewer, M. Blue, K. Hirsch, A. Peterjohn, and A. Smith-Ryan

University of North Carolina at Chapel Hill

Multi-frequency bioelectrical impedance analysis (BIA) technology offers enhanced body composition outcomes including regional estimates (i.e., trunk, limbs) in a relatively short testing period. Research examining the accuracy of stand-up multi-frequency BIA devices compared against a four-compartment (4C) model criterion is limited. Purpose: The purpose of this study was to validate the use of stand-up BIA compared to a 4C model criterion for measurement of body composition including fat mass (FM), fat free mass (FFM), and body fat percentage (%fat) among the total sample and each sex. Methods: Eighty-two healthy male (n = 26) and female (n = 56) normal weight young adults (Mean ± SD; Age: 19.6 ± 1.2 years; Height: 168.5 ± 9.3 cm; Weight: 63.0 ± 8.6 kg; BMI: 22.2 ± 1.8 kg/m2) participated in body composition testing. Body composition was determined using a traditional 4C reference assessment to estimate FM, FFM, and %fat. Body volume was determined from air displacement plethysmography, total body bone mineral content was determined from dual-energy absorptiometry, and total body water was estimated in the supine position from bioelectrical impedance spectroscopy (BIS). Body composition was also determined from stand-up BIA. The 4C body composition variables (FM, FFM, and %fat) were compared against estimates by the single BIA test; validity statistics included total error (TE) and standard error of the estimate (SEE) to examine prediction error between BIA measurement and a 4C model for the same variables. Results: Significant differences were found for FM (p < 0.001), FFM (p < 0.001), and %fat (p < 0.001) values between BIA and 4C model estimates. For the total sample, prediction error was the highest for %fat (TE = 4.2%; SEE = 3.9%) compared to FM (TE = 2.4 kg; SEE = 2.2 kg) and FFM (TE = 2.4 kg; SEE = 2.2 kg). For the male sample, prediction error of %fat (TE = 1.4%; SEE = 2.2%) and FFM (TE = 1.1 kg; SEE = 1.6 kg) were ideal compared to the 4C criterion. Prediction error of FFM was the same as FM (TE = 1.1 kg; SEE = 1.6 kg). For the female sample, prediction error of %fat (TE = 3.9%; SEE = 4.4%) ranged from good to fairly good; prediction errors were very good to excellent for FFM (TE = 2.1 kg; SEE = 2.3 kg). Prediction error for FFM were similar to FM (TE = 2.1 kg; SEE = 2.4 kg). Conclusion: Validation of stand-up BIA technology compared to a 4C model revealed differences for estimates of FM, FFM and %fat. Specifically, the highest error was seen in %fat for the total sample and each sex. All measurements of error were higher in females compared to males. Practical Applications: These results suggest that utilization of stand-up BIA in men may result in a 1.4% overestimation of %fat, 1.0 kg overestimation of FM, and 1.0 kg underestimation of FFM compared to estimation by a 4C model. For females, stand-up BIA may result in a 1.7% overestimation of %fat, 1.0 kg overestimation of FM, and 1.0 kg underestimation of FFM compared to estimation by a 4C model. Estimation for FM and FFM values by stand-up BIA compared to a 4C model demonstrate good agreement, and may be a practical, feasible, and accurate measure of body composition.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Longitudinal Body Composition Changes of NCAA Division-1 Female Gymnasts

A. Buttram,1 R. Herron,2 S. Reddy,1 and J. Casey1

1University of North Georgia; and 2United States Sports Academy

Body size and composition are important anthropometric and physiological components of physical fitness that influence athletic performance and health. However, limited research is available examining longitudinal changes of body composition during preparatory and competitive seasons in female athletes, especially female NCAA gymnasts. Purpose: The intent was to assess longitudinal body composition and anthropometric changes in female NCAA Division-1 gymnasts over the course of 2 preparatory and competitive seasons. Methods: Ten (n = 10) female, NCAA gymnasts (Mean ± SD; Age: 19 ± 1 year, Height: 158.5 ± 5.0 cm) participated in this study. Participants visited the laboratory 7 times over the course of 2 preparatory and competitive seasons. Season one consisted of measurements in August (A1), October (O1), January (J1), March (M1). Season 2 had measurements in September (S2), November (N2), and February (F2). Each visit, body weight (BW), body fat percentage (BF%), fat mass (FM), and fat-free mass (FFM) were measured using air displacement plethysmography (BODPOD). Changes in each variable were analyzed with repeated measures analysis of variance and, as needed, post-hoc Fisher's Least Significant Difference (LSD). Results: Body size and composition values can be found in Table 1. BW significantly increased between A1 and O1 (p = 0.008) but subsequently remained constant thereafter. FFM significantly increased from A1 to O1 (p < 0.001) and from O1 to N2 (p = 0.045). There were no other statistical differences found. Conclusion: This investigation indicated that female Division-1 gymnasts observed an increase in BW during the preparatory season, primarily due to an increase in FFM. Furthermore, FFM increased from the preparatory phase of season one to the preparatory phase of season 2 without a statistically significant change in any other metric. BF% and FM remained unchanged throughout both seasons. Practical Applications: Monitoring longitudinal changes in body composition can be useful for athletes and strength and conditioning specialists. Over the course of multiple seasons, gymnasts can be expected to maintain their FM and BF% while increasing BW and FFM.

F12

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Validity of a Four-Compartment Body Composition Model Utilizing Dual Energy X-Ray Absorptiometry-Derived Body Volume in Normal Weight Individuals

M. Blue, K. Hirsch, A. Peterjohn, G. Brewer, and A. Smith-Ryan

University of North Carolina at Chapel Hill

Multi-compartment models are the gold standard for body composition assessment as they measure multiple constituents of the body. The traditional four-compartment (4C) model requires a minimum of 3 devices to measure body composition, limiting feasibility in athletic populations. A more efficient, modified 4C model that utilizes dual-energy X-ray absorptiometry (DXA) to estimate body volume (BV) has been developed. Thorough validation of the modified 4C method in various populations is required to recommend widespread application. Purpose: To evaluate the validity of DXA-derived BV for use in a 4C body composition model in a normal weight sample. Methods: Body composition of 82 normal weight (Body Mass Index [BMI]: 18.5–24.99 kg/m2) young adults (Mean ± SD; Age: 19.6 ± 1.1 years; BMI: 22.1 ± 1.8 kg/m2, 68.3% female, 80.5% Caucasian) was measured by 2. Methods: a criterion 4C model and a DXA-derived BV 4C model (DXA-4C). For both models, bioelectrical impedance spectroscopy (BIS) was used to estimate total body water and a full body DXA scan was used to measure total body bone mineral content. For the criterion 4C model, BV was measured by air displacement plethysmography. For the DXA-4C model, BV was derived from previously published coefficients and DXA total body fat mass, lean mass and bone mineral content measures. Results: For the DXA-4C model, total error (TE) and standard error of the estimate (SEE) values for BV (TE = 0.77 L; SEE = 0.65 L), %fat (TE = 3.6%; SEE = 3.4%), and fat free mass (FFM; TE = 2.1 kg; SEE = 1.8 kg) represented good to very good agreement with the criterion 4C model. The DXA-derived measures of body composition (BV: 59.3 ± 8.3 L; %fat: 19.4 ± 7.2%; FFM: 50.8 ± 8.7 kg) were significantly different (p < 0.01) than 4C criterion measures (BV: 59.5 ± 8.0 L; %fat: 20.7 ± 8.2%; FFM: 50.1 ± 9.7 kg). Conclusion: Although small statistically significant mean differences were observed between the criterion and the DXA-4C model, the TE and SEE values demonstrate the DXA-derived BV coefficients can be used in a 4C model to accurately measure body composition in normal weight individuals. Future investigations should validate the modified 4C model in individuals with high FFM. Practical Applications: Based on results of the current study, a quick (1–2 minutes) total body water measure by BIS and measures from a total body DXA scan can be combined to accurately predict body composition. For a lean individual (4C criterion %fat = 11.9%), the DXA alone estimated 14.6% whereas the DXA-4C model estimated 11.3%, greatly improving accuracy. Implementing a valid, modified 4C model that requires less time and equipment than a traditional multi-compartment model may enhance body composition assessment in athletics, leading to better strength and conditioning and nutrition recommendations.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Body Composition Analysis of Active Duty Air Force Men and Women

G. Leahy,1 T. Crowder,2 and J. Mayhew3

1Kirtland Air Force Base; 2United States Military Academy; and 3Truman State University

Branches of the military continue to evaluate various means of assessing body composition owing to its relevant contribution to fitness performance tests and functions of duty. Service men and women often undergo routine screening for body composition as a part of performance assessment. Yet to be determined is the best way to determine body composition to provide the best assessment of its effects on physical performance. Purpose: To evaluate body composition differences among age and activity groups in active-duty Air Force personnel. Methods: Men (n = 267) and women (n = 135) volunteered to be evaluated for body composition using air displacement plethysmography to determine fat mass (FM), fat-free mass (FFM), and percent body fat (%fat). Percent fat groups were established in men and women as underfat (<10% and <20%, respectively), average (10–20% and 20–30%, respectively), overfat (20–30% and 31–40%, respectively), and obese (>30% and >40%, respectively). Height and weight were used to calculate BMI (kg/m2), and groups were determined using the standard categories (Underweight ≤18.5, Normal = 18.6 to 24.9, Overweight = 25.0 to 29.9, Obese ≥30). Individuals were stratified for age by decade. Masked obesity was assessed as BMI < 25 when %fat was greater than the overfat level for men (≥20%) and women (≥30%). Results: A 2 × 4 (Sex × Age Group) MANOVA produced a significant interaction effects (p = 0.02) for FFM but not for %fat, FM, or weight. FFM was comparable in men 20–29 years (67.6 ± 8.5 kg) and 30–39 years (66.1 ± 7.6 kg) but significantly lower in 40–49 years (63.6 ± 8.0 kg) and >50 years (62.7 ± 7.3 kg). In women, FFM was less in >50 yr-olds (39.5 ± 3.0 kg) than in the 20-29 yr-olds (46.0 ± 4.8 kg) and 40-49 yr-olds (47.6 ± 4.6 kg) which were less than the 30-39 yr-olds (49.3 ± 6.4 kg). A Chi-square indicated that a significantly greater proportion of men were in the 20–25% (30%) and 25–30% fat groups (40%) than in the >30% group (25%) and <10% group (5%). In women, a chi-square noted significantly more participants in the >30% group (65%) than in 20–25% and 25–30% groups (13 and 17%, respectively) than in the <20% group (5%). BMI group and %fat group identification matched slightly more in men (53%) than in women (47%). FM was positively correlated with age in men (r = 0.27, p < 0.001) but not in women (r = 0.06, p = 0.51), suggesting that men may gain approximately 0.35 kg/y of FM during their service time. BMI had a significantly higher correlation (p < 0.001) with %fat in women (r = 0.80) than in men (r = 0.65). Multiple regression to predict BMI from FM and FFM indicated that FM accounted for 82% of the variance in men while FFM accounted for only 18%. In women, FM accounted for 99% of the variance in BMI, leaving only 1% accounted for by FFM. High BMI values (>30 kg/m2) correctly identified 22% of obese men (>20% fat) and 24% of obese women (>30% fat). Conclusion: Male Air Force personnel tend to gain FM and lose FFM with weight remaining relatively stable across the age span from 20 to 50 years. Women tend to gain weight in the early decades by increasing FFM and maintaining FM. BMI may not be an accurate means of track changes in either sex. Practical Applications: Accurate practical methods of tracking body composition in military personnel remain to be explored.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Body Composition and Fat Free Mass Index in Collegiate Baseball Players

M. Lane1 and R. Bean2

1Eastern Kentucky University; and 2Bean Enterprises

Introduction: Baseball is a sport that requires high levels of skill, power, and speed. More muscular and leaner athletes are typically faster and more powerful. Defining appropriate lean body mass and percent body fat (BF%), relative to the height of an athlete, may improve team and individual goals. Purpose: To identify body composition and lean body mass relative to athlete height in collegiate baseball players. Methods: One hundred and three athletes on collegiate varsity baseball teams (1.83 ± 0.06 m, 89.4 ± 10.2 kg, 20.5 ± 1.3 years, mean ± SD) from multiple NCAA Division 1 institutions were enrolled in this study. Height and weight were recorded prior to body composition, which was measured utilizing a total body Dual-energy X-ray Absorptiometry (DXA) scan. Lean body mass (LBM (kg)) was then entered relative to the height of the athlete to calculate the Fat Free Mass Index (FFMI) of the athlete utilizing standard BMI calculation methodology (kg/m2). Athletes were divided into position groups; infielder, outfielder, pitcher, or catcher based upon their primary role. ANOVA tests were conducted between the groups with least square differences post hoc analysis. Results: Overall BF% was 19.6 ± 6.1, with position values: infielder = 18.8 ± 5.2, outfielder = 18.8 ± 6.2, catcher = 19.5 ± 5.7, and pitchers = 20.0 ± 6.5. Lean body mass (kg) values were 71.5 ± 6.8 with position values: infielders 71.9 ± 5.8, outfielders 72.8 ± 6.0, catchers 71.2 ± 9.5, and pitchers 72 ± 6.6. FFMI values were 21.2 ± 1.8, with position values: infielders 22.1 ± 1.4, outfielders 21.7 ± 1.4, catchers 21.3 ± 1.6, and pitchers 20.9 ± 1.8. There was a significant difference in the FFMI between the position groups with infielders having a significantly greater FFMI than pitchers (p < 0.01). Conclusion: Overall there was a difference in the FFMI between infielders and pitchers. This finding indicates a wide range of differences in athletes and gives a height relative projection of LBM athletes can attain. Further research in to how lean body mass and FFMI changes throughout athletic careers needs to be performed to understand the magnitude of change that is possible.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Muscle Architecture and Quality Differences Among Fitness Competitors and Physically-Active Adults

C. Almeda, G. Mangine, T. VanDusseldorp, Y. Feito, T. Esmat, and M. Stratton

Kennesaw State University

The events in competitions that feature high-intensity functional training (HIFT) are structured to uniquely challenge some combination of the competitors' strength, endurance, and sport-specific skill. The architectural characteristics of skeletal muscle (i.e., muscle thickness [MT], pennation angle [PA], fascicle length [FL], and cross-sectional area [CSA]) are thought to be indicative of strength and power capability. Likewise, muscle quality (MQ) via echo intensity (EI) from ultrasound or the ratio muscular force production and size may also influence these capabilities. However, little is known about muscular architecture and quality differences among HIFT competitors in relation to physically-active adults. Purpose: To examine differences in muscle structure of the upper arm and leg between advanced HIFT competitors (ADV), recreational HIFT competitors (REC), and physically-active adult controls (CON). Methods: Ultrasound assessments in the rectus femoris, vastus medialis, vastus lateralis (VL), biceps brachii (BB), and triceps brachii (TB) to obtain MT, PA, FL, CSA, and EI, along with isometric mid-thigh pull peak force (FRC) were collected in ADV (n = 8; 27.8 ± 4.2 years; 169.8 ± 11.4 cm; 79.8 ± 13.3 kg), REC (n = 8; 33.5 ± 8.1 years; 171.8 ± 13.5 cm; 76.3 ± 19.5 kg) and CON (n = 7; 27.5 ± 6.7 years; 170.7 ± 13.7 cm; 74.5 ± 14.3 kg). MQ was calculated as the ratio between FRC and the sum of CSA in the 3 quadriceps muscles. Participants were considered ADV if they had previously progressed to at least the regional round of the primary international HIFT competition. REC possessed HIFT experience (>2 years) and trained 3–5 days·wk-1 for the last year, while CON possessed resistance training experience (>2 years) but not in HIFT and incorporated resistance and cardiovascular training on 3–5 days·wk-1 for the last year. Results: One-way analysis of variance revealed significant group differences in VL MT (p = 0.022), BB PNG (p = 0.007), TB PNG (p = 0.034), and TB FL (p = 0.015). Tukey's post hoc analysis indicated greater VL MT and BB PA in ADV compared to CON (VL MT: mean difference = 0.54 ± 0.20 cm, p = 0.032; BB PA: mean difference = 5.5 ± 1.60°, p = 0.006) and greater TB PA and shorter TB FL in ADV compared to REC (TB PA: mean difference = 8.38 ± 2.96°, p = 0.027; TB FL: mean difference = 3.71 ± 1.21 cm, p = 0.016). No other significant differences were observed. Conclusion: The architectural differences in this study suggest that advanced HIFT competitors possess larger and potentially stronger musculature (i.e., greater PA and shorter FL) compared to recreational-level competitors and physically-active adults. However, no specific strength or quality differences were observed when considering isometric strength. Practical Applications: Recreational athletes should consider emphasizing the development of the upper-arm musculature and quadriceps to potentially improve their status as HIFT competitors.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Comparison of Multiple Body Composition Measures Against Criterion 3- and 4-Compartment Models in Firefighters

R. Snarr, E. Langford, G. Ryan, and B. Melton

Georgia Southern University

In tactical occupations, such as firefighting, anthropometric measures (i.e., body fat percentage (BF%)) are an important variable due to their strong associations with job performance, as well as general health. While multiple measures of body composition exist, previous literature has demonstrated significant differences between these methods in various populations. However, limited research exists assessing BF% within active firefighters through various measures compared to multi-compartment models. Purpose: The purpose was to compare 7 body composition methods (foot-to-foot bioelectrical impedance analysis (FF_BIA); hand-to-foot bioelectrical impedance analysis (HF_BIA); bioelectrical impedance spectroscopy (BIS); air displacement plethysmography (ADP); dual-energy x-ray absorptiometry (DXA); and 2 3-site skinfold tests (National Fire Protection Association (NFPA) & 3SF)) against the criterion of both a 3-compartment (3C) and 4-compartment (4C) model in firefighters. Methods: Thirty-three firefighters (age = 34.1 ± 8.7 years; height = 178.9 ± 5.9 cm; weight = 93.2 ± 15.2 kg) underwent a test battery consisting of 7 various body composition measures to estimate BF%. The criterion 3 and 4C models were derived from body volume (ADP), total-body water (BIS), body weight (kg), and total bone mineral via DXA (4C model only). A repeated measures analysis of variance (ANOVA) was run to examine any differences between the various methods of determining BF% compared to the 3 and 4C models. Results: Results of this investigation are provided in Table 1. The findings demonstrated a significant omnibus test for the ANOVA (F = 18.5; p < 0.01). Further pairwise comparisons indicated significant mean differences between NFPA, 3SF, and HF_BIA when compared to the 3C model. While significant mean differences existed between the 4C model when compared to both skinfold tests. Additionally, 3SF, NFPA, FF_BIA, and HF_BIA demonstrated unacceptable standard error of the estimates (SEE) as compared to the 4C model (i.e., >4.0%). Conclusion: Results of this study indicate that NFPA and 3SF provided significantly lower BF% values when compared to both multi-compartment models. These differences may represent the distribution of subcutaneous adiposity and lack of visceral tissue measurements when utilizing skinfold techniques in this population. While DXA overestimated BF% no significant differences were observed and contained the smallest standard error of the estimate (SEE). Practical Applications: While results of this study indicated no differences in group means between FF_BIA or HF_BIA compared to 4C, practitioners should take note that large SEE's were observed. When comparing laboratory and field-based measures of body composition to 3 and 4C models, tests such as the 3SF and NFPA may significantly underestimate body fat percentage. Thus, caution is warranted for the overall use of skinfold measurements in firefighters as underestimations may occur.

table4
Table 1.:
Comparison of body fat percentages from various measures against a 3 and 4C criterion.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Comparison and Validation of Bioelectrical Impedance and Air Displacement Plethysmography Against a 3-Compartment Body Composition Measurement Model

K. Hirsch, M. Blue, A. Peterjohn, G. Brewer, and A. Smith-Ryan

University of North Carolina at Chapel Hill

Accurate body composition measurements are important for determining appropriate training and nutrition interventions to maximize performance and minimize injury risk. Air displacement plethysmography (ADP) is a popular method for assessing body composition in athletes and tactical personnel due to reliable measurements and short assessment time. Direct segmental, multi-frequency, tetrapolar bioelectrical impedance spectroscopy (BIS) devices have grown in popularity due to the ability to evaluate total body and segmental (i.e., arm, leg, trunk) composition. However, to date, there is limited information regarding differences in percent body fat (%BF) estimations between these devices and how validity may vary with increasing fat-free mass. Purpose: To compare %BF estimations of BIS, ADP, and a criterion 3-compartment (3C) model. A secondary purpose was to evaluate how fat-free mass index (FFMI) influences prediction error of BIS and ADP. Methods: Percent body fat of 84 young adults (68% Female; Mean ± SD: Age = 19.6 ± 1.2 years; Height = 168.5 ± 9.2 cm; Weight = 63.1 ± 8.5 kg; BMI = 22.2 ± 1.8 kg·) was measured using 3 different Methods: 1) BIS; 2) ADP and; 3) Siri's 3C model, using total body water BIS and body density from ADP. Total error (TE) and standard error of the estimate (SEE) were used to evaluate prediction error compared to the 3C-model for the total group and in individuals with a low (<33 percentile; 15.3 ± 0.7 kg·m−2), moderate (33–66 percentile; 17.3 ± 0.4 kg·m−2), and high (>66 percentile; 19.4 ± 1.4 kg·m−2) FFMI, calculated from the 3C-model. Results: BIS %BF was significantly greater than %BF measured from ADP [Mean difference (MD) ± SD; 1.3 ± 3.5%; p = 0.001], and the criterion 3C-model (1.1 ± 3.9%; p = 0.015); ADP was not significantly different from the 3C-model (−0.2 ± 3.3%; p = 0.535). After outliers were removed (MD ≥ 3SD; BIS n = 2; ADP n = 1), BIS prediction error compared to the 3C-model (TE = 3.3% and SEE = 3.2%) was greater than ADP (TE = 2.8% and SEE = 2.5%). BIS prediction error was lowest in individuals with a low FFMI (TE = 2.3%; SEE = 1.7%) and increased as FFMI increased (Moderate: TE = 3.7% and SEE = 3.0%; High: TE = 5.3% and SEE = 3.8%). This increase in error was less pronounced with ADP (low: TE = 2.9% and SEE = 2.0%; Moderate: TE = 3.1% and SEE = 2.5%; High: TE = 3.8% and SEE = 3.1%). Conclusion: Compared to a 3C-model, BIS tended to over-predict %BF. Although prediction error was considered acceptable for both devices in the full sample, greater error was observed in individuals with a higher FFMI. This was especially true for BIS %BF measurements. Practical Applications: ADP and BIS each provide beneficial information to coaches, trainers, and sport science personnel about their athletes. Although both ADP and BIS can be considered to provide valid body composition measurements, measurements should be interpreted with greater caution when measuring individuals with large amounts of muscle. For example, a collegiate football player might be measured at 20% BF from the 3C-model, but 23.8% from the BIS and 23.1% from the ADP. In comparison, a female cross country runner measured at 20%BF from the 3C-model, might be predicted at 21.7% from the BIS and 22.0% from the ADP.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Position-Specific Body Composition Values in Female Collegiate Rugby Union Athletes

P. Harty,1 H. Zabriskie,1 R. Stecker,1 B. Currier,1 J. Moon,1 S. Richmond,1 A. Jagim,2 and C. Kerksick

1Lindenwood University; and 2Mayo Clinic Health System

Rugby union is a full-contact, intermittent team sport that is rapidly growing in popularity in the United States. Anthropometric characteristics of rugby union athletes have been shown to influence suitability for a given position and affect performance, as forwards are typically larger and more muscular while backs are smaller and leaner. Though several investigations have reported position-specific data in males, little anthropometric data exists in female rugby union athletes. Purpose: To report position-specific body composition values in female collegiate rugby union athletes and identify anthropometric differences between positions. Methods: This investigation was a cross-sectional study involving 101 female collegiate rugby union athletes, categorized as forwards and backs as well as by position (props, hookers, locks, flankers, number 8 forwards, halfback, fly-half, centers, wings, and fullbacks). Anthropometric characteristics of all athletes were measured, and body composition was assessed via dual-energy x-ray absorptiometry one time during a three-year period. Players were classified into forwards and backs and by position using information from team rosters. Outcome variables included weight, height, fat mass, fat-free mass, body mass index, fat mass index, fat-free mass index, bone mineral content, bone mineral area, and bone mineral density. Independent sample t-tests and Mann-Whitney U tests were used to detect differences in outcome variables between forwards and backs, depending on normality of the variable. One-way ANOVAs with Tukey post-hoc tests were performed to identify outcome variables with significant differences between positions. Results: Significant differences (p < 0.014) were identified between forwards and backs for every anthropometric variable (Table 1). Likewise, significant differences (p < 0.01) were identified for every anthropometric variable between several positions. Furthermore, significant (p < 0.05) inter-position differences were identified within the subgroup of forwards but not within the subgroup of backs. Conclusion: Female rugby union forwards and backs differ in all major anthropometric and body composition characteristics, suggesting that larger and more muscular athletes are better suited as forwards, while smaller athletes are better suited as backs. A greater degree of variability in body composition was observed in the group of forwards, while no significant differences were observed in backs. Practical Applications: The present investigation is the first to report position-specific body composition data in female collegiate rugby union athletes. The results of this study can be used by rugby union coaches for recruiting and personnel decisions, to determine a player's suitability for a given position, and to further inform training and nutritional interventions in this population.

table5
Table 1.:
Participant demographics, body composition, and whole-body bone mass in female rugby players by position type.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

The Validity of B-Mode Ultrasound to Assess Body Fat Percentage in Adolescent, Vocational Dancers

A. Chandler,1 D. Sanders,1 A. Moneme,2 A. Walker,2 B. McFadden,3 S. Dona,4 R. Monaco,5 and S. Arent

1Rutgers University; 2IFNH Center for Health and Human Performance, Rutgers University; 3Rutgers Center for Health and Human Performance; 4Tri-County Orthopedics; and 5Atlantic Sports Health

Body fat percentage (%BF) assessment is used to evaluate overall health, nutritional status, and body composition changes over time. Some of the more validated assessment tools, such as air displacement plethysmography (ADP), are not widely accessible due to high costs, while less-expensive field measures (i.e., skinfold calipers) have limited reliability. Ultrasound (US) is proposed as a relatively inexpensive, portable tool for %BF assessment, and results have been shown to correlate with those of validated laboratory methods. However, there are limited data regarding the accuracy of US compared to ADP in adolescent athletes. Previous research found amplitude- (A) mode ultrasound did not accurately predict %BF compared to ADP in gymnasts, but brightness- (B) mode US may be a suitable alternative in similar populations. Purpose: To evaluate the validity of B-mode US compared to ADP to estimate %BF in high-level, adolescent athletes. Methods: Twenty-two adolescent, vocational ballet dancers (Mage = 16.5 ± 1.4; MBMI = 19.4 ± 2.0) participated in this study. Participants arrived for testing euhydrated and 4-hours fasted. %BF was assessed first using ADP and then B-mode US. Subcutaneous adipose tissue (SAT) was measured with US at 7 anatomical sites, pectoralis, subscapula, triceps, midaxillary line, suprailiac, abdomen, and mid-thigh, in order to estimate %BF using a modified Jackson & Pollock formula. The validity of US-estimated %BF was compared to ADP-estimated %BF by calculating the mean, standard deviation (SD), Pearson's correlation, and standard error of estimate (SEE) from linear regression analysis for the total sample and for each sex. Paired sample t-tests were performed to compare mean differences between the 2 methods for the total sample, for the females only (n = 11), and for the males only (n = 11). Statistical significance was set at p < 0.05 for all measures. Results: %BF was strongly correlated between ADP and US across both sexes (r = 0.835, SEE = 2.8, p < 0.001), as well as among each sex separately (females, r = 0.927, SEE = 1.2, p < 0.001; males, r = 0.782, SEE = 1.9, p < 0.001). Total average %BF was 11.53 ± 5.1% from ADP, and 12.3 ± 5.0% from US, with a mean difference of 0.78 ± 2.90% between the techniques. Average female %BF was 14.0 ± 4.5% and 16.3 ± 3.0% from ADP and US, respectively, with a mean difference of −2.3 ± 2.06% between results. Average male %BF was 9.0 ± 4.6% and 8.3 ± 2.9% from ADP and US, respectively, with a mean difference of 0.68 ± 2.93% between techniques. Paired sample t-tests revealed no significant differences between the 2 methods for the entire sample and for males. There was a significant difference in %BF between techniques in females (p < 0.05), despite the presence of a strong correlation. Conclusion: B-mode US can be used to estimate %BF in adolescent, vocational dancers, as results were in agreement with those from ADP. However, more research is needed to evaluate the variations between methods in female athletes. Practical Applications: Practitioners can consider using B-mode US to estimate %BF, as the tools have become more portable and affordable in recent years, making it feasible for field settings. Additionally, unlike ADP, US can provide segmental analysis, allowing regional fat-free mass assessment and tracking, which may be pertinent in young athletes as physical maturation effects body composition.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Comparisons of the Metabolic Intensity at Heart Rate, Ventilatory, and Gas Exchange Thresholds

P. Succi,1 T. Dinyer,1 M. Byrd,1 and H. Bergstrom2

1University of Kentucky; and 2university of Kentucky

Exercise programs for improving cardiorespiratory endurance (CE) are typically prescribed as a percentage of heart rate (HR) or Vo2max (or reserve) at a metabolic intensity that is great enough to stimulate adaptations. The initial relative intensity for exercise prescription may fall within the moderate, heavy, or severe exercise intensity domains, depending on the initial fitness level of the individual. The gas exchange (GET) and ventilatory (VT) thresholds demarcate the moderate from heavy, while the respiratory compensation point (RCP) demarcates the heavy and severe domains. Heart rate based fatigue thresholds may provide useful models for individualized CE prescription. The critical heart rate (CHR) represents the highest HR that can be maintained for an extended period of time without fatigue, and the physical working capacity at the heart rate threshold (PWChrt) represents the velocity where there is no increase in HR. For use in CE exercise programs, it is important to distinguish the initial metabolic intensity for these thresholds (CHR and PWChrt) and determine where they are located relative to the exercise intensity domains (as defined by ventilatory and gas exchange thresholds). Purpose: This study compared the metabolic intensity (Vo2) associated with CHR (CHRVO2) and PWChrt (PWChrtVO2) to the GET, VT, and RCP. Methods: Nine runners (mean ± SD, age 23 ± 3 years, height 174 ± 8 cm, weight 72 ± 13 kg) completed a graded exercise test to exhaustion (GXT) to determine Vo2peak and the velocity at Vo2peak (vVO2peak). The VT, GET, and RCP were determined using the Vslope method from the VE vs Vo2, Vco2 vs Vo2 and VE vs Vco2 plots, respectively. The CHR was determined from the linear regression of the total heart beats vs time to exhaustion (TLim) from 4 treadmill runs to exhaustion at different velocities. The PWChrt was determined from the slope coefficients for the HR vs TLim relationship calculated for the 4, constant velocity runs, and plotted as a function of the corresponding velocities. A one-way repeated measures ANOVA (p ≤ 0.05) with post-hoc Bonferroni corrected pairwise comparisons (p ≤ 0.01) were used to examine differences among the thresholds. Results: The GET and VT were not different (GET = 38.44 ml × kg−1 × min−1, 78% Vo2peak; VT = 37.36 ml × kg−1 × minute−1, 76% Vo2peak; p = 1.000), but both were significantly lower than the RCP (44.70 ml × kg−1 × min−1, 90% Vo2peak; p = 0.010 and p < 0.001, respectively). The CHRVO2 (40.09 ml × kg−1 × min−1, 81% Vo2peak) was not different from the GET (p = 1.000), RCP (p = 0.116), or VT (p = 0.647). The PWChrtVO2 (38.26 ml × kg−1 × minute−1, 77% Vo2peak), however, was significantly lower than the RCP (p = 0.001) but was not different from the GET (p = 1.000) or VT (p = 1.000). Conclusion: These results indicated the initial metabolic intensities at CHRVO2 and PWChrtVO2 lie at the higher and lower ends of the heavy intensity domain, respectively. However, during exercise anchored by a HR, the metabolic intensity may transverse the traditional intensity domains as velocity is reduced to maintain a constant HR. Practical Applications: The PWChrt and CHR are derived from individual performance capabilities and reflect unique metabolic intensities within the heavy domain. The PWChrt (lower end of the heavy domain) may provide a relative intensity more appropriate for untrained populations, while the CHR (higher end of the heavy domain) may be more appropriate for more highly trained populations.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

The Effect of a Familiarization Trial on 20 km Time Trial Performance in Experienced Cyclist

W. Peveler

Liberty University

Purpose: To determine the effects of a familiarization trial on 20 km time trial performance in experienced cyclists. Methods: Twenty-six experienced cyclists participated in this study (Males = 22 and Females = 4). Three different trials were conducted on separate days with at least 48 hours of recovery between trials. The first trial consisted of a graded exercise protocol to determine Vo2max. The last 2 trials consisted of 20 km time trials conducted on a computer controlled stationary trainer using the subject's personal bike. The computer controlled stationary trainer course consisted of a simulated flat 20 km time trial. Means for dependent measures (Performance time) were compared using Paired-Sample T Test and an alpha of 0.05. Times were compared for the total group (n = 26), the upper half (n = 13; Vo2max = 63.17 ± 4.54 ml/kg/min) and the lower half (n = 13; Vo2max = 49.83 ± 5.82 ml/kg/min). The total group was divided into upper and lower halves using Vo2max results from the graded exercise protocol. Results: No significant differences were found between time trial one (35.41 ± 4.07 minutes) and time trial 2 (35.14 ± 3.91 minutes) at p = 0.080 for the total group. There was also no significant differences found between time trial one (33.60 ± 2.32 minutes) and time trial 2 (33.43 ± 2.16 minutes) at p = 0.272 for the upper half. Lastly, there was no significant difference found between time trial one (37.22 ± 4.71 minutes) and time trial 2 (36.83 ± 4.58 minutes) at p = 0.177 for the lower half. Conclusion: Results from this study indicate that there were no significant differences between the familiarization time trial and the second time trial. When the subjects were split into upper and lower halves, based on Vo2max, there were no significant differences in finishing times. Previous research supports that pacing is based off prior racing experience and known race distance. The cyclists' time trial race experience may have offset the learning curve that requires a familiarization trial. Previous research also supports that cyclists perform more optimally in the cycling position in which they most train. The use of the cyclist's personal bike on the computer controlled stationary trainer may have also influenced time trial performance, as they were not required to adapt to a new cycling position. Practical Applications: This study demonstrates that there may not be a need for a familiarization trial when conducting cycling time trail research involving experienced cyclists using their personal bikes.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Daily Heart Rate Variability Among College Football Players Throughout Preseason Camp in The Heat

A. Flatt, J. Allen, C. Keith, and M. Esco

Georgia Southern University

Heat stress and high training loads during preseason camp may serve as a potent stimulus for improving fitness and thermophysiological adaptations that can reduce resting heart rate (HR) and increase HR variability (HRV) in football players. Alternatively, the intense physical demands of training may overtax the athletes, resulting in converse HR and HRV responses. Purpose: To monitor daily HR and HRV in college football players throughout 13 days of preseason camp in hot and humid conditions. Methods: Division-1 players were categorized as linemen (n = 10, height = 191.6 ± 4.7 cm, weight = 131.2 ± 12 kg) and non-linemen (n = 18, height = 187.4 ± 4.4 cm, weight = 96.2 ± 9.4 kg). HR and the natural logarithm of the root mean square of successive differences (LnRMSSD) were acquired 60–90 minutes before training via finger-pulse plethysmography. A questionnaire regarding perceived sleep, fatigue, soreness, stress and mood was administered daily and averaged intra-individually for a single wellness rating (LnWellness). Day 11 was reserved for passive rest. Linear mixed models and effect sizes (ES) ± 90% confidence intervals were used to assess changes in outcome variables. Results: A main effect for day was observed for LnWellness (p < 0.0001). As a group (n = 28) LnWellness on day 1 was greater than days 3, 6–9 and 13 (p < 0.0001–0.039, ES = 0.38 ± 0.45–0.62 ± 0.45). Main effects for position and day (p < 0.001) were observed for RHR. RHR for non-lineman was lower than lineman (66.4 ± 7.2 vs. 73.8 ± 8.6 b·min−1, p = 0.002, ES = −0.93 ± 0.68). As a group (n = 28), RHR on day 12 was lower than days 1–3, 9 and 10 (p < 0.001–0.038, ES = −0.40 ± 0.41–1.05 ± 0.47). Additionally, RHR on day 1 and 2 was higher than days 4, 7, 8 and 13 (p < 0.001–0.048, ES = 0.66 ± 0.45–0.77 ± 0.46). A position × day interaction was observed for LnRMSSD (p = 0.036). LnRMSSD on day 12 was greater than days 2–5, 8, 9 and 10 for linemen (p = 0.0001–0.042, ES = 0.76 ± 0.76–1.41 ± 0.82). Between-groups, LnRMSSD on day 2 for lineman was lower than days 7 and 12 for non-linemen (p = 0.007–0.027, ES = −1.35 ± 0.71–1.73 ± 0.76). Mean ± standard deviation for HR, LnRMSSD and LnWellness are displayed in Figure 1. Conclusion: Despite some reductions in subjective wellbeing throughout camp, HR parameters demonstrated responses consistent with heat acclimation. Non-linemen exhibited favorable changes in HR and HRV earlier than non-linemen. For both groups, peak increases and decreases in HRV and HR, respectively, were observed on Day 12 following a day of rest. Practical Applications: Linemen should be monitored closely within the first few days to ensure that decrements in HRV are not sustained throughout camp. While the observed changes in HR and HRV were considered a positive adaptation to training in the heat, practitioners should be aware that heat acclimation responses may attenuate typical fatigue-related decrements in HR-derived parameters.

F15
Figure 1.:
Mean ± standard deviation for HR-derived parameters and LnWellness. * = Greater than days 2–5, 8, 9 and 10 for linemen (within subjects). ¥ = Lower than non-lineman on days 7 and 12 (between subjects).

Thursday, July 11, 2019, 12:00 pm–1:30 pm

The Effect of Increases and Decreases in Summer Training Volume on Ventilatory Thresholds and Vo2max in NCAA Division III Cross Country Runners

H. Hsu, C. Rodeheffer, and B. Arledge

Wittenberg University

Purpose: Summer serves as the active rest and the preparatory phase for the upcoming season in National Collegiate Athletic Association (NCAA) Division III cross country runners. The purpose of this study was to investigate the effect of summer training volume on Vo2max and ventilatory threshold (VT) in NCAA Division III cross country runners. Methods: Ten NCAA Division III cross country runners (n = 10, 7 males and 3 females, age: 20.3 ± 1.3 years) were assigned into either high volume (HV) or low volume (LV) groups for a duration of 12 weeks. The high and low volume programs were compared to the individual end spring season training volume (HV group: 38.0 ± 10.4 miles/week, LV group: 20.0 ± 7.1 miles/week). The HV group started at a 10% lower training volume (34.2 ± 9.3 to 45.6 ± 12.4 miles/week) in week 1 and increased to 20% higher training volume (34.2 ± 9.3 to 45.6 ± 12.4 miles/week) by week 12. The LV groups progressed from a 30% lower training volume (14.0 ± 4.9 miles/week) in week 1–20% lower training volume (16.0 ± 5.7 miles/week) by week 12. The weekly training volume was evenly distributed over 7 days each week. Each subject received weekly training updates from the researcher. Each subject performed Vo2max tests on a treadmill using an individualized protocol 2 weeks prior to the training regimen and 2 weeks following the regimen. During each test, the gas exchange was collected using a metabolic cart. VT 1 and VT 2 were determined by the comparison among the volume of O2 consumption, the volume of CO2 production, and ventilation. Heart rate (HR) was recorded at rest and during Vo2max tests. Results: After 12 weeks of training, 1) significant greater VT2 and Vo2max in HV group than LV group, which were not observed before training, and 2) a significant increase in VT2 and a significantly decrease in maximum HR (HRmax) than pre training values in HV group, but not in LV group (See Table below). Conclusion: A 12-week summer training program which progressed to a 20% higher training volume than the previous season ending volume resulted in significant improvements in VT 2 and Vo2max, while no significant change was observed in LV group. Practical Applications: The results of this study suggest that, in summer preparatory phase, a HV training program can promote the baseline cardiovascular fitness level for the upcoming season in NCAA Division III cross country runners. LV training programs could be a choice for those who may need to reduce the training volume while still wanting to maintain their cardiovascular fitness level.

table6
Table 1.:
VT1, VT2 and Vo 2max before and after training.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

The Effects of High Intensity Interval Resistance Training on Negative Plasma Volume Shift and Oxygen Consumption in Well-Trained Males

G. Davis, G. Sims, E. Hebert, and R. Kraemer

Southeastern Louisiana University

Plasma volume shift (ΔPV) is a major physiological process that occurs in response to different forms of exercise. Although much research has been conducted on exercise-induced PV shifts, further investigations are needed to determine the effects of high intensity interval training using resistance-based exercise on −ΔPV. Purpose: The present study examined the cardiorespiratory effects of high intensity resistance interval training (HIRIT) using a Tabata protocol on −ΔPV. Methods: 8 healthy males that were well trained in mixed modal exercise (Mean ± SD; Age: 31 ± 12.3 years (20–60); Height: 69.1 ± 12.12 in; BMI: 27.8 ± 3.53; Weight: 183.3 ± 31.5 lbs.) participated in the study. On separate days subjects completed a preliminary trial and an experimental trial. The preliminary trial included measurement of a 12-RM dumbbell thruster max as well as Vo2max using a graded exercise treadmill test for baseline measures of strength, and cardiorespiratory fitness. In the subsequent experimental trial, subjects completed an eight-round Tabata protocol with dumbbells at 50% of their previously established 12RM that included 20 s of work with 10 s rest (1:2 work/rest ratio). Vo2 across time was monitored. Pre- and immediately post-exercise blood samples were collected via venipuncture and heart rate was measured via palpation. Blood samples were analyzed for hemoglobin (Hb) using a hemoglobin analyzer (Hemocue Hb 201+, Hemocue America, Brea, CA), and for hematocrit (HCT) using a microcapillary method. The Dill and Costill method was used to obtain the shift in PV (Dill & Costill 1974). Results: Paired samples t-tests revealed significant—Δ in PV; [M ± SD; PVBefore = 55.89 ± 2.63%, PVAfter = 47.74 ± 3.23% (p = 0.000)] refer to (Fig 1). Mean % Δ in PV was −14.45 ± 5.69%. Repeated measures ANOVA confirmed significant increases in Vo2, (p < 0.01). Exercise Vo2 rose steadily for the first 3 minutes then leveled off. A significantly strong negative correlation was identified between Δ PVAfter and Vo2 (r = −0.74, p < 0.05). No significant correlation was found between Δ in PV and VE or RER across time. Conclusion: One 4-minute bout of thruster (HIRIT) using a resistance based Tabata protocol elicited significant—Δ in pre-PVBefore to post-PVAfter while Vo2 increased during the exercise bout across time. Practical Applications: Results from this study support that resistance-based interval training can elicit a potent cardiorespiratory response in only 4 minutes. This type of protocol has broad applications in not only keeping athletes in prime physical condition, but could serve as a novel way to increase cardiorespiratory fitness in the general population without excessive volume.

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Figure 1.:
Plasma Volume PVbefore and PVafter (%).

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Brain Activity and Skeletal Muscle Oxygenation During a Time to Exhaustion (TTE) on a Cycle Ergometer

R. Dykstra, M. Rincher, S. Robles-Soriano, M. Miller, and N. Hanson

Western Michigan University

Introduction: Electroencephalography (EEG), a non-invasive technique that records and analyzes electrical activity generated in the brain through electrodes on the scalp's surface, has made it possible to capture changes in cortical brain activity during various exercise protocols. Recent evidence has suggested that brain activity increases throughout an incremental exercise test. However, there is insufficient research exploring changes in cortical brain activity during a submaximal time to exhaustion (TTE). In addition, it is unknown how much skeletal muscle oxygenation (SmO2) changes during a TTE. Purpose: To investigate the changes in cortical brain activity and SmO2 during a TTE. Methods: This study included 27 healthy, recreationally active individuals (age range 18–35 years, 15 males). Subjects came to the lab for 2 visits where they completed a graded exercise test (GXT) and a TTE test on an electromagnetically braked cycle ergometer. The GXT was performed to calculate the workload corresponding to 75% of the participants' Vo2max. The TTE was performed at the predetermined workload until exhaustion, which was defined as the time in which the pedal rate dropped below 60 rpm for more than 5 consecutive seconds. A MOXY sensor, which uses near-infrared spectroscopy to measure SmO2, was placed on quadriceps of the dominant leg. A nine-channel, pre-assembled EEG sensor strip, positioned using the international 10–20 system, was used to detect alpha (8–13 Hz) and beta (13–30 Hz) activity throughout exercise. Power spectral density (PSD) for both alpha and beta bands in the dorsolateral prefrontal cortex (DLPFC) was calculated. One-way repeated-measures ANOVAs were used to determine the effect of time on the dependent variables. Due to the open-ended nature of TTE, tests were separated into 5 segments based on the percentage of the test completed (20, 40, 60, 80 and 100%). Results: There was a significant main effect of time for all variables (all p < 0.05). SmO2 decreased from 61.7 ± 15.2% to 50.0 ± 20.3%. For the EEG data, there were significant increases in both alpha and beta power moving from 20 to 40% (3.5 ± 0.3 to 3.9 ± 0.5 mv2/Hz; 3.2 ± 0.3 to 3.5 ± 0.4 mv2/Hz, respectively) of the test completion (p < 0.01). There were no significant changes moving from 40% to the end of the test. Conclusion: Additionally, increases in cortical brain activity in the DLPFC only occurred during the first 40% of the test. An increase in brain activity could denote that greater levels of cortical activation are necessary in the initial stages of a TTE while the subject is becoming accustomed to the workload. Additionally, although the workload was kept constant throughout the test, SmO2 gradually decreased. Practical Applications: This study shows how the brain and skeletal muscle respond to an open-ended test at a constant workload. Transcranial direct current stimulation (tDCS), a non-invasive technique that uses a weak electrical current to increase excitability in underlying neurons in a stimulated area, has been shown to increase the duration of a TTE test. Future studies should consider using tDCS in conjunction with EEG to see what differences exist in cortical brain activity, if any, when augmenting performance.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

The Relationships Between Critical Speed, Respiratory Compensation Point, Ventilation Threshold, and Gas Exchange Threshold

K. Capello, J. Tappero, R. Pettitt, and J. Dexheimer

Azusa Pacific University

Introduction: Exercise intensity is separated into 3 distinct domains: moderate, heavy and severe. Indicators such as critical power or speed (CP/CS), respiratory compensation point (RCP), ventilatory threshold (VT), and gas exchange threshold (GET) may demarcate these exercise intensity domains. CP may coincide with RCP to demarcate between the heavy and severe domains whereas VT and GET occur at similar intensities demarcating the moderate and heavy domains. No previous studies have compared CS from the 3-minute all-out-test (3 MT) to RCP. Purpose: To compare CS from the 3 MT to running speeds at gas exchange thresholds that have previously been used to demarcate exercise intensity domains including VT, GET and RCP. Methods: Twenty-six functionally trained participants (20 males, age: 27.55 ± 4.64, weight: 85.22 ± 12.38 kg, height: 70.98 ± 7.42 in; 6 females, age: 26.17 ± 2.48, weight: 66.19 ± 6.63 kg, height: 65.58 ± 2.14 in) completed a graded exercise test (GXT) and a 3 MT to determine CS, Vo2max, VT, GET and RCP. Participants completed an initial customized GXT ramp test followed by a square wave supramaximal verification phase at 105% peak speed of the initial ramp test. For the 3 MT, participants ran as fast as possible for 3 minutes and 5 seconds on a flat track while an GPS app tracked distance and time. CS was measured using the average velocity of the last 30 seconds of the 3 MT. GET was determined by the inflection in the VCO2-VO2 versus Vo2 curve. VT and RCP were found using the ventilatory equivalent method in which VT was distinguished as the point of increase in the VE/Vo2 versus Vo2 curve where VE/Vco2 remained constant or decreased and RCP was determined as the point where the VE/Vco2 versus Vo2 curve increased. Speed values from the ramp test were then plotted against Vo2 values and the regression equation derived was used to determine speed at VT, GET, and RCP. Speed, %Vo2max and speed as %Vo2max peak speed at all 4 thresholds (CS, RCP, VT, and GET) was analyzed using a one-way repeated measures analyses of variance (ANOVA). Relative consistency between thresholds was evaluated using intraclass correlation coefficients (ICC) whereas absolute consistency was evaluated using coefficient of variation (CV%) and typical error. Significant differences were assessed using a Bonferonni post hoc analysis with an adjusted alpha level (0.05/6) of 0.008. Results: No significant differences were observed between speed for CS (3.50 ± 0.57 m/s) and RCP (3.52 ± 0.47 m/s) (ICC = 0.74; CV% = 7.64%; typical error = 0.27 m/s; p > 0.05) nor speed for GET (2.85 ± 0.36 m/s) and VT (2.85 ± 0.35 m/s) (ICC = 0.98; CV% = 1.73%; typical error = 0.05 m/s; p > 0.05). The speeds associated with the GET and VT, however, were significantly less than CS and the speed associated with the RCP (p < 0.001). Conclusion: The data displayed high ICC between the speed amongst all 4 variables but that CS and RCP were at significantly higher speeds than VT and GET. Practical Applications: There may be a common physiological mechanism of fatigue for CS and RCP and a separate mechanism between GET and VT. These findings support that CS may demarcate between the heavy and severe exercise intensity domains. Using these thresholds, athletes may be able to train at or above these thresholds to elicit positive exercise adaptations.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Aerobic and Anaerobic Differences Among Fitness Competitors and Physically-Active Adults

A. Franklin, Y. Feito, T. VanDusseldorp, T. Esmat, M. Stratton, and G. Mangine

Kennesaw State University

High intensity functional training (HIFT) is thought to be an effective method for improving general physical preparedness. Although daily workouts vary in design, they often include common aerobic training modalities (e.g., cycling, rowing, running) and circuit training, which are known to improve aerobic and anaerobic capacity. However, it is unclear whether advanced (ADV) HIFT participants possess greater capacities than recreational (REC) participants, or how they might compare to individuals who follow more traditional programming schemes. Purpose: To examine aerobic and anaerobic performance differences between ADV, REC, and physically-active controls (CON). Methods: ADV (n = 9, 27.5 ± 4.0 years, 170 ± 11 cm, 79.8 ± 13.3 kg), REC (n = 8, 33.5 ± 8.1 years, 172 ± 14 cm, 76.3 ± 19.5 kg), and CON (n = 7, 27.5 ± 6.7 years, 171 ± 14 cm, 74.5 ± 14.3 kg) reported to the human performance laboratory on 2 occasions separated by approximately 7 days. Participants were considered ADV if they had previously progressed to the regional level of the primary, annual HIFT competition, while REC possessed HIFT experience (>2 years) and trained on 3–5 days per week for the last year. CON did not possess HIFT experience and incorporated both resistance and cardiovascular training on 3–5 days per week of the last year. On their first visit, peak aerobic capacity (Vo2peak, ml·kg−1·min−1) was assessed in all participants on a cycle ergometer. On their second visit, all participants completed a 3-minute maximal effort on the cycle ergometer with resistance set halfway between power achieved at Vo2peak and the gas-exchange threshold (GET). Group comparisons for normally-distributed variables were made using one-way analyses of variance, while all other variables were assessed via Kruskall-Wallis tests. Results: Significant group differences (p < 0.05) were observed for Vo2peak, GET, and critical power (CP) obtained during the bike sprint. ADV possessed greater Vo2peak (50.3 ± 8.5 ml·kg−1·min−1) and GET (30.3 ± 4.6 ml·kg−1·min−1) compared to REC (Vo2peak: 42.4 ± 2.8 ml·kg−1·min−1, p = 0.021; GET: 25.8 ± 2 ml·kg−1·min−1, p = 0.021). Vo2peak was also greater (p = 0.040) in ADV compared to CON (42.3 ± 3.2 ml·kg−1·min−1) while a trend for greater GET (26.7 ± 5.2 ml·kg−1·min−1, p = 0.054) was noted. No differences were found when GET was expressed as a percentage of Vo2peak. CP was greater in ADV (278 ± 41 W) compared to CON (206 ± 38 W, p = 0.033) and tended to be greater than REC (223 ± 73 W, p = 0.088). No other differences were observed. Conclusion: Advanced HIFT participants appear to possess a greater Vo2peak and predominantly greater GET and CP compared to recreational HIFT participants and physically-active adults. Interestingly, the percentage of Vo2peak where GET occurs does not appear to distinguish between these individuals. Additionally, aerobic and anaerobic capacity appear to be similar between individuals who recreationally incorporate HIFT on 3–5 days per week compared to those who utilize more traditional resistance and cardiovascular training. Practical Applications: Aerobic ability, particularly at peak and around the GET, appear to be important training targets for recreational HIFT participants who wish to elevate their competitive status. In contrast, recreationally participating in HIFT or traditional resistance and cardiovascular training appears to elicit similar aerobic and anaerobic benefits.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Determination of Validity for Critical Power of Three-Minute All-Out Test in Hot Environment

Y. Kuo,1 C. Cheng,1 Y. Kuo,2 Y. Lin,1 and S. Ting1

1National Taiwan Normal University; and 2National Taipei University of Nursing and Health Sciences

The 3-min all-out test (3 MT) has been well developed to predict the critical power in thermoneutral temperature (NT) condition. The end power (EP) estimated by 3 MT highly correlates with critical power and second ventilatory threshold (VT2) in NT condition. However, most of athletes usually train under heat stress during their routine training seasons. It is unclear if the EP could discriminate between heavy and severe exercise intensity domains in heat environment (HT). Purpose: This study investigated the effects of heat stress on the validity of 3 MT. Methods: Twelve male cyclists (age 26.1 ± 5.4 years; height 1.74 ± 0.06 m; weight 67.5 ± 8.7 kg) were recruited in a randomized crossover design study. Each subject was required to perform 2 incremental exercise tests (IET) and two 3 MTs in both HT (33° C) and NT (22° C) environments. Physiological responses, such as maximal oxygen uptake (Vo2max), first ventilatory threshold (VT1) and VT2 against the power output (wVO2max, wVT1, and wVT2) were measured during the IET. EP and work-done-above EP (WEP) were recorded during the 3 MT. Results: Significant correlation was observed between wVT2 and EP under NT conditions (NT, r = 0.674, p < 0.05). Similarly, we also found significantly correlation between wVT2 and EP under HT conditions (HT, r = 0.672, p < 0.05). For each condition, power outputs differed significantly across wVT1, wVT2, wVO2max, and EP, being significantly higher at wVO2max than at wVT1, wVT2 and EP, and significantly higher at wVT2 and EP than at wVT1. In addition, no significant difference was found between wVT2 and EP regardless of conditions. Vo2max under HT was significantly higher than that under NT (p < 0.05). However, wVO2max, wVT1, and wVT2 were significantly higher under NT than those in HT (p < 0.05). During the 3 MT, exercise performance (NT vs. HT: EP, 228 ± 34 vs. 219 ± 33 W; peak power, 606 ± 82 vs. 588 ± 87 W; mean power, 308 ± 32 vs. 300 ± 34 W) was significantly higher under NT than HT (p < 0.05), with the exception of WEP. Conclusion: The 3 MT allows valid measurement of EP for well-trained cyclists, even in heat environment. Although the increased physiological stress resulted from HT might impair exercise performance, the EP derived from 3 MT can accurately estimate aerobic capacity under HT condition. Practical Applications: This investigation suggests that the demarcation of exercise-intensity domains can be used to prescribe training programs, to evaluate training adaptations, and to predict performance. Our findings indicate that EP derived from 3 MT in HT condition can distinguish the high and severe exercise intensity domains, in a manner similar to that of VT2 under HT condition. Coaches and athletes must taking the temperature effects into consideration, which is keeping consistent temperature during EP assessment and application.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Predicting Aerobic Capacity and Rowing Performance From the 3 Minute All-Out Critical Power Test

D. Boffey,1 I. Harat, N. Clark,1 C. Herring,1 E. Goldstein,2 M. Redd, and D. Fukuda

1University of Central Florida; and 2University of Central Florida

Success in the sport of rowing is highly related to maximal aerobic capacity, as measured by Vo2max. A 3-minute all-out test (3 MT) has been validated to calculate critical power (CP), which is also highly correlated to Vo2max and performance in the 2,000 m rowing event. While measuring Vo2max requires expensive gas analysis equipment and is generally limited to one athlete at a time, the 3 MT requires only an ergometer for each athlete and enables simultaneous testing of many athletes. Purpose: The purpose of this study was to create prediction equations for Vo2max and 2,000 m time from the results of the 3 MT and body composition testing. Methods: 39 NCAA D1 female rowers (mean ± SD: age 20 ± 1.4 years; height 1.72 ± 0.05 m; weight 76.4 ± 9.8 kg) completed a 3 MT and a Vo2max test on different days during their preseason training camp. All performance tests were performed on a rowing ergometer (Concept II, model D). During the Vo2max test, a portable gas analyzer (Cosmed K5) was used to monitor and record gas exchange and was attached to an upper body harness, minimizing interference with technique. Body composition was measured via bioelectrical impedance analysis (InBody 770). 2,000 m times were provided by the coaching staff. Multiple linear regression was used to derive prediction equations for 2000m time and Vo2max using CP and W′ from the 3 MT. Stepwise multiple regression was used to derive prediction equations for 2000m time and Vo2max from anthropometric (height, weight (BW), body fat percentage) and all 3 MT data (CP, Wʹ, average power (AVGP), peak power, total distance). All statistical analyses were performed using JASP software (9.0.1) and significance was set at an alpha level of p ≤ 0.05. Results: Multiple linear regression revealed that both CP and W′ were significant predictors (p < 0.001, p < 0.01, respectively) and produced the following equation: 2,000 m time = 614.32–0.64CP −0.33 W′ (SEE = 8.21 s; adjusted R2 = 0.86, F = 104.5, p < 0.001). Stepwise multiple regression produced the following equation when all variables were considered: 2,000 m time (s) = 1,319.17 -.1.294 Distance + .81 AVGP - 0.61 Relative Vo2max (SEE = 7.04 s; adjusted R2 = 0.89, F = 93.23, p < 0.001). Distance as the sole predictor had an adjusted R2 of 0.86, adding AVGP increased R2 by 0.024, and adding relative Vo2max further increased R2 by 0.02. There were no correlations between relative Vo2max and 3 MT results. For absolute Vo2max, multiple linear regression revealed that W′ was not a significant predictor and thus was not included in the following model: absolute Vo2max (L/min) = 1.435 + 0.009 CP (SEE = 0.32 L/min; adjusted R2 = 0.47, F = 29.7, p < 0.001). Stepwise multiple regression including all variables produced the following equation: absolute Vo2max (L/min) = 3.24 + 0.007 Distance + 0.013 BW (SEE = 0.29 L/min; adjusted R2 = 0.56, F = 22.00, p < 0.001). Distance as the sole predictor had an adjusted R2 of 0.51 and adding BW increased R2 by 0.06. Conclusion: CP and W′ derived from a 3 MT appear to be highly related to 2000m rowing performance. Using other variables from the 3 MT (distance traveled, AVGP) and including relative Vo2max created the strongest prediction model for 2,000 m time. CP and distance from the 3 MT also exhibited very large relationships with absolute Vo2max. Practical Applications: This study provides evidence for the 3 MT as a potential practical alternative to gas exchange analysis for a rapid estimation of rowers' aerobic capacity and 2000m performance.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

NAIA Athletic Director Opinions Regarding Certification when Working With Student-Athletes in Strength and Conditioning

K. Ryan and S. Stevelinck

Peru State College

Strength and conditioning coaches facilitate student-athlete performance as well as decrease injuries. Requiring proper certifications for strength and conditioning coaches within National Association of Intercollegiate Athletics (NAIA), may further future success for their sports programs. Purpose: To determine the education and qualifications of those fulfilling the role of strength and conditioning coach within the NAIA and to determine what support exists among NAIA Athletic Directors for requiring a certification for those performing said strength and conditioning duties. Methods: Survey questions were distributed to all NAIA Athletic Directors inquiring as to the following: 1) At your institution, who designs the strength and conditioning programs? 2) What is the highest degree obtained by the head strength and conditioning coach? 3) What certification does your head strength and conditioning coach have? 4) The NCAA has adopted legislation requiring that coaches responsible for the design and implementation of strength and conditioning programs obtain some type of certification. Would you be supportive of similar legislation being adopted by the NAIA? If yes, why? If no, why not? Results: Of all respondents (n = 137), 70.07% of athletic directors claimed that they have no strength and conditioning coach and rely upon individual teams and coaches to design their own strength and conditioning programs. Of the athletic directors who said they have a strength and conditioning coach responsible for designing and implementing programs (18.25% respectively), some stated that some sport teams are responsible for the design and implementation of their own strength and conditioning programs (11.68% respectively). Of those that responded to the question pertaining to the highest degree obtained (n = 39), 66.67% stated their coach had a Master's degree and 23.08% responded their coach had a Bachelor's degree. Of those responding to the question inquiring as to what certification was held by their strength coach (n = 39), 84.62% responded with National Strength and Conditioning Association (NSCA) Certified Strength & Conditioning Specialist (CSCS), 33.33% responded NSCA Certified Personal Trainer (CPT), 25.64% responded USA Weightlifting Sport Performance Coach (SPC), and 17.95% responded with Strength and Conditioning Coach Certified (SCCC)/Master Strength and Conditioning Coach (MSCC) -Collegiate Strength and Conditioning Coaches Association (CSCCa). Lastly, when asked if they were supporting of legislation requiring a certification, 64.66% of 133 respondents said yes with the safety of the collegiate student-athlete being the primary reason why. Of those responding no (35.34%), cost was the primary factor. Conclusion: An overwhelming percentage of athletic departments within the NAIA have no designated strength and conditioning coach and instead rely upon individual teams and coaches to design the strength and conditioning programs for their respective teams. Despite this, the majority of NAIA Athletic Directors favor adopting legislation requiring a certification among those designing and implementing a strength and conditioning program for student-athletes, citing safety as the primary reason. Of those responding no, cost was the deciding factor. Practical Applications: It would appear that the NSCA has the potential for an increase in the number of certified practitioners within the NAIA if able to reduce the cost of certification.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Trends in Strength and Conditioning Discourses That Inform Coaching Practices

C. Kuklick,1 B. Gearity,2 J. Maldonado,3 and S. Maloney3

1Master of Arts in Sport Coaching/Graduate School of Professional Psychology/University of Denver; 2University of Denver; and 3University of Denver; Master of Arts in Sport Coaching

Dominant (i.e., normal, prevalent) discourses in strength and conditioning (S&C) are drawn from biophysical sciences and become enacted by coaches through disciplinary practices (i.e., control of time, space, and flow of bodies) in an attempt increase athletic performance, however, sociologist of sport have repeatedly shown how this also results in unintended, negative consequences (e.g., athlete underperformance, psychological distress Denison, 2010). No research has examined the pervasiveness of social media as a powerful medium to convey dominant discourses and S&C practices, which is essential to understanding how millions of people, including coaches, take in information on platforms including YouTube. Purpose: We drew upon the sociology of sport research to address 2 main purposes: 1) Map trends in S&C discourses used in YouTube videos; 2) Examine how S&C discourses inform coaching, including disciplinary, practices used by S&C coaches. Methods: We engaged a rigorous qualitative analysis of 87 YouTube videos of NFL and NCAA Division I S&C coaches from 2009 to 2019. Videos were transcribed verbatim, then coded while viewing the videos, then units were grouped into theoretically informed themes that represent the dominant discourses and the coaches' use of disciplinary practices. Findings: Dominant discourses were associated with the coaches' use of power and desired outcomes for S&C training, including: strength/power, hypertrophy, speed and agility, injury prevention, preparation for the field, and mental toughness. The coaches showed how they controlled time, space, flow and efficiency in their coaching practices in an attempt to achieve their desired outcomes. A full map of the desired outcome discourses (i.e., strength/power, muscle size, speed/agility, injury prevention) and the specific coaching practices used to achieve them by controlling time, space, flow, and efficiency will be provided in the poster presentation. For example, the strength/power outcome discourse was associated with practices having athletes do squat, bench, and weightlifting movements by strictly dictated rest periods (i.e., controlling time), ensuring ideal and efficiently repetitive technique (i.e., controlling space), progressing athletes according to the plan of the periodization (i.e., controlling flow), and using commands to ensure significant effort performed (i.e., efficiency). Conclusion: This qualitative study extends the sociology of sport and psychosocial aspects of S&C by elucidating powerful YouTube videos. The sociological framework and conceptual tools showed what discourses and practices are dominant in the S&C field. However, the findings raise questions for how and why marginalized discourses and practices that too have been shown to enhance performance outcomes (i.e., pedagogy, motivation, well-being, alternative training methods) were not prevalent in the YouTube videos. Practical Applications: For coach educators, the NSCA, and sport science faculty, the findings help understand how S&C is conveyed on social media and therefore can generate hypotheses to be tested and educational programs that better prepare coaches towards critical understandings of social media discourses and practices. For S&C professionals, the findings show how power-knowledge flows in S&C, so that they can become more reflective problem solvers and creative in their practices.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

A Learning Community Approach Towards Developing Creative Strength and Conditioning Practices

B. Gearity1 and C. Kuklick2

1University of Denver; and 2Master of Arts in Sport Coaching/Graduate School of Professional Psychology/University of Denver

Sociologists of sport coaching have shown how sport coaches and strength and conditioning (S&C) coaches use physical science knowledge in an attempt to enhance athletic performance, however, these “disciplinary practices” result in unintended consequences that undermine athlete underperformance (i.e., athletes' apathy, injury, lack of decision making; Denison, 2007 Gearity & Mills, 2012). Drawing upon the work of eminent social theorist Michel Foucault, many social science studies repeatedly show that coaches are generally unaware of how power and knowledge operate through disciplinary practices (i.e., strict control of space, time, flow, efficiency), and thus coaches are unable to problem solve resulting concerns. To date, no research has attempted to educate S&C coaches to be aware of these disciplinary practices, and thus better understand how power and knowledge inform coaches' practices. Thus, it may be possible to enhance performance and reduce the unintended consequences of disciplinary practices. Purpose: The purpose of this exploratory qualitative case study was to deliver an educational intervention via a learning community (LC) to educate coaches on power, knowledge, and disciplinary practices. Methods: Three interscholastic S&C coaches and 2 researchers participated in 7 LC meetings. Data were collected from audio recordings of the LC meetings and the researchers' field notes. We conducted a rigorous qualitative analysis that grouped the data into themes to creatively problem solve disciplinary practices. Results: The LC resulted in new knowledge and practices contra disciplinary practices. Disrupting the control of time resulted in the theme spasmodic tempo training, defined aspractices that use time in various, discontinuous, and multifaceted ways; and atemporal training, which uses time as a sensation or un-quantifiable digit. Disrupting space resulted in variable geographic training, meaning practices that use space within the facility and in training programs in diverse, unconventional, and versatile ways; and variable intra-geographic training, which were practices that engaged athletes in exploring exercise through inter and intra-planer space. Disrupting flow resulted in a fluid and fragmented periodization, defined as constantly changing and flexible practices to plan athletes' performance. Disrupting efficiency resulted in explorative coaching that is practices for athletes' to self-regulate and explore their bodies; and strength coach as sage where coaches engage in a non-hierarchical and egalitarian philosophy of athlete-coach relations. Conclusion: From this sociological intervention, several new conceptual tools were developed to disrupt disciplinary practices and overcome their associated negative outcomes. Interestingly, some non-dominant exercise science, biomechanics, psychological, and motor learning research support many of the approaches, which offers grounds for future research and theorizing. Practical Applications: S&C coaches may benefit from using the findings as thinking tools to create ways of disrupting disciplinary practices that might otherwise go unrealized. Further interdisciplinary research is warranted that investigates empirical evidence on these S&C practices from bio-physiological, psychological, and sociological approaches.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Factors Influencing the University Choice of NCAA Division I and Division II Latino Student-Athletes

M. Silva and L. Diaz

University of Puerto Rico—Mayaguez

Participation of student athletes from Latino background in the National College Athletic Association (NCAA) Division (DI), Division (DII), and Division (DIII) have been documented for decades; however, research focusing on college choice factors of Latino student-athletes is still limited or even non-existent, even though the enrollment of Latinos in higher education continues to grow as well as their participation in college athletics. For Latino student athletes when it comes to choosing a particular institution and athletic division can be difficult because there are different reasons why student athletes decide to choose or not to choose a particular college or university. The purpose of this study was to determine if the factors that influenced the college choice of DI Latino-athletes were different than the factors that influenced the college choice of DII Latino student athletes. Methods: A total of 59 males and 92 females (ages ranged from 18 to 25 years) student athletes from the NCAA DI member institutions, and 74 males and 48 females (ages ranged from 18 to 25 years) student athletes from the NCAA DII member schools participated in this study. This investigation was descriptive and an electronic survey-based design and questions were presented for data collection. The choice factors for choosing a particular institution analyzed in this study were: a) the academic major, b) the athletic program, c) coaching staff, d) location, e) financial aid, and f) other. Results: Statistical analysis showed that 25.2% of Latinos student athletes of NCAA DI member institutions chose their current college or university because the athletic program, 20.5% because the academic major, 16.6% because the financial aid, 13.3% because other reasons, 12.6% because the location, and 11.9% because coaching staff. For Latino student athletes of NCAA DII institutions, results showed that 72.4% of the participants chose their current school because the academic major, 8.9% because the location, 8.1% because the athletic program, 4.1% because coaching staff, 4.1% because financial aid, and 2.4% because other reasons. Conclusion: The present study found that the highest percentage of DI student athletes chose their current institution because the athletic program. For DII participants the highest percentage showed that the academic major was the main reason for choosing their current school. Practical Applications: These finding are valuable information for the coaching and athletic department staff of DI and DII colleges and universities to the successful recruitment of student-athletes from Latino backgrounds.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Leader Priming Impacts Exercise Psychophysiological Responses to High Intensity Mixed Modal Exercises

D. Hollander, J. Dolese, A. Colton, B. Baiamonte, and R. Kraemer

Southeastern Louisiana University

Given that social priming, the suggestion of positive or negative experiences prior to an event, can impact behaviors and affect responses, it is reasonable to conclude that this may happen in an exercise setting. Anticipating exercise intensity can alter subjective experience by manipulating perception. Since leaders are uniquely positioned to gear participants toward expected intensities, participants are likely to base some of their experiences of exercise intensity from cues relayed by the coach prior to the session. This may be particularly true in group-exercise sessions. However, data are lacking related to the psychophysiological changes that can manifest from this potent social agent. Purpose: To compare positive and negative leader cues prior to a high intensity mixed modal exercise circuit on resultant responses to heart rate, RPE, pain, and affective reactions immediately after cessation of the exercise bout. Methods: Seventeen participants (32.07 ± 10.12 years, n = 9 men, n = 8 women) were recruited to participate in the study. All participants were given brief health history questionnaire, informed consent, a CR-10 pain scale, session RPE rating (6–20), and the subjective experiences of exercise scale (SEES) that measures psychological well-being, psychological distress, and fatigue. A brief warm-up was performed before participants did 3 rounds of squat thrusters and pull ups with repetitions of 21, 15, and 9, respectively. Minimal rest intervals were used. Results: Mean comparisons demonstrated a significant difference by group with the positive priming group having more women (n = 6) compared to the negative priming group (n = 1) more men in the negatively primed group (p < 0.01). Pearson Product Moment Correlations revealed a significant positive relationship between condition and HR (r = 0.44, p < 0.05) and fatigue (r = 0.50, p < 0.05). Other variables significantly related were pain and fatigue (r = 0.50, p < 0.05) and HR (r = 0.46, p < 0.05), RPE with fatigue (r = 0.45, p < 0.05) and HR (r = 0.47, p < 0.05), psychological distress with HR (r = 0.41, p < 0.05), psychological well being (r = −0.58, p < 0.01) and fatigue (R = 0.42, p < 0.005). These results indicate that negative priming was related to higher levels of psychophysiological response including negative affective reactions like distress and fatigue. Conclusion: The present study demonstrated that a leader who primed participants with positive cues and expectations had less negative psychological reactions after the session. Prospectively, these results indicate that leader cues, as a social primer, can influence psychophysiological response to a challenging exercise bout. Much more data is needed to confirm or refute this finding. Practical Applications: Strength coaches should consider leadership priming for intensity of exercise as a contributing factor to psychophysiological responses of their athletes and exercisers when beginning their routines.

F18
Figure 1.:
Correlations Between Variables and Priming Conditions. When priming comparisons were made, negative priming demonstrated positive significant relationships with fatigue and Heart Rate. *signifies p < 0.05, **signifies p < 0.01.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Perceptions of Body Image and the Drive for Muscularity in College-Aged Women

K. Skemp,1 S. Joecks,2 R. Elwood,3 and D. Baumann1

1University Wisconsin La Crosse; 2University of Wisconsin La Crosse; and 3Winona State University

Introduction: Body image distortion and dissatisfaction can play a role in unhealthy compensatory behaviors, such as disordered eating and compulsive exercise. Research supports that men usually desire to be more muscular, while women desire thinness. However, recent media coverage indicates that there may be a shift in women's desires from thinness to being more toned, fit, and muscular. Purpose: There is little research evidence to indicate that women are starting to behave more like men in regards to body image perceptions and therefore, body composition goals. This study sought to answer the question, “Is strong the new skinny” among college-aged women. Methods: A sample of 15 women (mean age = 20.73 ± 1.71 years, mean BMI = 25.7 ± 3.57) completed the study. Participants' perception of their current body composition (body fat and lean body mass) and their desired body composition was assessed using the somatomorphic matrix. The matrix is a bi-dimensional computerized body image test that assesses body image perceptions and satisfaction with respect to body fat and muscularity using contoured drawn silhouettes. Participants were asked to answer the following questions: (1) What do you think you look like? (2) Where would you ideally like to be? Two questionnaires, the Drive for Muscularity Scale (DMS) and the Muscle Dysmorphia Inventory (MDI) were also administered to further assess body image and muscle building behaviors. After completing the surveys, body fat and lean body mass were measured using air displacement plethysmography. Results: Mean measured body fat percentage (27 ± 6) was significantly higher than perceived body fat (23.2 ± 6.27) (p = 0.011). Furthermore, perceived body fat percentage (23.2 ± 6.27) was significantly higher than participants' desired goal body fat (16.27 ± 3.84) (p = 0.001). Mean perceived lean body mass (20 ± 2.64) was significantly lower than participants' desired goal lean body mass (23.10 ± 3.39) (p = 0.001). There were fair correlations between goal body fat and DMS questions, “I think my arms (0.59) and legs are not muscular enough.” (0.75) There were fair correlations between desired goal lean body mass and the MDI supplement (0.54) and the size/symmetry (0.63) subscales. Conclusion: This sample of women desired lower overall body fat as well as greater lean body mass or more muscle mass by selecting images representative of a leaner, more muscular physique on the matrix. Furthermore, they underestimated their actual body fat percentage by approximately 4%. Combined with their desire to lose approximately 6.9% body fat (perceived BF minus goal BF), these women desire approximately an 11% reduction in body fat (from their measured BF to their goal BF). Drive for muscularity behaviors (DMS) indicated participants responded “always” to “often” on questions desiring a more muscular physique and lifting weights to build muscle. Behaviors as measured by the MDI indicated that as participants' goal LBM increased, the use of supplements increased as did their concerns for building more muscle. However, overall scores did not indicate any pathological behaviors toward muscle dysmorphia among this sample of women. Practical Applications: It would appear that women desire a more toned, muscular physique, but at the same time, looking to lose body fat. Practitioners should be well versed in recognizing healthy and unhealthy body composition goals and behaviors among the women they serve.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

The Effects of Music Tempo on Perceived Exertion and Motivation to High-Intensity Functional Training

M. Zaghloul,1 J. Beamish,2 R. Pettitt, and J. Dexheimer

1Azusa Pacific University; and 2Point Loma Nazarene University

Introduction: High-Intensity Functional Training (HIFT) exercise programs are designed to target endurance and strength to improve physical health. However, these workouts are strenuous, which may make them less appealing to the general population. Though there is minimal evidence to suggest that music tempo plays a role in HIFT workout performance, music tempo has previously improved high intensity exercise performance, delayed fatigue, enhanced motivation, and increased enjoyment. Purpose: The purpose of this research study was to examine the effects of low (90–100 bpm), moderate (120–130 bpm), and high (150–160 bpm) music tempos on time to completion, rate of perceived exertion (RPE), and motivation during a HIFT workout. Methods: 7 functionally trained participants (Age 22.85 ± 26.17 years, Height 177.14 ± 12.41 cm, Weight 78.85 ± 7.58 kg) performed a HIFT workout completing a 1000 m Row, 50 thrusters, and 30 pull ups as fast as possible. The workout was completed under 4 randomized conditions in the following order: slow tempo, high tempo, no music, and moderate tempo. Upon completion of each session, workout time to completion was recorded (TM0, TM90, TM120, TM150), participants RPE was assessed using the Borg Scale (RPE0, RPE90, RPE120, RPE150), and motivation was surveyed using the Brunel Music Rating Inventory (BMRI-3) (BMRI90, BMRI120, BMRI150). A Friedman test was performed to measure the effect of music tempo on work-out time to completion, RPE, and motivation. A Wilcoxon signed-rank post hoc analysis was used to detect any significant differences between groups. A Bonferroni correction adjusted the alpha level (0.05/6) to 0.008 for work-out time and RPE and to (0.05/3) 0.017 for motivation. Results: Friedman tests revealed significant differences between music tempo for time to completion (p = 0.007; χ2(3) = 12.1), RPE (p = 0.005; χ2(3) = 12.8), and motivation (p = 0.034; χ2(2) = 6.7). Though, due to small sample size, low power, and an adjusted alpha level, the Wilcoxon signed-rank tests only revealed trends towards significance. Time to completion between different tempos displayed a trend towards significance between TM0 and TM120 (z = −2.366; p = 0.018; d = 0.34), TM90 and TM120 (z = −2.371; p = 0.018; d = 0.34), TM90 and TM150 (z = −2.028; p = 0.043; d = 0.29), and TM120 and TM150 (z = −1.859; p = 0.063; d = 0.27). RPE between different tempos also revealed a trend towards significance between RPE0 and RPE90 (z = −2.264; p = 0.024; d = 0.14), RPE0 and RPE120 (z = −2.041; p = 0.041; d = 0.29), RPE90 and RPE150 (z = −2.041; p = 0.041; d = 0.29), and RPE120 and RPE150 (z = −2.232; p = 0.026; d = 0.32). Lastly, motivation between different tempos demonstrated a trend towards significance between BMRI90 and BMRI150 (z = −1.782; p = 0.075; d = 0.25) and BMRI120 and BMRI150 (z = −2.371; p = 0.018; d = 0.34). Conclusion: In conclusion, results displayed that moderate tempo music may negatively influence HIFT time to completion. Although there was no significance shown for RPE and motivation trends indicate high tempo music may increase motivation and decrease RPE during a HIFT workout. Practical Applications: Knowing that HIFT is a vigorous activity, high tempo music may reduce perceived exertion and increase motivation which may increase levels of enjoyment and adherence to this type of exercise program. Further investigations should examine moderate tempo music with HIFT as it may negatively influence time to completion, perceived exertion, and motivation on a HIFT workout.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Assessing the Impact of Lab Technician vs. Subject Administrated Resistance on Wingate Performance

A. Bosak,1 M. Sokolowski,2 C. Carver,1 R. Sanders, J. Kelly,1 T. Bohon,1 H. Nelson,1 and J. Feister

1Liberty University; and 2Texas Women's University

The Wingate cycle ergometer test (WCET) is a widely utilized sports performance test which can yield peak power, mean power, and fatigue index values. Accurate assessment of these specific values are necessary in order for strength and conditioning professionals to use these values for the design of the most appropriate training programs for their athletes. Multiple studies have been conducted assessing the performance of various athletic and highly fit individuals on the WCET and the resistance that these individuals cycled against was applied by the lab technician. However, no prior study has evaluated the effects of lab technician administered resistance vs. subject administered resistance. Purpose: To evaluate the differences in peak power, mean power, and fatigue index using a Wingate cycle ergometer test where the resistance is administered by the subject and then another WCET where the resistance is administered by the lab technician. Methods: In a counterbalanced order, male (n = 39) subjects of no less than averagely fit status completed a WCET at maximum revolutions per minutes (rpms) at a resistance of 7.5 percent of the subject's bodyweight (in kg) for 30 seconds. During this test, either the lab technician (LTA) or subject (SA) administered the resistance that was cycled against. Seventy-two hours later, subjects completed another WCET using the alternative resistance administration technique that they did not use for the first WCET session. Peak power (in Watts), mean power (in Watts), and fatigue index (expressed as a percent) were compared using Paired-Samples t-Tests with significant differences occurring at p ≤ 0.05. Results: Although the results slightly favored SA, differences between peak power for SA (963.16 ± 195.56 W) vs. LTA (959.59 ± 193.02 W), for mean power for SA (683.69 ± 107.69 W) vs. LTA (682.83 ± 104.70 W), and fatigue index for SA (56.23 ± 7.96%) vs. LTA (56.28 ± 8.68%) were not significant. Conclusion: The results of the current study suggest that having resistance applied by a lab technician vs. the subject during a Wingate cycle ergometer test does not significantly effect peak power, mean power, or the fatigue index. Practical Applications: Although differences were not significant in this study, 59% of the subjects performed (i.e., generated higher peak and mean Watts) better during the WCET when they applied their own resistance. Thus, it is logical to assume that these individuals may be intrinsically motivated and therefore, it may be necessary to consider giving subjects a choice to apply their own resistance during a WCET if they appear to be intrinsically motivated. Likewise, if a subject is more extrinsically motivated, it may be wise to have the lab testing administrators/technicians apply the resistance during a WCET. Further research is needed to determine if changes in fitness level, cycling experience, motivation, age, or utilizing females may impact the administration of resistance and subsequent WCET performance.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Assessing the Relationship Between Enjoyment Level and Metabolic Responses During Skiing Ergometer Activity

H. Nelson, A. Bosak, M. Phillips, R. Lowell, B. Ziebell, M. De Moors, A. Blackley, A. Lau, A. Frech, and A. McCarty

Liberty University

Exercise adherence is largely determined by exercise enjoyment. Therefore, when introducing a new form of exercise training or testing, the level of enjoyment experienced by the exercising individual needs to be considered. A skiing ergometer (SE) is a form of aerobic and anaerobic exercise widely used for total body training. SE provides low impact exercise, lower cost equipment, and minimal required floor space. Additionally, use of the SE can be adapted for most individuals and the exercise technique can be learned rather easily. Because of the benefits, the SE may be a viable alternative max or peak graded exercise test (GXT) mode. However, whether the individuals enjoy the activity or not could potentially affect the elicited values of metabolic response, time to exhaustion, and heart rate. To the best of the researchers' knowledge, a correlation of enjoyment and metabolic responses on a skiing ergometer has not been assessed. Purpose: To examine the relationship between level of enjoyment and metabolic responses during a maximal aerobic capacity skiing ergometer GXT. Methods: Descriptive data (Ht., Wt., BF%, age) was measured for 22 averagely fit college-age males. Subjects completed a GXT to the point of volitional exhaustion on a skiing ergometer. The protocol began with a 2-minute warm up at a resistance of 30–40 Watts (W) and then increased by 20 W every minute until the subject reached volitional exhaustion. Within 10 minutes of completing the GXT, subjects were asked to complete a Physical Activity Enjoyment Scale (PACES). Peak or max Vo2, HR, and time to exhaustion (TTE) were recorded. Pearson Correlations were performed between Vo2, HR, TTE, and PACES score with significance at p ≤ 0.05. Results: There was no relationship between PACES and Vo2 (r = 0.134, p = 0.277), PACES and HR (r = 0.053, p = 0.407), and PACES and TTE (r = −0.015, p = 0.474). Conclusion: Enjoyment level appears to not have a relationship with metabolic responses during skiing ergometer GXT in no less than averagely fit males. Practical Applications: The results of the present study suggest that level of enjoyment may not be accurately used to predict metabolic responses during an assessment of maximal aerobic capacity on a skiing ergometer in no less than averagely fit males. Although statistically speaking, there was no relationship between enjoyment level and metabolic responses, high levels of enjoyment were reported by the subjects indicating that they found satisfaction in the SE exercise. Because enjoyment is vital to exercise adherence, the provided anecdotal evidence suggests that the skiing ergometer could be an adequate exercise mode for low impact cross-training or off-season training in athletes due to the high levels of enjoyment elicited. The PACES survey after skiing activity indicated an average score of 100.41 which is exceptional in terms of level of enjoyment for a mode of exercise. Future research should assess the relationship between enjoyment and metabolic responses in populations with higher levels of fitness, females, and protocol variations during skiing ergometer exercise.

Thursday, July 11, 2019, 12:00 pm–1:30 pm

Sex Related Differences in Percent of One-Repetition Maximum and Repetitions Completed at Critical Resistance

T. Dinyer,1 M. Byrd,1 A. Vesotsky,1 P. Succi,1 and H. Bergstrom2

1University of Kentucky; and 2university of Kentucky

Theoretically, critical resistance (CR) is the highest sustainable resistance that can be lifted for repetitions without fatigue. The CR reflects the asymptote of the resistance versus repetitions relationship and is estimated from the slope of the linear total work (resistance [kg] × repetitions) versus repetitions relationship during resistance exercise (RE) modalities (Figure 1). It has been suggested the CR may be related to the point of compromised blood flow and reflects differences in individual submaximal performance capabilities. Current evidence also indicates women tend to be more fatigue resistant than men, which has been attributed to variability in muscle properties (i.e., size or fiber type) and/or muscle metabolic system capacities. Purpose: To examine the differences in the percent of one-repetition maximum (1RM) corresponding to the CR (%1RMCR), as well as the number of repetitions completed to failure at CR between men and women. Methods: Ten men (Age: 24 ± 5 years; Height: 177.8 ± 7.6 cm; Weight: 87.1 ± 14.8 kg) and 10 women (Age: 31 ± 8; Height: 166.6 ± 6.5 cm; Weight: 66.2 ± 6.7 kg) completed 1RM testing for the deadlift (DL). On 4 separate days, repetitions to failure were completed at 50, 60, 70, and 80% 1RM, in a randomized order. Total work was plotted against repetitions completed at each resistance to derive the CR for each subject (Figure 1B). Repetitions to failure were then completed at the CR on a separate day. Mean differences for the 1RM (kg), CR (kg), %1RMCR, and repetitions completed at CR were examined with independent samples t-tests at an alpha of p ≤ 0.05. Results: The men had a higher 1RM DL (Men: 168 ± 27 kg; Women: 115 ± 11 kg; p < 0.001) and absolute CR (Men: 62 ± 14 kg; Women: 48 ± 6 kg; p = 0.011) than the women. The women, however, had a higher %1RMCR (Men: 37 ± 6%; Women: 41 ± 2%; p = 0.047) and completed more repetitions at the CR (Men: 45 ± 14; Women: 58 ± 12; p = 0.031), compared to the men. Conclusion: In the present study, although the men demonstrated greater absolute strength, the women performed more repetitions to failure at a greater relative CR (%1RMCR). This suggests sex differences in submaximal RE performance capabilities that may be related to the variability in muscle properties and/or muscle metabolic system capacities that dictate fatigability, such as muscle mass, blood flow, fiber-type composition, substrate utilization, and/or motor unit activation strategies. Practical Applications: The results of the present study indicated women were more resistant to fatigue than men during DL RE performed to failure. Some variability in individual submaximal performance capabilities may be accounted for by sex differences in fatigability. The CR may provide a useful model to examine submaximal performance capabilities to improve individualized resistance training prescription between men and women at low-loads.

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Figure 1.:
A) Theoretically, the critical resistance (CR) represents the highest sustainable resistance that can be lifted for repetitions without fatigue and may reflect the point of compromised blood flow and differences in individual submaximal performance capabilities. B) The relationship between total work and repetitions completed is described by the linear equation total work = a + b (repetitions), where a is the y-intercept and b is the CR.

Thursday, July 11, 2019, 1:00 pm–1:15 pm

Effects of Inter-Limb Asymmetries on Acceleration and Change of Direction Speed: A Between-Sport Comparison of Professional Soccer and Cricket Athletes

C. Bishop

Middlesex University

Purpose: Inter-limb asymmetries have been a popular line of investigation in recent years; however, there is a paucity of data examining the association with measures of physical performance and in professional athlete populations. The purpose of the present study was twofold: 1) determine the relationship between inter-limb asymmetries and speed and change of direction speed performance and, 2) compare these findings across professional soccer and cricket athletes. Methods: Professional soccer (n = 18) and cricket (n = 23) athletes performed single leg countermovement jumps (SLCMJ) on a force plate operating at 1,000 Hz, single leg drop jumps (SLDJ) using an optical measurement system, a 10 m sprint and 505 change of direction speed (CODS) tests. Inter-limb asymmetries were calculated as a standard percentage difference, independent samples t-tests conducted to establish systematic bias between groups, and Spearman's r correlations performed to establish the relationship between asymmetry and speed and CODS performance, with statistical significance set at p < 0.05. Results: The findings showed that professional soccer athletes sprinted faster, jumped higher and had a greater reactive strength index score during the SLDJ than cricket athletes (p < 0.05). In contrast, cricket athletes showed significantly faster ground contact times (p < 0.05) compared to soccer players. When calculating asymmetry, no significant differences were noted between groups during the SLCMJ; however, cricket athletes were significantly more asymmetrical than soccer athletes for jump height (p = 0.015; asymmetry = 11.5% for cricket and 6.5% for soccer) and reactive strength index (p = 0.014; asymmetry = 10.4% for cricket and 6.0% for soccer). In addition, these same metrics were significantly correlated with slower 505 times in the cricket group only (r = 0.56 to 0.74; p < 0.01). Conclusion: In summary, inter-limb asymmetries calculated from the SLDJ test were able to differentiate between professional soccer and cricket athletes, with those inter-limb differences also associated with slower CODS performance in cricketers. These findings highlight that the magnitude of asymmetry may in part play a role in slower CODS performance. Practical Applications: Given these findings, it seems prudent to suggest that the reduction of inter-limb asymmetries may be warranted for this professional cricket population. Previous literature has highlighted that both bilateral and unilateral training interventions may be used for the reduction of asymmetries; however, the research on such training interventions is limited. Given that asymmetries were shown during a unilateral task, it seems prudent to suggest that this cricket population should focus on a combination of unilateral strength and jumping-based exercises to reduce existing side-to-side differences over time.

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Thursday, July 11, 2019, 1:15 pm–1:30 pm

The Potentiation Effects of a Sled-Towing Load Corresponding to a 50% Velocity Decrement on Subsequent Sprint Time in High-School Soccer AThletes

J. Williams, R. Herron, L. Cosio-Lima, B. Spradley, and J. Wallace

United States Sports Academy

Heavy-sled towing is often used as a training- or post-activation-potentiation (PAP) stimulus to improve sprint performance. Generally, sled-loads are often prescribed as a function of an athlete's body weight (i.e., 50% body weight loaded on sled). However, due to friction-related variables, the actual resistance imposed on the athlete can be influenced by sled design and running surface. Therefore, the utility of a standard, percent-body-weight load is limited. Sled-loads, based on velocity decrement, may provide more uniformity in strength and conditioning program design and related outcomes. Purpose: The purpose of this study was to determine if a PAP protocol aimed at » 50% velocity decrement (V−50%) would improve subsequent, 15-m sprint time in high-school soccer athletes. Methods: Fifteen high-school soccer athletes [n = 15 (female; n = 9) age range; 15–19 years] participated in this study. During visit one, weight (males = 71 ± 12 kg; females = 56 ± 6 kg) and baseline 15-m sprint times were assessed. Following a standardized, dynamic warm-up, an electronic-timing system recorded three 15-m sprint times for each participant. The best time of 3 attempts was recorded and used for analysis (S1). On visit 2, participants completed the standardized warm-up and were outfitted with a waist-harness for V-50% sled towing loads. Researchers were able to load the sled with an appropriate weight to elicit » V-50% (i.e., a time that was twice a long) within 3, 15-m sprint attempts. A slight range of velocity decrement was permissible (40–50%) due to limitations from rounding of times and the interval nature of the weighted-plates used to load the sled. The target sled weight was recorded and used during the third visit, as part of the PAP protocol. During visit 3, participants repeated the standardized warm-up and then completed 3 repetitions of 15-m sprinting pulling the » V−50% sled-load. Each repetition was separated by 2-min of recovery. After completing all 3 PAP reps, the participants then completed 3 additional 15-m, unloaded sprints of which the best time was used for post-intervention analysis (S2). Results: A one-tailed, paired-samples t-test revealed significant improvements in sprint time following the sled-towing PAP protocol (S1 = 2.70 ± 0.09 seconds vs. S2 = 2.60 ± 0.10 seconds; p < 0.0001; Cohen's d = 0.92). Conclusion: Sprint performance significantly improved following the PAP intervention of 3 repetitions with a load corresponding to » V−50%. Additionally, 13/15 participants showed improvement. Practical Applications: These findings support the use of prescribing PAP sled-towing protocols relative to a change in velocity in order to improve reliability and best practices. This standardization can better serve coaches, due to the variability in sled equipment used and running surfaces. Strength and conditioning coaches and researchers should use velocity decrement as the variable of interest when utilizing and investigating sled-towing interventions.

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Thursday, July 11, 2019, 1:30 pm–1:45 pm

A 10-Month High-Intensity Interval Neuromuscular Training Program Improves Fundamental Movement Patterns in Previously Inactive Obese Women

A. Batrakoulis,1 D. Draganidis,1 K. Papanikolaou,1 C. Deli,1 P. Tsimeas,1 A. Chatzinikolaou,2 V. Laschou,1 K. Georgakouli,1 A. Jamurtas,1 and I. Fatouros1

1University of Thessaly; 2Democritus University of Thrace

Introduction: Sedentary obese adults demonstrate impaired functional capacity while the obesity epidemic is expanding at an alarming rate worldwide. On the other hand, high-intensity interval training (HIIT), small group training, and functional fitness are currently the most prevalent trends in the global fitness industry. Purpose: This randomized controlled trial investigated the effects of a high-intensity interval neuromuscular training program on fundamental movement patterns in previously inactive obese women. Methods: Forty-nine premenopausal obese female volunteers (n = 49; age: 36.4 ± 4.4 years; body mass index: 29.1 ± 2.9 kg/m2; body fat: 46.8 ± 5.0%) were randomly assigned to either (i) a control group (C, n = 21; participated only in measurements), (ii) a training group (TR, n = 14), or (iii) a training-detraining group (TRD, n = 14). The exercise protocol was a supervised, low-volume, progressive, and time-efficient (<30 minutes) training program that included 10–12 neuromotor exercises with adjunct modalities at prescribed work-to-rest intervals (20–40 seconds) in a circuit fashion (1–3 rounds) on nonconsecutive days for 10 months. The Functional Movement Screen testing battery (FMS) was used to assess the 7 fundamental movement patterns that each was scored from 0 to 3 points, with the sum creating a total score ranging from 0 to 21 points. The Wilcoxon signed-rank test was used to determine the time-effect and perform pairwise comparisons. Differences for all dependent variables among groups were examined using the Mann-Whitney U test. Results: In TR, FMS total score increased from baseline to mid- (+45%, z = 3.314, p = 0.001) and post-training (+53%, z = 3.317, p = 0.001). In TRD, FMS total score increased from baseline to mid-training (+38%, z = 3.320, p = 0.001) and remained above pre-training levels following detraining (+30%, z = 3.086, p = 0.002). At mid-training, FMS total score demonstrated similar values in TR and TRD and they were both higher than C (TR vs. C: +50%, U = 0.000, p = 0.000; TRD vs. C: +46%, U = 0.000, p = 0.000). At post-training, TR demonstrated higher FMS total score than C and TRD (TR vs. C: +57%, U = 0.000, p = 0.000; TR vs. TRD: +15%, U = 37.000, p = 0.004) while TRD showed higher FMS total score than C (+36%, U = 7.000, p = 0.000). Conclusion: There is a limited amount of data examining this kind of functional assessments in sedentary obese adults following a long-term exercise intervention. This study suggests that a nontraditional, time-efficient and injury-free training program that integrates HIIT and movement-based resistance training with alternative modalities improves fundamental movement patterns in previously inactive obese women. Practical Applications: This novel and time-efficient exercise mode highlights the importance of using a supervised HIIT-type group program adapted to physiological needs of this cohort in the real-world gym setting.

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Figure 1.:
FMS Total Score. FMS total score changes during the 10-month experimental period.

Thursday, July 11, 2019, 1:45 pm–2:00 pm

The Effect of Acute Chronic Training Load Ratio on Daily Sleep Duration and Quality in a NCAA Division 1 Soccer Player

Y. Sekiguchi,1 R. Curtis, R. Huggins,2 C. Benjamin,2 W. Adams,3 S. Arent, R. Jain,4 S. Miller,5 and D. Casa2

1Korey Stringer Institute, Department of Kinesiology, University of Connecticut; 2Korey Stringer Institute, University of Connecticut; 3University of North Carolina, Greensboro, 4Northwestern University; and 5Penn State University

It is well-established that acute training load impacts sleep in an athletic population. However, no study to date has examined the impact of the acute:chronic work load ratio (ACWL) on sleep. Purpose: The purpose of this study was to investigate the effect of ACWL on daily sleep duration and sleep quality throughout a collegiate men's soccer season. Methods: Sixty-four male collegiate soccer players (mean ± SD; age, 20 ± 2 y; body mass, 77.3 ± 6.7 kg; height, 179.9 ± 6.4 cm; Vo2max, 53.0 ± 5.0 ml·kg−1·min−1) participated in this study, which took place during the 2016 and 2017 National Collegiate Athletic Association soccer seasons. For each training session and match, players donned a heart rate and GPS enabled chest strap to measure total distance covered (TD). Daily sleep duration and sleep quality were collected using the Karolinska Sleep Diary. Sleep duration was determined using self-reported bed-time and wake-time. Sleep quality was determined by asking participants to answer “How well did you sleep?” on a 1–5 Likert scale. Sleep duration and sleep quality were transformed to corresponding z-scores to account for individual differences. ACWL was calculated for TD using the ratio of the previous 7-day average to the previous 28-day average. The seven-day average was included in the 28-day average. ACWL values were categorized as low (ACWL < 0.85), medium (0.85 ≦ ACWL < 1.1) and high (ACWL ≧ 1.1). The number of observations between each category of ACWL was equal. One-way ANOVA with LSD pairwise comparison was used to assess sleep duration and sleep quality in different ACWL groups. Results: Sleep duration was significantly lower when ACWL was high compared to low (MD [95% CI], = −0.12 minutes [−0.25 to −0.001], p = 0.49) and medium (−0.14 [−0.26 to −0.012], p = 0.025) (Figure). There were no significant differences between groups in sleep quality. Conclusion: ACWL could impact daily sleep duration. A high ACWL was associated with shorter sleep duration compared to low ACWL and medium ACWL. Practical Applications: ACWL may be used to manage athlete's sleep duration to achieve better recovery. Strength and conditioning coaches and sport scientists should educate athletes to increase sleep duration when training load is high to achieve better recovery.

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Thursday, July 11, 2019, 2:00 pm–3:30 pm

Correlation of the Isometric Mid-Thigh Pull and the Isometric Squat Following High Volume Resistance Exercise

B. Gibson,1 J. Laudato,1 C. Dulaney, C. Trionfante,2 E. Tagesen,1 and A. Jajtner

1Kent State University; and 2Miami University

The isometric mid-thigh pull (IMTP) and isometric squat (ISQT) are assessments that can be used to monitor muscular performance. Their use, however, can be time consuming, and when used together may be redundant. Purpose: Therefore, in an attempt to eliminate the use of multiple tests to assess performance, the relationship between the IMTP and ISQT prior to, and following, resistance exercise designed to induce muscle damage was examined. Methods: Resistance trained men (n = 9; 22.67 ± 3.8 years; 175.19 ± 2.54 cm; 78.0 ± 7.0kgs) volunteered to complete 4 experimental visits. Participants were required to attain a 1- repetition maximum (1-RM) of 1.5x – 3x their respective body weight to qualify for the study. During visit 1, participants were asked to complete a 1-RM of the back squat, and complete a familiarization trial on the IMTP and ISQT. At least 72 hours later, participants returned to the lab for visit 2, and were asked to complete 8 sets of 10 repetitions of the back squat at 70% of their predetermined 1-RM with 2 minutes of rest between each set. Participants were asked to complete both performance measures (IMTP and ISQT) prior to exercise (PRE), as well as immediately (IP), 1-hour (1H), 24-hours (24H) and 48-hours (48H) after the exercise protocol. For both IMTP and ISQT, data were collected on bilateral force plates sampling at 1000 Hz. Both IMTP and ISQT were analyzed for the rate of force development (RFD) over the first 100ms and peak force (PF) averaged over 100ms. An average of 3 maximal attempts were taken at each time point. To ensure changes in performance occurred following resistance exercise, a one-way repeated measures ANOVA was employed to analyze differences between time points. Furthermore, IMTP and ISQT were correlated at each time point via Pearson Product Correlations. Results: Significant changes in PF for both IMTP (F = 19.248, p < 0.001, = 0.706) and ISQT (F = 10.041, p < 0.001, = 0.557) were observed from PRE across time. Briefly, significant decrements were observed from PRE at all time points for both IMTP and ISQT (p < 0.05). A significant main effect of time (F = 10.793, p < 0.001, = 0.574) was also observed for ISQT RFD, with significant decrements from PRE at all time points. A significant main effect of time (F = 3.134, p = 0.028, = 0.281) was also observed for IMTP RFD, with significant decrements from PRE to IP (p = 0.019) and PRE to 1HR (p = 0.003). Additionally, IMTP and ISQT PF were significantly correlated at all time points (r ≥ 0.828, p ≤ 0.01). IMTP and ISQT RFD, however, were only significantly correlated at 48H (r = 0.672, p = 0.047). Conclusion: Therefore, as a baseline measurement, as well as in the presence of exercise induced muscle fatigue and possibly damage, the IMTP and ISQT are similar measures in the assessment of peak force. When assessing the RFD, however, the IMTP and ISQT do not change in a similar fashion. Practical Applications: As a result, both the IMTP and ISQT are required to adequately assess performance, suggesting that the removal of one may be detrimental to the efficacy of future study results.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

The Effect of Scapular Taping on Shoulder Pain and Impairments Amongst Individuals With Subacromial Impingement Syndrome

R. Latimer,1 M. Kolber,2 S. Cheng,2 S. Wilson,2 T. Toole,3 E. Hutcherson,3 and W. Hanney

1Florida State University; 2Nova Southeastern University; and 3Florida State university

Introduction: Up to 67% of the population will experience shoulder pain in their lifetime, with evidence suggesting an increased incidence amongst overhead athletes and weight-training participants. Although the etiology of shoulder pain is multifactorial, subacromial impingement syndrome (SIS) is one of the more common diagnoses. Individuals with SIS may present with numerous impairments including but not limited to scapular dyskinesia and pain reaching overhead. Scapular dyskinesia has been associated with limited overhead range of motion (ROM) and altered muscle characteristics, thus interventions for individuals with SIS often seek to improve pain-free ROM and scapular muscle performance. Although various forms of taping are used by sports medicine professionals for musculoskeletal disorders, a paucity of evidence exists to support the use of taping for individuals with SIS. Purpose: Investigate the effect of elastic scapular taping on shoulder ROM, pain, and scapular muscle characteristics amongst recreationally active adults diagnosed with SIS (based on a valid clinical testing cluster). Methods: Thirty recreationally active adults (16 females, mean age 28.9) with SIS consented and completed testing with and without tape. Of the 30 participants, 24 participated in weight-training an average of 3 times per week and 11 participated in overhead athletic activities. The taping application consisted of one 25-cm. strip of elastic tape applied from the root of the scapular spine to the distal attachment of the lower trapezius. Given the consistent length of the tape, efforts were not made to standardize the degree of stretch during application. Dependent variables included electromyography (EMG) amplitude measurements (upper trapezius (UT), lower trapezius (LT), serratus anterior (SA)) during active humeral elevation in the scapular plane, hereafter referred to as scapular plane elevation. Additionally, pain and ROM quantity were assessed under both conditions during scapular plane elevation. Results: A significant increase in scapular plane elevation ROM (F(1, 29) = 4.872, p = 0.035) was present when comparing the taped versus un-taped condition. Additionally, taping produced a significant reduction in UT EMG peak amplitude when compared to the un-taped condition (F(1, 29) = 4.538, p = 0.042), however, significant differences were not present for the LT and SA (p ≥0.11). A Wilcoxon Signed Ranks test identified a significant reduction in pain (p = 0.03) during scapular plane shoulder elevation when taped as compared to the un-taped condition. Conclusion: The elastic taping application used in this investigation may improve pain free active ROM and favorably alter EMG amplitude ratios (UT to LT and UT to SA) amongst people with SIS. Limitations of the results reside in the small sample size and use of a design that lacks a true placebo. Practical Applications: Scapular muscle performance imbalances that favor elevated UT activity when compared to the LT or SA have been associated with scapular dyskinesia and shoulder pain. Thus, efforts to identify interventions, which may decrease UT amplitude without altering or by increasing LT or SA amplitude, may be beneficial for patients or clients with SIS. The elastic taping application used in this study may improve pain-free overhead ROM and muscle characteristics amongst recreationally active individuals with SIS.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Effect of Initial Supramaximal Accentuated Eccentric Loading on Subsequent Back Squat Velocity

M. Falzone,1 J. Merrigan,1 L. Biscardi,1 J. White,1 J. Oliver,2 and M. Jones1

1George Mason University; and 2Texas Christian University

Accentuated eccentric loading (AEL) may potentiate muscle activity and lead to enhanced concentric velocity, but results vary with lifting tempo and eccentric load. Weight releasers can be used to implement AEL, but due to their nature of use, evaluation of velocity generally is limited to one repetition (rep). However, the velocity of non-AEL reps following the initial AEL rep may be affected and has yet to be addressed. Purpose: To evaluate the effect of supramaximal AEL exercise with weight releasers on the velocity of subsequent non-AEL reps. Methods: Nineteen resistance-trained men (mean ± SD; training age, 6.3 ± 2.6 years; one repetition maximum (1-RM) back squat: body weight, 2.0 ± 0.3) completed 1-RM back squat testing and were familiarized with weight releasers (loaded to 55% 1-RM) in session 1. Session 2 took place 72 hours later and subjects were randomly assigned to AEL or traditional loading (TRA) and performed 3 sets of 5 reps at 65% 1-RM. Session 3 (AEL or TRA) occurred 48 hours after Session 2. Following the eccentric movement of rep 1 during AEL (120% 1-RM), the weight releasers disengaged; therefore, the concentric portion of the rep 1 and subsequent reps was 65% 1-RM. Testing was conducted with 4 linear position transducers attached to the barbell forming one triangle on each side. A software system was used to collect and analyze velocity data. Repeated measures analysis of variance (condition × sets × reps) was used to assess statistical significance (p < 0.05). Results: Condition × set interactions existed for mean (F(2,36) = 5.763, p = 0.007) and peak eccentric velocity (F(2,36) = 3.340, p = 0.047). During AEL, mean eccentric velocity in set 2 was −0.044 m·s−1 (CI 95%; −0.086, −0.001) faster than TRA. Peak eccentric velocity in set 2 and set 3 was −0.109 m·s−1 (CI 95%; −0.184, −0.034) and −0.090 m.s-1 (CI 95%; −0.149, −0.032) faster in AEL, respectively. Condition*rep interactions existed for mean concentric (p < 0.001), eccentric (p < 0.001), and peak eccentric velocity (p < 0.001). During rep 1, mean eccentric velocity was 0.094 m·s−1 (CI 95%; 0.046, 0.142; d = 0.88) greater in AEL. Contrary to AEL effects on rep 1, AEL produced faster eccentric mean velocity in rep 2 (p = 0.029; d = −0.54), rep 3 (p = 0.003; d = −0.69), rep 4 (p = 0.002; d = −0.78), and rep 5 (p = 0.043; d = −0.44). Likewise, eccentric peak velocity was faster in AEL for rep 2 (p = 0.007; d = −0.55), rep 3 (p = 0.001; d = −0.62), rep 4 (p = 0.002; d = −0.65), and rep 5 (p = 0.002; d = −0.58). Concentric mean velocity was faster in AEL for rep 3 (CI 95%; 0.004, 0.064 m·s−1) and rep 4 (CI 95%; 0.005, 0.065 m·s−1). Conclusion: During the initial rep, both eccentric and concentric velocity were impeded as a result of AEL. However, in later reps where the eccentric velocity was enhanced due to AEL, concentric velocity was also enhanced. This may suggest that the potentiating effect of AEL may not occur until later reps within a set. Practical Applications: To remain in control during supramaximal AEL, eccentric velocity may be reduced; however, eccentric actions of latter non-AEL reps within the same set may be enhanced. Thus, in order to achieve greater concentric velocity, it is recommended to include multiple reps when training with weight releasers in a supramaximal AEL protocol.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Effect of a Neoprene Knee Sleeve on Performance and Muscle Activation During a Leg Press Exercise

A. Stranieri, M. Bove, L. Vincent, J. Earp, and D. Hatfield

University of Rhode Island

Compressive neoprene knee sleeves are marketed to improve performance during resistance training exercise. They have been approved for competition by several different strength sport organizations, including the International Powerlifting Federation. However, there is currently minimal research examining whether wearing commercially available neoprene knee sleeves have a positive effect on resistance training performance. Purpose: The purpose of this study was to determine whether wearing a commercially available neoprene knee sleeve affects number of repetitions performed, blood lactate (BL), heart rate (HR), ratings of perceived exertion (RPE), or muscle activity during a leg press exercise. Methods: Seventeen resistance-trained individuals (11 men and 6 women; age: 21.7 ± 2.9 years; mass: 74.9 ± 9.2 kg; height: 1.7 ± 0.1 m) participated in 3 testing sessions, with each session being separated by one week. In the first session, participants performed one repetition maximum (1RM) testing on a plate-loaded leg press machine. In sessions 2 and 3, participants performed 6 sets at 80% 1RM until failure with 3 minutes rest between sets, either with knee sleeves (KS) or without (NS). The order of the KS and NS conditions were randomly determined for each subject. BL, RPE, and HR were collected after each set. Surface electromyography (EMG) of the vastus lateralis muscle was recorded to compare muscle activity during KS and NS conditions. The mean, max and integrated EMG (iEMG) of the middle 3 repetitions of every set were used for analysis. A one-way repeated measures ANOVA with Bonferroni post-hoc corrections were performed to assess the effect of knee sleeves on BL, RPE, HR, repetitions performed, and muscle activity. Significance was set at p ≤ 0.05 and values are presented as mean ± SD. Results: No significant differences were seen in total number of repetitions for all sets (p = 0.3; KS 77.8 ± 35.2, NS 83.3 ± 36.1) or number of repetitions per individual set between KS and NS conditions, within participants (Set 1 = KS 19.8 ± 8.8, NS 20.6 ± 10.3; Set 2 = KS 15.2 ± 6.7, NS 14.4 ± 5.2; Set 3 = KS 12.9 ± 5.5, NS 13.7 ± 5.6; Set 4 = KS 10.9 ± 5.8, NS 12.2 ± 6.2; Set 5 = KS 9.8 ± 4.9, NS 11 ± 6.3; Set 6 = KS 9.6 ± 6.5, NS 11.3 ± 6.3). No significance differences were seen for BL, HR, and RPE (p ≥ 0.05). For muscle activity, no significant differences were seen within participants (p ≥ 0.05) for mean, max, and iEMG between KS and NS conditions. Conclusion: These results suggest wearing compressive neoprene knee sleeves has no effect on improving performance and associated variables during lower body resistance training. Practical Applications: Despite their popularity, based on the results of the present study, wearing neoprene knee sleeves during high load, high volume lower body resistance training with the goal of improving performance is not supported.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Effects of Including Isometric Squat Training on 3RM Squat Performance in Powerlifters: A Pilot Study

D. Lum, J. Goh, and S. Soh

Singapore Sport Institute

Isometric strength training (IST) has been shown to improve maximum isometric and dynamic strength. It has been shown that when performed explosively, IST resulted in improved jump performance. However, no study has investigated the effects of replacing part of powerlifters' squat training with IST on squat performance. Purpose: The aim of this study was to investigate the effects of replacing 2 sets of heavy weight squat training with isometric squat on 3 repetitions maximum (RM) performance. Methods: Ten powerlifters (mean ± SD age; 29.5 ± 10.1) were recruited and were matched for strength level before randomly assigned to either control (Con) (n = 5) or isometric training (Iso) (n = 5) groups. Participants completed 1 familiarisation, 1 pre- and 1 post-tests sessions which included isometric mid-thigh pull (IMTP) and 3RM squat tests, and 24 training sessions over 6 weeks. Both groups performed similar training program which included the 3 main lifts, squat, deadlift and bench press, and other accessory exercises. All the main lifts were performed at between 65 and 85% of 1RM for 2–5 sets and 3–6 repetitions. Only squat was performed twice a week while deadlift and bench press were performed once a week. All accessory exercises were performed at RPE rating of between 7 and 8 for 3–4 sets and 8–16 repetitions. For Iso group, 2 sets of squats during each session were replaced with 2 sets of 5 repetitions of maximal isometric squats executed explosively and sustained for 3 seconds. One set was performed at bottom range of the squat and the other at 90° knee angle. Results: Post-test 3RM squat increased by 10.4 ± 5.7% (ES = 0.31) in Iso and 3.7 ± 3.5% (ES = 0.12) in Con, while IMTP peak force increased by 13.6 ± 6.0% (ES = 0.83) in Iso but decreased by 3.5 ± 12.1% (ES = 0.17) in Con. Large effect sizes were observed for the differences in percentage change between groups for 3RM squat (ES = 1.4) and IMTP (ES = 1.8). Conclusion: The current pilot study showed that replacing part of heavy weight squat training with maximal isometric squats resulted in higher increment in 3RM squat and IMTP peak force than a traditional powerlifting trainng program. Practical Applications: The results suggest that the addition of IST to a traditional powerlifting training program was effective in increasing maximal strength. We suggest that powerlifters can include IST as part of their training program. In addition, IST should be performed at the bottom range where concentric phase is initiated, and also at the biomechanically most disadvantage joint position of the specific exercise.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Impact of Spotter Sex on One-Repetition Maximum Bench Press Performance

B. Nickerson,1 G. Salinas,1 J. Garza,1 S. Cho,1 K. Park,1 and R. Snarr2

1Texas A&M International University; and 2Georgia Southern University

Resistance training exercises are popular due to their favorable health outcomes, particularly those associated with increased muscular fitness. For each exercise, proper load prescription may vary based upon the specific goals of the athlete using various metrics (i.e., percentage of one-repetition maximum (%1RM), mean velocity (MV), and peak power (PP). However, external variables (i.e., observers, motivation, etc.) are often neglected or unaccounted for during performance training and testing which may impact the participant. Limited research exists on the effect of spotter sex on resistance training, particularly during bench press performance. Purpose: The purpose of this study was to determine the impact of spotter sex on bench press performance during a 1RM testing protocol. Methods: Twenty resistance-trained individuals (10 males and 10 females) visited the lab on 2 separate occasions. During both visits, subjects had their 1RM (kg), MV (m/s), and PP (W) determined on a bench press 1RM protocol while using either a male or female spotter (i.e., counterbalanced design). Deception was utilized by telling subjects the intent of the study was to determine the reliability of a linear position transducer for measuring MV and PP during the 1RM trials. Wilcoxon signed rank tests were used for all comparisons between the male and female spotter trials with an a priori alpha level of 0.05. Results: The main findings revealed that measured 1RM values for male subjects were significantly higher than estimated 1RM values when utilizing both a male (p = 0.01; Cohen's d = 0.24) and female spotter (p < 0.01; Cohen's d = 0.25). Additionally, results revealed MV and PP were significantly higher for the 1RM trials when male subjects had a male spotter (both p < 0.01; Cohen's d = 0.67 and 0.25, respectively). Alternatively, there were no significant differences in estimated versus measured 1RM values for females as well as no effect of spotter sex on bench press strength (all p > 0.05). Conclusion: The current study indicates that measured 1RM scores appear to be similar for males and females regardless of spotter sex. In contrast, male subjects produced significantly greater MV and PP values in the presence of a male spotter whereas no differences occurred between spotters (i.e., male or female) within female subjects. It is possible that male subjects were more competitive with male spotters, which subsequently led to higher MV and PP values during the 1RM trials. Practical Applications: Prior to the current study, it was unknown how male and female spotters impacted bench press performance of resistance-trained individuals of the same or opposite sex. Strength and conditioning specialists and other health fitness professionals should note that sex of a spotter does not appear to impact measured 1RM, but may influence MV and PP.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Effect of Strength and Plyometric Training on Running Performance in High School Aged Long-Distance Runners

K. Asano, Y. Goto, C. Fan, J. Liu, and J. Uchimaru

Sendai University

Introduction: It is well known that strength and/or plyometric training would improve running performance. Furthermore, to date, there are few studies that focus on high school aged runners, but it is unclear that whether or not strength and plyometric training effect on running performance in high school runners. Purpose: We examine the effect of strength training including plyometric training on running performance in high school aged runners. Methods: Fourteen high school aged long-distance runners (Age: 16.1 ± 9.7 years; Body Mass: 54.1 ± 4.1 kg; Vo2max: 65.4 ± 3.0 ml/kg/min) participated in this study. Subjects separated into strength training intervention group (S, n = 7) and control group (C, n = 7). This study was approved by Sendai University IRB. Prior to the experiment, since subjects were minors, written consent was obtained from each subject's guardian. Intervention of strength training period was 20 weeks. S group completed 1-day heavy strength training (mainly used back squat; 65–90% 1RM) and 1-day plyometric drills in each week addition to running practice, while C group carried out only running practice. Before and after the experimental period, all subjects were completed a submaximal and maximal incremental treadmill test for measurements of running economy, HR and blood lactate concentration at submaximal exercise, Vo2max, and run time as running performance. Treadmill test were the 3 stages (velocity of 5.5, 4.5, and 3.5 min/km) for 3 minutes at 1% degree, then fourth stage started from the same velocity and grade as the third stage, and gradually increased by 1% grade every minute until exhaustion. There was a one minute rest between each set. %Vo2max at submaximal stages was determined by Vo2 at 3 different stages divided by Vo2max. Blood lactate was determined from arterialized capillary blood at the end of the each stages exercise. We also measured reactive strength index (RSI) that was assessed by 4 jumps and drop jump, countermovement jump (CMJ), knee extension/flexion isometric strength as relate to strength training. A paired T-test (2 sided) were performed across intervention (pre vs. post). Results: Vo2max significantly improved (p < 0.05) in E (from 65.9 ± 2.70 to 67.3 ± 2.98) compared to C (from 64.9 ± 3.09 to 68.7 ± 3.71). %Vo2max at first and third stage were significantly improved (p < 0.05) in E (from 61.5 ± 4.8% to 60.0 ± 4.8% and from 89.5 ± 3.8% to 86.5 ± 4.7%, respectively) compared with C (from 61.8 ± 4.8% to 59.2 ± 2.8% and from 92.3 ± 3.2% to 89.0 ± 2.9%, respectively). Both groups increment run time at fourth (from 5:47 ± 0:51 to 7:05 ± 0:50 in E, p < 0.001 and from 5:42 ± 0:39 to 6:47 ± 0:41 in C, p < 0.05) compared with the respective pre-test baseline. Drop Jump's RSI (m/ms) improved significantly (p < 0.05) in E (from 1.368 ± 0.49 to 1.692 ± 0.42) but not in C (from 1.197 ± 0.38 to 1.315 ± 0.29). Conclusion: From these results, intervention of strength training appears to improve Vo2max, running efficiency and run time as running performance and RSI in high school aged long-distance runners. Improved RSI may contribute to improve %Vo2max and increment run time. Practical Applications: The result of this investigation suggest that heavy strength and plyometric training have positive effect on RSI and may enhance running performance in high school aged runners.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Changes in Early and Maximal Isometric Force Production in Response to Moderate and High Intensity Strength and Power Training

P. Comfort,1 J. McMahon, T. Dos'Santos,1 P. Jones,1 C. Thomas,2 and T. Suchomel3

1University of Salford; 2Aspire; and 3Carroll University

Purpose: To determine the changes in early (50-, 150- and 250 ms) and maximal isometric force production, in response to a four-week period of moderate intensity training, followed by a 4-week period of high intensity resistance training. Methods: 34 subjects (age 19.5 ± 2.8 years; height 1.72 ± 0.08 m; body mass 69.9 ± 11.4 kg; relative one repetition maximum [1RM] power clean 0.92 ± 0.03 kg·kg−1) volunteered to participate in this study. Subjects performed the isometric mid-thigh pull (IMTP), on 2 occasions, 72 hours apart, at baseline, to determine reliability of the dependent variables. Testing was repeated after each phase of training. The IMTP was performed following a standardized protocol, with the participants standing on a force platform and adopting a posture which replicated the second pull position of the clean, (i.e., knee and hip angles of 144.3 ± 4.3° and 145.6 ± 4.4°, respectively). The moderate intensity training phase consisted of 3 sets of 5 repetitions at 60–82.5% 1RM, while the high intensity training phase consisted of 3 sets of 3 repetitions, at 80–90% 1RM, both performed twice per week, with 48–72 hours between sessions. Exercises included back squats, power clean derivatives, push press and Romanian deadlifts, with the sequence varying between phases. Repeated measures ANOVA with Bonferroni post-hoc analysis and Cohen's d effect sizes were used to compare performances between the 3 time points. Results: Reliability of all IMTP variables were very high to nearly perfect (intraclass correlation coefficient [ICC] = 0.86–0.95) between sessions, with acceptable variability (coefficient of variation [CV] = 3.5–8.0%). Furthermore, differences between sessions were trivial (d = 0.002–0.13) and non-significant (p > 0.05). Small to moderate (0.7–2.7%, d = 0.53–0.88) and non-significant (p > 0.05) changes in early isometric force production were observed in response to the moderate intensity training period, while very large (9.2–14.6%, d = 2.71–4.16), significant (p ≤ 0.001) increases in early isometric force production were observed in response to high intensity training, although substantial individual differences can be observed (Figure 1). In contrast, there was a very large, significant increase in peak force (PF) across the moderate intensity training phase (7.7 ± 11.8%, d = 2.02, p = 0.003), but only a moderate and significant, increase in PF (3.8 ± 10.6%, d = 1.16, p = 0.001) across the high intensity phase. Conclusion: The results of this study indicate that high intensity multi-joint resistance training may be superior to moderate intensity resistance training, if the goal is to increase rapid multi-joint force production, while the higher volumes associated with the moderate intensity phase may result in greater improvements in PF. It should be noted that the possible potentiating effect of the moderate intensity phase of training upon the high intensity phase should not be discounted. Practical Applications: High intensity (80–90% 1RM) strength and power training should be performed to enhance rapid force development.

F24
Figure 1.:
Comparison of percentage change in early force production a) force at 50 ms, b) force at 150 ms, c) force 250 ms, between periods of training. ¥ = significant (p ≤ 0.001) increase.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

The Influence of Maturity Status on Force-Time Characteristics During the Isometric Mid-Thigh Pull in Young Male Cricketers

I. Dobbs, M. Wong, I. Moore, J. Oliver, and R. Lloyd

Cardiff Metropolitan University

All technical aspects of cricket performance require high levels of relative strength and power, whether batting, bowling or fielding (1). While mature young athletes are typically stronger than less mature athletes (2), normative data on measures of strength and power currently do not exist for young cricketers of varying maturity status. The isometric mid-thigh pull (IMTP) offers a reliable means of quantifying force-time characteristics in young athletes; however, no studies have explored the force producing capabilities of young cricketers using the IMTP. Purpose: Determine the force-time characteristics during the isometric mid-thigh pull (IMTP) within pre-, circa- and post-PHV male cricket players. Methods: Two hundred nineteen healthy male cricketers, grouped according to estimated maturity status (pre-PHV (G1), n = 123; circa-PHV (G2), n = 62; post-PHV (G3), n = 34), performed 3 repetitions of an IMTP on 2 force plates sampling at 1,000 Hz. Kinetic data from the left and right foot were combined and subsequently the following variables were calculated: absolute peak force (PF), relative peak force (RPF), time to peak force (TPF), rate of force development (RFD), and RFD at 50, 90, 150, 200, and 250 milliseconds. Analysis of variance (ANOVA) was used to determine any significance between groups for IMTP kinematic variables (p < 0.05), followed by Bonferroni post-hoc analysis. Effect sizes were calculated to interpret the magnitude of between-group differences: < 0.20 (trivial), 0.20–0.59 (small), 0.60–1.19 (moderate), >1.20 (large). Results: Absolute PF and peak RFD significantly increased with advancing maturity, G2 was significantly greater than G1 (d = 1.97), while G3 was significantly greater than both G2 (d = 1.67). For relative PF, there were no differences between G2 and G3 (p > 0.05), however, a small (d = 0.37) and moderate (d = 0.65) significant difference existed between G2-G1 and G3-G1 respectively (p < 0.05). For RFD at all time points, moderate to large differences were evident between G2-G1 and G3-G1 (p < 0.001), but no significant differences existed between G2 and G3. No significant differences existed between any of the groups for TPF (p > 0.05). Conclusion: Similar to previous research (3), the relative peak force and rate of force development obtained from the IMTP increased with advancing maturity in young athletes. Increases in force producing qualities via maturation are likely due to natural physical growth in weight as well as the development of neuromuscular properties responsible for force production (4,5). Additionally, no differences between G2 and G3 suggests that additional factors may be more responsible for changes in relative strength in young cricketers. Practical Applications: Practitioners working with young cricketers can use absolute PF and RFD to detect and monitor training-induced changes; however, it may be more prudent to use relative peak force data for talent identification purposes in circa- and post-PHV athletes. Using z scores or percentiles, practitioners can use these normative data for the purposes of bench-marking strength and power in young cricketers.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Relationships Between Jump and Sprint Force-Velocity Profiles and Performance

B. Nicholson,1 B. Jones, A. Dinsdale,2 and K. Till

1Leeds Beckett; and 2Leeds Beckett University

Purpose: The aim of this study was to investigate the associations between matched mechanical variables derived from both vertical and horizontal force-velocity-power (FVP) profiling, and the performance outcome variables within squat jump (SJ) and sprint performance. Methods: Twenty elite academy rugby league players (age 17.6 ± 0.9 years; height 179.9 ± 6.6 cm; body mass 91.2 ± 11.8 kg) performed 2 maximal 40 m sprints. The sprints were recorded using a radar gun device (Stalker ATS II, Applied Concepts, Dallas, TX, USA), which obtained instantaneous speed-time measurements. In addition, the participants performed 2 maximal SJ (∼90° knee angle) repetitions with these loads: 0, 20, 40, 60 and 80 kg. An Optojump (OptoJump Next Microgate, Bolzano, Italy) was used to record the SJ's, which provided jump height (cm) for each load. Body mass relative vertical and horizontal mechanical variables (theoretical maximal values of force (F0) (N/kg), velocity (V0) (m/s), power (Pmax) (W/kg)) and the slope of the F-V linear relationship (Sfv) were calculated. Sprint performance was determined from the modelled velocity-time data (2 m, 5 m, 10 m, 20 m sprint time (s) and Vmax (m/s). Pearson's correlation coefficients (r) assessed the relationship between matched vertical and horizontal mechanical variables (F0 vertical & horizontal, v0 vertical & horizontal, Pmax vertical & horizontal and Sfv vertical & horizontal) and SJ and sprint performance. Results: Table 1 shows the correlations coefficient between the sprint and SJ force-velocity profiles and performance variables. There was no significant correlation between vertical and horizontal FVP matched mechanical variables (p < 0.05). The correlations between vertical FVP variables and sprint performance and between horizontal FVP variables and SJ performance failed to reach statistical significance (p < 0.05). Moderate −0.32 to near perfect 1.0 significant correlations (p < 0.05) were found between mechanical and performance variables shifting the importance of separate variables depending on the testing task. Conclusion: The absence of significant correlations between the vertical and horizontal FVP profiles suggests that they provide distinctive information about the athlete's mechanical variables. The magnitude of the correlations between mechanical variables and sprint performance shifted across the velocity-time curve, therefore performance is determined by separate qualities depending on the distance. Whereas, Pmax reported the greatest correlation with SJ height. Practical Applications: To ensure specific, accurate and comprehensive characterisation of athletes' physical qualities FVP profiles should be determined with exercises maximal mechanically similarity to the targeted performance task. These results will aid practitioners in test selection the prescription and individualisation of training by providing important information as to the most influential variables to develop SJ and sprint performance.

table7
Table 1.:
Pearson's correlations coefficients between the force-velocity relationship parameters (F0, v0, Sfv and Pmax) and performance variables (unloaded squat jump height and sprint performance) obtained during the jumping and sprinting testing.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Do Countermovement Jump Metrics in Male Adolescent Athletes Change During a Competitive Season

F. Jalilvand,1 S. Stecyk,2 P. Marchetti,2 N. Banoocy,3 J. Holt,2 and D. Chapman4

1Granada Hills Charter and California State University, Northridge; 2California State University, Northridge; 3Atlanta United FC; and 4NSW Institute of Sport

Purpose: Strength and conditioning coaches have 2 main goals when training athletes, firstly to improve athletic abilities to reach maximum potential, and secondly to develop specific training protocols that will facilitate appropriate timing of peak performance. Athletes are monitored to provide objective information on the effect of training programs, while assessing the impact of specific training modalities, and to assist with the process of making informed decision regarding program manipulation, all the while informing coaches and or their support staff of the sport needs and maximizing athletic potential. Yet, the goals of training adolescent athletes can be complicated by reduced training opportunities and competitive seasons that are condensed in time due to competing scholastic demands. This study aimed to describe velocity and displacement changes in countermovement jump for young male adolescent basketball players over the course of a condensed competitive season. Methods: Twelve well trained adolescent male basketball players (age: 16.7 ± 1.2 years; weight: 76.6 ± 10.0 kg and height: 183.3 ± 8.9 m) were recruited to participate in this cohort observational research design investigation. The competition was a condensed season played in an eight-week period consisting of 7 home, 3 away, and 3 neutral site games. Players were monitored prior to and following each game of the regular and post season using the countermovement jump (CMJ). Furthermore, twice per week a sessional rating of perceived exertion (RPE) score was given by each player on completion of off-court training to provide a perception of the weeks training physical difficulty. Prior to each testing session, players completed a standardized warm up, consisting of dynamic lower limb stretches, followed by 15 m linear and lateral sprints. A single set of 5 CMJs were performed after the warm up prior to the game and 10 minutes post-game. A portable linear position transducer (PowerTool; Gymaware, Canberra, Australia) and Gymaware propriety cloud software was used for data acquisition and analysis with a displacement based sampling procedure of the data. The linear transducer tether was attached to a lightweight (0.4 kg) dowel, positioned across the athlete's shoulders to remove the effect of arm swing. Variables of interest were jump height (JH), dip displacement (DD), jump height to dip ratio (JH:D), maximal and mean concentric velocity, maximal and mean eccentric velocity. Results: All variables changed significantly (p < 0.001) over the competitive season, with the date of collection explaining 2.75–18.7% of variation in the data. However, no significant interactions for any variable between pre-post game day measures and date of collection were observed. Using pooled data (paired t-test) JH changed significantly (p = 0.017) pre-post with a mean change of 0.39 m (CI: 0.07–0.08), yet DD did not change, resulting in a significant (p = 0.022) pre-post change in JH:D (mean diff 0.023; CI: 0.004–0.042). Athletes mean concentric (p = 0.065) and peak eccentric velocity (p = 0.118) did not change pre-post, however peak concentric velocity did significantly (p = 0.001) decrease. The relative power capacity of the athletes significantly decreased in both mean (p < 0.001, mean diff 1.07 W/kg; CI: 0.75–1.4) and peak (p < 0.001, mean diff 2.32 W/kg; CI: 1.39–3.26). Conclusion: The use of CMJ monitoring with a linear position transducer can highlight the impact that a competitive season has on lower limb performance, providing insightful information on the deleterious changes that competitive matches elicit in adolescent male basketball players. Practical Applications: Continued extended use of similar systematic monitoring in adolescent athletes can provide effective information for improving training strategy. Group response appears to mask individual variation in response to the game stimulus, thus coaches and support staff need to be mindful of providing group strategies and allow for individualized training volumes to sustain higher training loads and elicit greater improvements.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Differences in Power-to-Body Mass Ratios Between Sprint, Middle-Distance, and Distance Swimmers

K. Staab, W. Tramel, K. Lindsay, J. Dawes, and B. Mann

University of Colorado Colorado Springs

The ability to produce power off of either a starting block or wall is essential to maximizing performance in swimmers. Those with increased lower body strength and power have been shown to produce quicker start times. It is important to understand the relationship between relative power in swimmers competing in different events in order to maximize the effects of their training programs. Purpose: This study aimed to compare the mean power-to-body mass (P:BM) ratios between sprint, middle-distance, and distance swimmers. Methods: Archival data were for 45 (21 female, BM: 69.4 ± 6.9 kg; and 24 male, BM: 78.9 ± 6.4 kg) Division I swimmers. Exact ages were unavailable, but as they are NCAA athletes their ages likely ranged between 18 and 25 year old. Peak Power was measured via a series of countermovement vertical jumps (CMJ) on a single axis dual force platform system, sampling at 1,000 Hz. Body mass was collected by the subject standing for 3 seconds with one foot centered on each plate. The subjects remained with their hands on hips and achieved quiet standing for one full second, after which they were instructed to jump as high as possible while keeping their hands on their hips. After landing, the subject returned to the initial starting position. After maintaining a quiet standing position for one second they were instructed to jump again. Each subject was allowed 2 trials and the mean peak power of both trials was utilized to calculate each athletes power to body mass ratio (P: BM) by dividing the absolute peak power on both trials by the athlete's body mass. Results: An analysis of covariance (ANCOVA) revealed no significant differences [F(2, 41) = 0.69, p > 0.05, h2p = 0.01] in P: BM between sprint (n = 8; 56.2 W/kg), middle-distance (n = 32; 49.7 W/kg), and distance (n = 5; 49.5 W/kg) swimmers. Although the purpose of the study was to examine the effect of event on relative peak power, the null hypothesis of the covariate of gender was rejected [F(1, 41) = 63.4, p < 0.001, h2p = 0.6]. Conclusion: No significant differences in P: BM were discovered when comparing sprint, middle distance, and distance swimmers. This may be due to the selection of the CMJ as the measure to determine power output. Practical Applications: Since the use of the stretch-shortening cycle may be limited during swim performance, future studies should consider using a squat jump test to assess power in this population.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Acute Effects of Post-activation Potentiation Using Fast Versus Slow Lifts on Vertical Jump

C. Anthony,1 C. Diehl, C. Blair,1 M. Trevino, J. Volberding,1 D. Smith, L. Brown,2 and T. Baghurst1

1Oklahoma State University; and 2California State University, Fullerton

Previous research supports that weight lifting exercises may induce post-activation potentiation (PAP), thereby enhancing performance of a subsequent biomechanically similar (i.e., explosive) movement. Several studies have utilized a 5RM load to examine the effects of contractile history on vertical jump performance. However, the recovery period or velocity necessary to maximize PAP while minimizing fatigue is unclear. Purpose: Therefore, the purpose of this study was to determine the acute effects of fast and slow velocity lifts using a high-load resistance on the magnitude and time-course of PAP during subsequent maximal countermovement vertical jump (CMVJ) performance. Methods: Eleven male division I collegiate cheerleaders (mean ± SD, age = 20 ± 2 years; height = 176 ± 7 cm; mass 82 ± 10 kg) performed baseline 1RM assessments for the back squat (BS) and hang power clean (HPC). A 5RM (87% 1RM) resistance-load was used in subsequent potentiation (PAP) testing sessions. During each PAP testing session, participants performed baseline CMVJs (pretest) followed by one set of 5 repetitions of the BS or HPC, followed by 7 CMVJs at rest intervals of immediate, 3, 5, 7, 9, 11, and 13 minutes (posttest time points in relation to end of the lift). Results: There was a condition × time interaction. For the BS condition, there were no significant differences in JH compared to baseline (18.71 ± 2.61, p > 0.05), however, JH immediately post-squat was significantly lower (17.49 ± 2.04) than 3 (19.22 ± 2.36, p = 0.002), 5 (19.80 ± 2.30, p < 0.001), 7 (19.40 ± 2.21, p = 0.001), and 9 (18.84 ± 2.44, p = 0.003) minutes post-squat, and 5 minutes post-squat was significantly higher than 11 minutes post-squat (19.80 ± 2.30 vs. 18.16 ± 2.08, p = 0.037). For the HPC condition, there were no significant differences in JH compared to baseline (18.05 ± 2.37) at any time (p = 0.68). Conclusion: This study revealed no potentiation in JH following either slow or fast velocity exercises. This could be due to several PAP factors related to volume, rest time, or exercise selection. Practical Applications: Strength and conditioning specialists looking to enhance vertical jump via a potentiating exercise should consider using either a heavier or lighter load or longer rest intervals. Future research should investigate other exercise velocities and different strength-power trained populations.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Squat Jump Peak Power and Mechanical Work Adaptations Following 10 Weeks of Training With Weightlifting Catching or Pulling Derivatives: Preliminary Findings

S. McKeever,1 P. Comfort,2 J. McMahon, and T. Suchomel1

1Carroll University; and 2University of Salford

Purpose: To examine and compare changes in unloaded and loaded squat jump (SJ) performance that result from training with weightlifting catching and pulling derivatives. A secondary aim was to examine the training effects of using a force and velocity overload stimulus with weightlifting pulling derivatives compared to the traditional loading of weightlifting catching and pulling derivatives. Methods: Twenty-one resistance-trained men were randomly assigned to the catch (CATCH), pull (PULL), or overload (OL) group and completed a 10-week resistance training program. During the training program, the CATCH group performed all weightlifting movements with the catch phase, while the PULL and OL groups performed all weightlifting movements using biomechanically similar pulling derivatives that excluded the catch phase. While the relative intensity of the weightlifting movements of the CATCH and PULL groups was matched, the OL group used heavier loads during the strength-endurance (3 × 10 at 75–85% vs. 55–65% of 1 repetition maximum [1RM] power clean (PC)) and maximal strength (3 × 5 at 90–135% vs. 55–82.5% 1RM PC-exercise specific) phases and a combination of heavier (100–110% vs. 60–75% 1RM PC-exercise specific) and lighter loads (30–45% 1RM PC) during the speed-strength phase (3 × 2–3). Subjects performed unloaded SJ and loaded SJ (body mass +20% of body mass; SJ20) pre-intervention (PRE), mid-intervention 1 (MT1), mid-intervention 2 (MT2), and post-intervention (POST) on force plates. SJ and SJ20 relative peak power (PP) and relative work (RW) were compared between each group. Cohen's d effect sizes were calculated to determine the magnitude of differences in changes between groups; however, no other statistical tests were completed due to preliminary nature of these findings. Results: The mean and standard deviation of each variable from each testing session is displayed in Table 1. The CATCH group displayed trivial changes for all SJ and SJ20 variables. The PULL group displayed trivial-small improvements in SJ-BW PP and RW as well as SJ20 RW; it should be noted that small-moderate improvements in SJ20 PP existed depending on the testing session. The OL group displayed small improvements in SJ and SJ20 PP and RW. Conclusion: The OL group exhibited the greatest SJ and SJ20 improvements compared to the CATCH and PULL groups. In addition, the PULL group demonstrated greater improvements compared to the CATCH group. However, additional data may be needed to confirm these differences given that notable differences in PP and RW existed between the PULL and OL groups during the PRE testing session. Practical Applications: Training with weightlifting pulling derivatives that exclude the catch phase may produce greater PP and RW compared to training with weightlifting catching derivatives. Implementing heavy and supramaximal loads (>1RM PC) that are possible with pulling derivatives may produce greater changes in PP and RW.

table8
Table 1.:
Changes in squat jump relative peak power and work compared to pre-intervention.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Comparison of 2 Alternative Systems for Measuring Vertical Jump Height

S. Staiger and M. Fixen

Dakota State University

Muscular power is an important component of most athletic events. A common procedure to assess lower body power is the standing jump and reach test. However, the traditional standing vertical jump test may not be appropriate for sports like basketball and volleyball. Purpose: To compare 2 different vertical jump measurement devices during an approach vertical jump. Methods: A convenience sample of 37 college students (15 males and 22 females; mean age 20.1 ± 2.1 years), volunteered to participate in this study. The approach vertical jump heights were determined simultaneously by 2 devices (Vertec, and the G-Vert device). The G-Vert device was worn in an elastic belt positioned at waist level during each jump attempt. The subjects completed a brief, dynamic warm-up prior to performing the approach vertical jumps. Each subject was allowed 2 submaximal effort practice jumps prior to performing 5 maximum effort vertical jumps. The subjects were allowed to choose the approach length, however the actual jump required a two-foot take-off. After each jump, both measurements were recorded. Each subject completed a 2nd series of 5 jumps 2–7 days after the first testing session. Vertical jump height was calculated by subtracting reach height from the jump height as measured by the Vertec. The protocol for the 2nd day was exactly the same as the first day. A paired t-test was used to determine differences between vertical jump heights between the 2 measurement devices. Significance was defined as p < 0.05 for all statistical calculations. Results: There was a statistically significant difference in vertical jump heights measured between the 2 devices (Vertec: 20.9 ± 4.9 in.; G-Vert: 21.5 ± 4.4 in.; p < 0.001) Conclusion: Although the results of this study indicated that the G-Vert device recorded average values approximately 0.5 inch higher than the Vertec, the jump heights were basically the same. Practical Applications: Based on these results, either of the devices would provide an adequate measure of an approach vertical jump height. In addition, these devices allow for the ability to assess vertical jump height with sports-related movements.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Countermovement Jump Adaptations Following 10 Weeks of Training With Weightlifting Catching or Pulling Derivatives: Preliminary Findings

T. Suchomel,1 S. McKeever,1 J. McMahon, and P. Comfort2

1Carroll University; and 2University of Salford

Purpose: To examine and compare changes in unloaded and loaded countermovement jump (CMJ) performance that result from training with weightlifting catching and pulling derivatives. A secondary aim was to examine the training effects of using a force and velocity overload stimulus with weightlifting pulling derivatives compared to the traditional loading of weightlifting catching and pulling derivatives. Methods: Twenty-one resistance-trained men were randomly assigned to the catch (CATCH), pull (PULL), or overload group (OL) and completed a 10 weeks training program. During the training program, the CATCH group performed all weightlifting movements with the catch phase, while the PULL and OL groups performed all weightlifting movements using biomechanically similar pulling derivatives that excluded the catch phase. While the relative intensity of the weightlifting movements of the CATCH and PULL groups was matched, the OL group used heavier loads during the strength-endurance (3 × 10 at 75–85% vs. 55–65% of 1 repetition maximum [1RM] power clean [PC]) and maximal strength (3 × 5 at 90–135% vs. 55–82.5% 1RM PC-exercise specific) phases and a combination of heavier (100–110% vs. 60–75% 1RM PC-exercise specific) and lighter loads (30–45% 1RM PC) during the speed-strength phase (3 × 2–3). Subjects performed unloaded CMJ and loaded CMJ (body mass +20% of body mass; CMJ20) pre-intervention (PRE), mid-intervention 1 (MT1), mid-intervention 2 (MT2), and post-intervention (POST) on force plates. CMJ and CMJ20 height (JH), time to takeoff (TTT), modified reactive strength index (RSImod), and relative peak power (PP) were compared between each group. Cohen's d effect sizes were calculated to determine the magnitude of differences in changes between groups; however, no other statistical tests were completed due to preliminary nature of these findings. Results: The mean and standard deviation of each variable from each testing session is displayed in Table 1. The CATCH group displayed trivial changes for all CMJ and CMJ20 variables. The PULL group displayed small-moderate improvements in both CMJ and CMJ20 JH, RSImod, and PP but displayed only trivial changes in TTT. The OL group displayed small improvements in CMJ and CMJ20 JH and RSImod but displayed trivial changes for both TTT and PP. Conclusion: The PULL group exhibited the greatest CMJ and CMJ20 improvements compared to the CATCH and OL groups. In addition, the OL group demonstrated greater improvements compared to the CATCH group. However, additional data may be needed to confirm these differences given that notable differences in JH, RSImod, and PP existed between the PULL and OL groups during the PRE testing session. Practical Applications: Training with submaximal weightlifting pulling derivatives may produce greater CMJ adaptations compared to training with weightlifting catching derivatives or exercise-specific loads for weightlifting pulling derivatives.

table9
Table 1.:
Changes in countermovement jump height, time to takeoff, modified reactive strength index, and relative peak power compared to pre-intervention.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Parameters of the Athlete Triad in Male NCAA Division I Athletes

C. Zajac, J. Moris, B. Selvaraj, A. Frerker, A. Kamp, J. Zuercher, B. Smith, M. Fernandez-del-Valle, and B. Guilford

Southern Illinois University Edwardsville

Purpose: The female athlete triad is defined as having one of the following: low energy availability (EA), abnormal menstrual cycle, or decreased bone mineral density (BMD). Although male athletes are also at risk of developing a similar condition characterized by low BMD, low EA, and reduced reproductive hormones, the triad has not been well studied in male athletes. The purpose of this study was to assess BMD and EA in male NCAA division I athletes participating in a leanness emphasized sport (cross country) and a non-leanness emphasized sport (soccer). We hypothesized that cross country (XC) runners would have both lower BMD and EA compared to soccer players. Methods: Participants included 12 NCAA division I male athletes (20.6 ± 1.4 years) participating in soccer (n = 5) or cross country (XC, n = 7) at Southern Illinois University Edwardsville. Following a 12 hours fast and abstinence from physical activity, a resting metabolic rate (RMR) test, dual energy X-ray absorptiometry scan, and 24-hour food intake recall interview was performed during an early morning testing session. Two unannounced follow-up food intake recall interviews were performed over the phone and used to determine mean daily energy intake. Activity energy expenditure was assessed using an Actigraph activity monitor for 7 days. EA was calculated by subtracting mean daily activity energy expenditure from mean daily energy intake. Low EA was defined as EA < RMR. Group means were compared using an independent samples T-test. Results: XC athletes had significantly lower BMI (20.4 ± 1.0 vs. 25.1 ± 0.9; p < 0.01), total BMD (1.2 ± 0.6 vs. 1.4 ± 0.0 g/cm3; p < 0.05), lumbar spine BMD (1.2 ± 0.7 vs. 1.4 ± 0.1 g/cm3; p < 0.05) and dual femur BMD (1.1 ± 0.0 vs. 1.4 ± 0.0 g/cm3; p < 0.01). In addition, dual femur T-scores (0.6 ± 0.3 vs. 2.3 ± 0.3; p < 0.01) and Z-scores (0.5 ± 0.2 vs. 1.8 ± 0.2; p < 0.01) were lower in XC compared to soccer athletes. There were no significant differences between sports for body fat percentage, total BMD or lumbar spine T and Z scores, RMR, energy intake, activity energy expenditure, or EA. None of the athletes met the American College of Sports Medicine criterion for low total BMD (Z score = ≤ −1.0). Although there were no significant differences in EA between XC and soccer, 20% of XC athletes had low EA whereas 83% of soccer athletes had low EA. Conclusion: In support of our hypothesis, BMD was lower in athletes participating in XC, a leanness emphasized sport, compared to soccer athletes. In contrast, a higher percentage of soccer athletes had low EA compared to XC runners. Only one parameter of the triad must be present to diagnose an athlete with the triad, thus 50% of the athletes in this study exhibited the athlete triad. Practical Applications: Despite the small sample size, these data suggest that male athletes may be at similar risk for the triad as female athletes. Although none of the athletes had low total BMD, chronic low EA can lead to low BMD. It is important to ensure that coaches and athletes are made aware of the risk for the male athlete triad and the potential long term health consequences. In order to thoroughly assess the prevalence of the triad in male athletes, future research that includes a larger and more diverse sample size and reproductive hormone measurements is warranted.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Injury Occurrences With and Without Load Management Strategy in Division II Female Soccer Players

B. Grelle, J. Schneider, A. Anand, M. Wilson, S. Finlay, A. Arenas, W. Brickett, E. De Souza, and J. Andersen

University of Tampa

Load management strategies (LMS) such as manipulation of volume and intensity have been implemented in efforts to reduce injury occurrences (IO) throughout elite sports. Additionally, a LMS is very specific to the sport modality and the performance level of the athlete. It has been suggested that LMS may be a way to reduce injuries and increase performance in Division II (D2) players. However, there is little evidence on LMS in all collegiate sports. Purpose: The purpose of this study was to identify IO with and without a LMS between 2 competitive seasons. Methods: Thirty-four D2 female soccer players (19.76 ± 1.39 years) were observed for muscle strains injuries (MSI), average total distance (TD), and high-speed distance (HSD) (>12.24 km/h) throughout 2017 and 2018 seasons. The athletic training staff was present for all 128 sessions (i.e., 105 training and 23 matches), recorded injuries, and reported MSI. All distances were covered in meters (m) and captured by Global Positioning Satellites and Inertial Movement Units within the 2 years. In the 2017 season, data was only monitored with no implementation of a decision-making strategy based on the data collected. Whereas in 2018, we implemented a LMS that periodized TD and HSD based off of match data within each week. Results: For 2017, the results showed players averaged a TD and HSD per session of 4,684.5 m ± 2,223.3 and 67.3 m ± 132.1, respectively. For 2018, players covered a TD and HSD per session of 5,099.8 m ± 2,339.3 and 690.6 m ± 717.2, respectively. This showed an increase of 8.9% in TD and an increase of 1,026.2% in HSD year over year. Regarding MSI, 13 total IO were reported from 10 different players at the beginning of 2017. In addition, 3 of those same 10 athletes had a reoccurring MSI throughout the season. In 2018, a total 12 IO were reported from 12 different players, with 11 of these being reported at the beginning of the season. Contrary to 2017, only 1 IO was reported later in the season with no recurring injuries. Conclusion: The results suggest that our LMS may have a protective effect on reducing IO throughout the season. However, our findings should be taken with a degree of caution, as in 2018 there was an important increase in HSD (i.e., 1,026.2%) compared to 2017. Therefore, the increase in HSD per session might protect the athletes against MSI. Although it is attractive to suggest that a periodized scheme reduced IO, we can conclude that increasing HSD may moderate the risk for recurrent MSI in Division II female soccer players. Practical Applications: Coaches may utilize LMS by increasing HSD within the week for Division II female soccer players during a competitive season to reduce IO. It is noteworthy to mention that we observed higher occurrences of MSI during the beginning of the season. Furthermore, a player transitioning from pre-season to season may be less prone to injury if HSD are increased from the start of the season.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Association Between Modified Functional Movement Screen Scores and Fear of Falling in Active Older Adults

M. Dietze-Hermosa,1 S. Dorgo, S. Montalvo,2 A. Rodriguez, and I. Jarquin2

1The University of Texas at El Paso; and 2University of Texas at El Paso

Introduction: Older adults are at increased risk of falls and fall-related injuries due to a variety of reasons. These may include decreased motor control, decreased muscular strength or limited mobility. Often older adults develop a fear of falling (FOF), particularly those who have experienced a fall before. Health professionals, including strength and conditioning coaches, seek to establish the best screening processes to identify functional deficiencies that may lead to falls, one of which is the modified Functional Movement Screen (mFMS). Purpose: To examine the association between mFMS scores and FOF in physically active older adults. Methods: One hundred forty-one older adults (56 males and 85 females; mean age ± SD: age 69.51 ± 7.41 years) participated in the study. At the commencement of the testing session subjects completed the modified Falls Efficacy Scale (mFES) questionnaire which aims to assess FOF. The mFES is a 14-activity questionnaire and is scored on a 10-point visual analog scale (1 = not confident; 5 = fairly confident 10 = completely confident). Scores for the 14 questions are then tallied and the average is taken to represent the final score. Following the completion of the questionnaire, the mFMS was administered; mFMS is composed of the following movements: deep squat (DS), shoulder mobility screen (SM), lower body motor control screen (LB-MCS), and active straight leg raise (ASLR). The DS, SM, and ASLR were scored on a 0–3 scale (3 = perfect; 2 = completed with compensation; 1 = unable to complete accurately; 0 = pain), while LB-MCS was scored as a pass or fail. Both the LB-MCS and the SM screen included clearing tests. The clearing tests were scored positive for the presence of pain and negative for the absence of pain. FOF scores for our sample appeared to cluster (min = 8; max = 10) out of the 10-point scale and therefore were treated as categorical and not continuous. Two levels for the mFES variable were created; very high mFES scores (9–10) and high mFES scores (8–9). Scores from the DS, SM, and ASLR were tallied to create a mFMS composite score. The FOF categorical variable and continuous composite mFMS score were analyzed using the Mann-Whitney U test. The categorical FOF and LB-MCS scores were analyzed using the Pearson Chi-Square test. Results: There were no significant differences in composite mFMS scores for individuals who had very high mFES scores (9–10) (mean rank = 72.61) and high scores (8–9) (mean rank = 57.50) (p = 0.17). However, the percent of subjects that passed the right LB-MCS was statistically different for very high mFES scores (57.1%) and high mFES scores (26.7%) (p = 0.03). In contrast, the percent of subjects that passed the left LB-MCS was not different for very high mFES scores (56.3%) and high mFES scores (33.3%) (p = 0.09). Conclusion: There appear to be no differences in composite mFMS scores encompassing the DS, SM and ASLR tests by mFES scores in older active adults. However, LB-MCS scores by mFES scores were statistically different for the right leg. Practical Applications: Increasing mobility, stability and movement proficiency in older adults may counteract FOF and therefore should be emphasized within an exercise program.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

External Loads by Position on NCAA Division II Male Soccer Players

J. Schneider, B. Grelle, S. Finlay, M. Wilson, E. De Souza, and J. Andersen

University of Tampa

Global Positioning Satellites (GPS) and Inertial Movement Units (IMU) allow practitioners and coaches to objectively quantify the external loads placed upon athletes within a soccer match. Additionally, it allows the identification of differences between positional players during those matches. While there is current literature describing external loads in elite soccer players, there is limited research to define external loads in NCAA Division II (D2) male soccer players. Purpose: The purpose of this study was to quantify external loads and present descriptive analysis for each position in D2 male soccer players. Methods: Sixteen D2 male positional soccer players (183.35 ± 6.79 cm; 79.55 ± 6.82 kg) were measured using GPS and IMU during 11 matches for the 2018 competitive season. Players were categorized as defenders (D, n = 6), midfielders (M, n = 4), and forwards (F, n = 6) in this study. Data was monitored and collected for analysis in total distances (TD) and represented in meters (m) from each match. Velocities were defined as: walking (0.36–7.56 km/h), jogging (7.56–13.68 km/h), running (13.68–21.96 km/h), sprinting (>21.96 km/h), and intensity was measured in meterage/minute. Results: Overall, D2 male positional soccer players have a mean TD of 10,876.83 m, walking 4,785.34 m, jogging 3,959.27 m, running 1855.90 m, sprinting 281.94 m, and 98.41m/min. Our results showed there were no significant differences between positions for most of our dependent variables. However, a one-way analysis of variance (ANOVA) revealed that F players accumulated more sprinting distances than other positions (Table 1). Conclusion: The external load results were surprisingly similar between positions in D2 male soccer players. The only significant difference observed was the F for sprinting distances. It should be noted, low sample sizes of matches (n = 11) and players (n = 16) may have skewed the results. Furthermore, a compressed schedule of matches may play a role in different positional distances from previous literature. Practical Applications: Our findings should give coaches a better understanding of external loads at the D2 level of male soccer matches. With this knowledge, practitioners and coaches may observe the positional differences and implement changes in their coaching styles within a competitive season. Additionally, we only observed one coaches playing style leading to our results. It should be noted that a coach's playing style may influence the accumulation of more or less positional distances when comparing matches.

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Thursday, July 11, 2019, 2:00 pm–3:30 pm

Vertical Jump Power Differences in Male and Female High School Athletes Can Be Accounted for by Height and Muscle Mass-Related Variables

M. Shoemaker, Z. Gillen, B. McKay, N. Bohannon, S. Gibson, and J. Cramer

University of Nebraska-Lincoln

Purpose: To examine the sex differences in vertical jump power (VJp, W) and related growth and development variables in high school aged male and female athletes. Methods: Forty-three male (n = 18, age ± standard deviation; 16.6 ± 1.1 years, stature: 176.7 ± 8.1 cm, mass: 71.5 ± 15.1 kg) and female (n = 25, 16.1 ± 1.0 years, 163.2 ± 6.2 cm, 64.0 ± 15.9 kg) high school athletes volunteered for this study. Maturity offset was calculated from height, seated height, weight, and peak height velocity. Fat-free mass (FFM) and percent body fat (BF%) were calculated from skinfolds, while estimated muscle cross-sectional areas (eCSA) were calculated from arm and thigh skinfolds and circumferences. Vertical ground reaction forces were used to calculate peak VJp during counter-movement vertical jumps. Pearson product moment correlation coefficients were calculated among all variables and first-order partial correlations examined collinearity. Unadjusted mean values were compared between sexes with ANOVAs, and adjusted mean values for VJP were compared between sexes with covariates that satisfied the homogeneity of slopes assumption. Results: There were no sex differences for age and weight (p = 0.129–141), but males were greater than females for VJp, height, FFM, arm eCSA, and thigh eCSA (p < 0.001–0.006), and females were greater than males for maturity offset and BF% (p < 0.001–0.001). Homogeneity of slopes across sex existed for height, FFM, thigh eCSA, and arm eCSA (p = 0.110–0.778), and among these variables, sex-specific correlations were found between VJp and height and thigh eCSA (r = 0.442–0.472, p = 0.010–0.012) for males and between VJp and FFM and thigh eCSA (r = 0.595–0.602, p = 0.020–0.031) for females. After partialing out the uninvolved variable, the sex-specific correlations were eliminated (rVJPthigheCSA.height = 0.131, rVJP,height.thigheCSA = 0.313, rVJP,thigheCSA.FFM = 0.309, rVJP,FFM.thigheCSA = 0.243, p = 0.151–0.243). Sex differences for VJP remained different after covarying for height (p = 0.013), height and FFM (0.039), and height and FFM, and thigh eCSA (p = 0.024), but the sex difference for VJp was eliminated after covarying for arm eCSA (p = 0.074). Unadjusted and adjusted means ±95% confidence intervals are displayed in Figure 1. Conclusion: VJP is related to FFM and thigh eCSA in females and height and thigh eCSA in males, but all relationships were eliminated by partial correlations, suggesting significant collinearity. Although males and females were different for VJp, covarying for height, FFM, thigh eCSA, and arm eCSA eliminated these mean differences. Practical Applications: It was possible to eliminate sex-specific differences in VJp in high school male and female athletes by covarying for height and muscle mass-related variables in the present sample. Future studies may consider these variables when trying to reduce the confounding influences of sex for other experimental models.

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Figure 1.:
Vertical Jump Power in male and female high school athletes. This figure displays the unadjusted and adjusted means ±95% confidence intervals for vertical jump power in male and female high school athletes when covarying height and muscle mass-related variables.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Gait Retraining With Real-Time Visual Feedback to Treat Patellofemoral Pain in Adult Recreational Runners

E. Busch, M. Fyock-Martin, N. Cortes, A. Hulse, and J. Martin

George Mason University

Patellofemoral pain (PFP) is a common knee injury in recreational adult runners, possibly caused by faulty mechanics. Current research suggests no definitive gold standard treatment of patellofemoral pain exists. A conservative treatment option of PFP is gait retraining utilizing visual feedback. Purpose: A review was conducted to assess the current evidence on the efficacy of gait retraining using real-time visual feedback to improve pain in adult runners with PFP. Methods: Eight electronic sources were searched using 5 search terms. Studies that met the following criteria were included: (a) utilized gait retraining with visual feedback; (b) participants were adult recreational runners who were diagnosed with PFP; (c) included a minimum of 6 miles (10 km) per week of running; (d) included pain level on the visual analog scale as a pre- and post-intervention measure; (e) included follow up measures of at least one month after intervention. Studies that included participants under 18 and over 45 years of age, and had participants with lower extremity musculoskeletal injuries or other significant health complications were excluded. Results: Three studies were selected based on inclusion and exclusion criteria. A total of 28 participants received gait retraining using real-time visual feedback. The interventions were characterized by 8 sessions over the course of 2 weeks. Feedback to the participants was increased the first 4 sessions, and then progressively decreased the last 4 sessions. The feedback in 2 studies focused on hip and knee alignment, whereas the other study targeted a forefoot strike. Two studies reported a large effect size for knee pain levels of 2.668 (p < 0.001) and 7.61 (p < 0.05), while another study reported a small effect size of 0.294 (p < 0.05). Conclusion: Following strength of recommendation taxonomy (SORT) guidelines, Grade B evidence exists supporting the implementation of gait retraining with real-time visual feedback as a means of treating adult runners diagnosed with PFP. The findings were inconsistent and this may be due to differences in methodologies. Practical Applications: Practitioners working with runners who have PFP may try implementing a real-time visual feedback gait retraining program to reduce knee pain. Research suggests that feedback should be focused on hip and knee mechanics.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

NBA Draft Combine Trends and Comparisons With Division I NCAA Mid-Major Players: A Longitudinal Approach to Analyzing Important Physiological and Performance Characteristics

A. Beljic,1 I. Salazar,2 and R. Lockie3

1California State University Fullerton; 2California State University, Fullerton Athletics; and 3California State University, Fullerton

Introduction: The National Basketball Association (NBA) Combine is a multi-day showcase event for basketball players that takes place a month before the draft to help scouts and teams compare the abilities of different players. A large part of the combine is anthropometric and physical fitness testing. For players from smaller schools that may not be as heavily scouted, it is important to ascertain whether they should strive for certain characteristics comparable to players featured at the combine. Strength coaches should know whether they are developing the most important characteristics in their players, and whether these are historically important. Purpose: To determine whether there are trends in the last 10 years of NBA Combine testing, and how mid-major Division I (DI) players compare to these standards. Methods: A successful (NCAA 2018 Tournament Bid) mid-major DI team completed the NBA Combine tests, including: body mass, height, standing reach, and wingspan; maximum repetitions of a 84-kg bench press; ¾ court sprint; and a countermovement jump (CMJ) as well as a 4.6 m (15 ft) approach jump (AJ). NBA Combine data for the years of 2018, 2013 & 2008 was collected through the official NBA website. Data was divided into 2 groups: backcourt and frontcourt players. A one-way ANOVA with a Bonferroni post-hoc test (p < 0.05) was performed to determine whether any differences in means occurred between the 2018, 2013 and 2008 draft classes to establish any historical trends. Independent samples t-tests (p < 0.05) were used to compare the 2018 draft class with the mid-major players. Results: There were significant interactions between the draft classes in the ¾ court sprint for both the back court (F(2,88) = 12.191, p < 0.01) and frontcourt (F(2,61) = 7.244, p < 0.01) groups, and the AJ for the backcourt (F(2,88) = 3.394, p < 0.04) and frontcourt (F(2,61) = 3.753, p < 0.03) groups. Post-hoc tests analyses showed that there is no trend in the ¾ court sprint as 2013 was an outlier year (p < 0.01). However, AJ was significantly lower in 2008 compared to 2013 and 2018 (∼4–6 cm; p < 0.01). When comparing the 2018 Draft Combine and mid-major group there was a significant difference in favor of the combine players compared to both frontcourt and backcourt groups in terms of wingspan (p ≤ 0.001) and reach (p = 0.003 and 0.007, respectively), and body mass for the backcourt group (p = 0.002). The DI frontcourt players had lesser performance in the ¾ court sprint (p = 0.018) and AJ (p = 0.020) compared to the combine players. Conclusion: In terms of future trends, the physiological profile of a potential NBA player remained steady, although the increase in the AJ is worth noting. Through the mid-major player comparisons, the data supported assumptions that even though players at a mid-major level college may have similar performance qualities relative to combine players, longer players (as measured by reach and arm span) may receive more opportunities via NBA Combine invitations. Additionally, the differences between the ¾ sprint and AJ for the frontcourt players may reflect the relative scarcity of athletic frontcourt male players available at the mid-major level. Practical Applications: In terms of their physiological profile on draft day, mid-major level college players who do not satisfy the anthropometric standards for their position should consider excelling at performance characteristics in order garner attention from NBA scouts and coaches.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Anthropometric Measurements as Indicators of Performance on High-Intensity Functional Training Workouts

L. Wolff,1 R. Svean,2 R. Pettitt, A. Aguinaldo, and J. Dexheimer

1Azusa Pacific University; and 2Point Loma Nazarene University

Introduction: High Intensity Functional Training (HIFT) pushes the boundaries of overall fitness through a wide variety of movements and workouts. Some investigations have explored the relationship between physiological variables and HIFT performance, however anthropometric measurements have been overlooked. Longer lower limbs and lower body fat result in improved running performance, while higher fat free mass demonstrates increased strength and force production. The variety of movements involved in HIFT including metabolic conditioning, weightlifting, and gymnastic movements necessitate further investigation into the influence of anthropometrics on HIFT performance. Purpose: The purpose of this study was to examine which anthropometric measurements best predict performance of HIFT workouts. Methods: 31 functionally trained participants (Age: 29 ± 5 years; Height: 69.3 ± 6.3 in; Weight: 80.9 ± 15.1 kg; Experience: 42.4 ± 28.3 months) performed 4 workouts. Workout 1 consisted of 3 rounds of 21-15-9 reps of thrusters and pull-ups (95 lb men/65 lb women). Workout 2 consisted of 30 clean and jerks (135 lb men/95 lb women). Workout 3 consisted of 5 rounds of a 400 m run and 15 overhead squats with a barbell (95 lb men/65 lb women). Workout 4 consisted of performing a 1RM of a back squat, shoulder press, and deadlift. Anthropometric measurements of upper and lower limb length were recorded as well as body composition. Upper limb length was measured as wingspan, while lower limb length was measured as the length from the anterior superior iliac spine to the medial malleolus. Body composition was measured using air displacement plethysmography to obtain measurements of fat mass, fat free mass, and % body fat. A Pearson's r test was performed to determine the relationship between anthropometric variables and workout performance. For each HIFT workout dependent variable, a stepwise multiple linear regression was created using significant correlative data. Data are reported as means and standard deviations with the alpha level set a priori at 0.05. Results: For Workout 1 (288.3 ± 95.8 seconds), lower limb length (34.6 ± 2.6 in) and fat free mass (66.6 ± 13.3 kg) explained 53.6% of the variance, F (2,28) = 16.19, p < 0.001. The measures of fat free mass (β = −1.318, p < 0.001) and lower limb length (β = 0.818, p = 0.004) were statistically significant. For Workout 2 (192.1 ± 85.7 seconds), fat free mass explained 46.1% of the variance, F(1,29) = 24.791, p < 0.001. This was the only statistically significant variable (β = −0.679, p < 0.01). For Workout 3 (901.6 ± 150.7 seconds), fat free mass explained 29.6% of the variance, F(1,29) = 12.179, p = 0.002. This was the only statistically significant variable (β = −0.544, p = 0.002). For Workout 4 (363.5 ± 97.7 kg), fat free mass and lower limb length explained 85.9% of the variance, F(2,28) = 85.6, p < 0.001. Fat free mass (β = 1.224, p < 0.001) and lower limb length (β = −0.363, p = 0.016) were the only statistically significant measures. Conclusion: In conclusion, fat free mass and longer lower limb length are both indicators of HIFT performance. Practical Applications: Though lower limb length cannot be modified, exercise programming aimed at inducing hypertrophy may improve HIFT performance.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Changes in Size and Physical Performance in the NFL Scouting Combine From 2006–2008 to 2016–2018

J. Kurcoba,1 M. Norford,2 D. Church,3 and K. Beyer1

1Bloomsburg University; 2Applied Body Science; and 3University of Arkansas for Medical Sciences

Purpose: To assess the changes in size and physical performance in athletes at the National Football League (NFL) Scouting Combine from 2006–2008 to 2016–2018. Methods: Data for the 1,786 athletes who participated in the NFL Scouting Combine from 2006 to 2008 and 2016 to 2018 were obtained. Athletes were grouped according to their position at the NFL Scouting Combine into offensive line (OL), defensive line (DL), running back (RB), tight end (TE), linebacker (LB), wide receiver (WR), and defensive back (DB). Athletes not included in one of these categories were excluded from the analysis. Data was collected from each athlete for height (HT), body mass (BM), vertical jump (VJ), 40-yard dash time (40T), bench press repetitions (BP), broad jump (BJ), L-drill time (LD), and pro-agility time (PA) of athletes. Difference in variables over the 10-year time period were analyzed using independent samples t-test for each position. Data reported are mean difference ± standard error of difference. Alpha level was set a priori to p ≤ 0.05. Results: DB displayed significant increases in HT (p < 0.001, 1.65 ± 0.43 cm) and BJ (p = 0.019, 4.06 ± 1.71 cm), with significant decreases in BP (p = 0.009, −1.16 ± 0.44 reps), LD (p = 0.003, −0.09 ± 0.03 s), PA (p = 0.019, −0.05 ± 0.02 s), and a negative trend in BM (p = 0.075, −0.97 ± 0.54 kg). DL displayed a significant decrease in BP (p = 0.035, −1.54 ± 0.72 reps) and a positive trend in HT (p = 0.093, 0.76 ± 0.45 cm). LB displayed significant increases in HT (p = 0.001, 1.76 ± 0.50 cm) and BJ (p < 0.001, 8.56 ± 2.04 cm), and a positive trend in BM (p = 0.074, 0.93 ± 0.52 kg), with significant decreases in BP (p = 0.001, −1.98 ± 0.60 reps) and LD (p = 0.040, −0.07 ± 0.03 s). OL displayed a significant decrease in BP (p = 0.007, −1.72 ± 0.63 reps). RB displayed a significant decrease in BP (p < 0.001, −2.94 ± 0.80 reps) but a significant increase in BJ (p = 0.019, 6.14 ± 2.60 cm) with a positive trend in HT (p = 0.065, 1.23 ± 0.66 cm). TE displayed significant decreases in BM (p = 0.015, −1.94 ± 0.78 kg) and BP (p = 0.003, −2.53 ± 0.82 reps), but a significant increase in BJ (p = 0.001, 12.23 ± 3.43 cm). WR displayed a significant decrease in BP (p < 0.001, −3.07 ± 0.63 reps), but displayed positive trends for 40T (p = 0.061, 0.02 ± 0.01 seconds) and BJ (p = 0.064, 3.36 ± 1.81 cm). Conclusion: Most performance changes over the 10 years varied depending on position, but all positions displayed a decrease in BP performance. BJ was improved across most positions. Both 40T and VJ remained relatively unchanged since 2006–2008. DL and OL had no improvements in any performance test, which may indicate a lack of applicability of the tests to the demands of these positions. Practical Applications: These changes in size and performance may indicate the perceived importance of certain performance tests during the NFL Scouting Combine, specifically an increased focus on BJ. Strength and conditioning coaches can use this information to ensure that an athlete's training is tailored to meet the current demands for each position. This will allow the athlete to showcase their abilities at future NFL Scouting Combines and stand out amongst other prospects.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

The Influence of Player Position on Match Play Loading in Elite Female Soccer Players

E. Rogers and N. Jenkins

Oklahoma State University

Purpose: This study aimed to examine the influence of player position on match play loading, determined by GPS and accelerometer data, in a team of elite female soccer players in Northern Ireland. Methods: Players (n = 16) were divided into 3 positional groups: defenders (n = 6, obs = 12), midfielders (n = 8, obs = 18) and forwards (n = 3, obs = 6) and data was gathered over 5 matches. Total distance (TD), average and max speeds (AS and MS), accelerations and decelerations (ACC and DEC), high-speed running distance (HSRD), sprint distance and count (SD and SC), dynamic stress load (DSL), total load (TL), explosive distance (ED), high metabolic load distance (HMLD) and equivalent metabolic distance (EMD) data were used for analysis. Results: Midfielders and forwards covered a significantly greater TD than defenders (+14%, p < 0.001 and +13%, p = 0.006, respectively), recorded more SC (+41%, p = 0.036 and +76%, p = 0.003, respectively), and covered significantly greater SD (+57%, p = 0.020 and +102%, p = 0.002 respectively) than did defenders. Midfielders and forwards covered significantly more HSRD than defenders (+31%, p = 0.025 and +39%, 0.0125, respectively). Midfielders and forwards also had significantly faster average speeds than defenders (+14%, p = 0.020 and +15%, p = 0.002, respectively) and forwards had significantly faster max speeds than defenders (+56%, p = 0.014). Midfielders and forwards performed significantly more ACC than defenders (+38%, p = 0.005 and 4 + 8%, p = 0.009, respectively) and forwards performed significantly more DEC than defenders (+48%, p = 0.028). Midfielders and forwards covered greater HMLDs than defenders (+34%, p < 0.016, and +61%, p = 0.001, respectively), and they also presented with significantly higher EMD values than defenders (+15%, p < 0.001 and +17%, p < 0.001, respectively). In contrast, there were no significant differences observed between any positional groups for DSL, TL, or ED (Table 1—Descriptive Statistics). Conclusion: It is clear that elite soccer forwards and midfielders have similar workloads, which are greater than for defenders during match-play. Practical Applications: The results of this study may provide coaches with information regarding positional differences in the physiological demands of soccer during match play. These differences should be taken into consideration when designing and implementing training plans.

table10
Table 1.:
Descriptive Statistics.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Relationship Between Running Performance and Perceived Stress and Recovery in Division I Male Collegiate Soccer Players

S. Rossi, M. Eisenman, and G. Ryan

Georgia Southern University

The collegiate soccer season requires athletes to participate in daily training prior to and immediately after weekly competitive matches. It is important that these athletes are able to recover mentally and physically during weekly training to prevent injuries, mental fatigue, and potential overtraining during the competitive season. Coaches and training staffs oftentimes look for quick, practical low-cost methods of determining the readiness of their players prior to training, and the perceived intensity of the session post-training. Purpose: The intent of the present study was to examine the relationship between rating of perceived exertion (RPE) and perceived recovery score (PRS) with distance traveled (D) and maximum speed (Smax) obtained during training. Methods: Twenty-six Division I male soccer players volunteered to wear a bio-harness during each in-season training session. The bio-harness continuously collected D and Smax for each participant throughout the course of each training session. Prior to each practice, participants reported their PRS leading into training. Immediately following practice, participants reported a training session RPE. A total of 41 practices were included for analysis. Data was uploaded post practice onto a computer for analyzation. Due to the categorical nature of the scales, Spearman-rho correlations were run to determine the relationship between self-reported PRS and RPE and D and Smax. Significance of relationships was set a p = 0.05. Results: A significant (p < 0.01), moderate (r = 0.44), positive relationship was shown between RPE and Smax. Additionally, a significant (p < 0.01), strong (r = 0.69), positive relationship was shown between RPE and D. No significant relationships were present between PRS and either Smax (p = 0.99, r = 0.00) or D (p = 0.36, r = 0.03). Conclusion: These data indicate that pre-training, self-reported perceived recovery scores did not have an impact on the amount or intensity of running performed during training throughout the course of a competitive season. Post-training, self-reported perceived exertion was influenced, fairly strongly, by both quantity and intensity of running during training sessions. Practical Applications: Athlete self-reported RPE continues to be a practical tool for coaches, training staffs, and athletes to use to gain insight into both the amount and intensity of running during training. While monitoring perceived recovery is an important consideration for coaches and training staffs to determine overall readiness of their athletes during a competitive season, PRS, by itself, does not seem to be an indicator of the quantity or intensity of running that an athlete is able to perform during training.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Fast Velocity Eccentric Cycling Causes Greater Muscle Damage Than Slow Velocity Eccentric Cycling

H. Ueda,1 Y. Tsuchiya, and E. Ochi2

1Teikyo Heisei University; and 2Hosei University

Repeated eccentric cycling exercises cause in increases in muscular size and strength at low energy demand than concentric cycling training. On the other hand, it is widely known that excessive eccentric exercise may cause muscle damage. Muscle damage following eccentric exercise is characterized by loss of muscle strength, limited range of motion (ROM) and development of delayed onset muscle soreness (DOMS). Interestingly, previous study suggested that, for the same time under tension, fast velocity eccentric exercise of elbow flexors causes greater muscle damage than slow velocity. However, the effects of contraction velocities on the magnitude of muscle damage after eccentric cycling exercise are still unclear. Purpose: The purpose of this study was to compared maximal fast velocity eccentric cycling and slow velocity eccentric cycling for magnitude of muscle damage before, immediately, and 4 days after exercise. Methods: Twelve untrained men participated in this study. The subjects performed 2 modes of isokinetic eccentric cycling to a bilateral leg at random. The velocities of eccentric cycling were either 30 deg/sec (SLOW) or 210 deg/sec (FAST) each 5 minutes by a cycle ergometer. Changes in maximal isokinetic torque (30 and 210 deg/sec), ROM, and DOMS were assessed before, immediately, 1, and 4 days after exercise. Results: Although the peak torque during cycling was no significant difference between SLOW and FAST, the work output during cycling for FAST was higher than that for SLOW (p < 0.05). Compared with the pre-exercise value, maximal isokinetic torque at both 30 and 210 deg/sec for FAST had significantly decreased immediately after exercise, and this tendency continued until 4 days (p < 0.05). However, no significant differences in maximal isokinetic torque for SLOW were observed at all time points after exercise. The maximal isokinetic torque at 30 and 210 deg/sec had significantly decreased in the FAST than in the SLOW at immediately after exercise, and remained until 4 days. A significant level of DOMS in vastus lateralis, rectus femoris and vastus medialis were indicated by FAST compared with pre-treatment value (days 1 and 4; p < 0.05). Significantly greater DOMS for vastus lateralis was observed in the FAST compared with the SLOW at the only 4 days after exercise. No significant difference in the ROM from the pre-exercise values or between SLOW and FAST were observed at any time points. Conclusion: This study showed that fast velocity eccentric cycling causes greater muscle damage than slow velocity eccentric cycling in untrained subjects. Practical Applications: These findings of this study could be useful information for creating protocols of the eccentric cycling training program. In the future, it is necessary to investigate the effect of long-term training of eccentric cycling with different contraction velocities on muscular strength and hypertrophy.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Athletic Performance Apparel User Experience: An Exploratory Study

T. Cieslak, C. Almanza, and A. Simpson

Florida International University

The information era has given birth to a new breed of sport & exercise management, which uses new technologies (e.g., performance apparel, wearable devices, data analytics) to improve athlete performance. Previous studies have established an individual adopts new technologies in 4 phases: Anticipation, Orientation, Incorporation and Identification. Additionally, these studies noted the most critical stages for behavioral change are Anticipation and Orientation, which are characterized by fulfilling user expectations and helping users improve their performance, reduce injury and facilitate recovery, respectively. To date, most studies have examined the effectiveness of athletic performance apparel (APA). However, there is minimal information available to strength & conditioning (S&C) coaches describing or quantifying athletes' expectations and experiences with APA. Purpose: To understand “how” athletes learn to use new technologies. In specific, the objectives of our study were to examine the relationships between APA use and influence on 1) self-reported TTM (Transtheoretical Model) physical activity stage; 2) outcome expectations (OE) motives; and 3) user experience (UX) factors. Methods: A PreTest-PostTest protocol established TTM stage and examined expectations while a 9-week Time-Series design recorded UX of 20 healthy male, recreational athletes (Mean ± SD; Age: 20.8 ± 1.8 years; Height: 180.2 ± 4.0 cm; Mass: 74.5 ± 3.6 kg; Vo2max: ≥ 50 ml/kg/min) with updated versions of the TTM and OEE instruments and an adopted UX questionnaire, respectively. Each participant, recruited from a local running club, completed identical experimental testing before and after a 9-week S&C program designed to establish a baseline of fitness (Weeks 1–4; Overload Training) and maximize use of compression gear while preparing for a half marathon (Weeks 5–9; Specificity Training). Results: Pre-Test data indicate that participants were evenly distributed across the 6 TTM stages while Post-Test data illustrate a positive change in physical activity (Preparation, n = 2; Action, n = 8; Maintenance, n = 6; Excel, n = 4). Results indicate that participants had “moderate” outcome expectations during the Anticipation phase and these expectations being fulfilled during the Incorporation phase for Physical Performance (OE-PP; 3.67 ± 0.40), Psychological Impact (OE-PI; 3.31 ± 0.44) and Social Status (OE-SS; 2.94 ± 1.03). Also, the data indicate a positive significance difference (p < 0.05) and negative significance difference (p < 0.05) for OE-CAR (1.96 ± 0.80). The UX data illustrate positive trends, from Week 1 to Week 9, with 90% of participants agreeing APA improves performance and aids recovery. Additionally, 80% of participants said they would continue using the APA after the project. Conclusion: The results suggest that APA users experienced 1) a positive change in physical activity, 2) fulfilled expectations and 3) “how” to use APA to improve performance and recovery. Thus, 16 participants finished the project in the Identification phase. Practical Applications: It is recommended both sport managers and S&C coaches use APA, such as compression gear, due to its cost effectiveness and ease of use. Additionally, because research supports its effectiveness (e.g., improved blood flow, decreased muscle vibration, increased proprioception, reduced muscle soreness), APA would be a useful tool for both coach and athlete.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Sex Differences in Muscular Fitness Abilities of Obese Latino Children Is a Not Result of Fat Free Mass

E. Perez, J. Merrigan, A. McKay, L. Biscardi, S. Gallo, J. Fields, R. Mehlenbeck, and M. Jones

George Mason University

Sex, low income, insufficient physical activity levels, and excess body fat have been associated with low physical fitness levels in children. Further, children of Latino descent are more likely to be obese than their white counterparts. Yet, little is known about fitness abilities of obese, Latino children. Purpose: To evaluate the relationship between fitness tests and body fatness, as well as potential sex differences in the physical fitness capabilities of obese boys and girls of Latino descent and low socio-economic status. Methods: Sixty children (boys, n = 39, 7.8 ± 1.54 years; girls, n = 21, 7.2 ± 1.5 years), who were in the 97.8 ± 2.5th percentile for age- and sex-based body mass index (BMI), completed a battery of fitness tests. Morning assessments of height, weight, body fat (bioelectrical impedance analysis), and socio-economic status were completed prior to all fitness tests. Fitness assessments were administered in the following order: handgrip strength (HG), seated medicine ball throw (SMBT), shuttle run (SR), vertical jump (VJ), and standing long jump (SLJ). Three repetitions of each test were completed and one minute of rest was allotted between attempts. The maximal value achieved for each test was used for analysis. Correlations were used to determine relationships between fitness tests and body fatness (weak, r = 0.20–0.39; moderate, r = 0.40–0.59; strong, r = 0.60–0.79). Independent samples t-tests were run to determine differences between boys and girls. Alpha level was set to 0.05. Results: Body fat percentage was negatively related to vertical jump height (r = −0.483, p < 0.001) and SLJ distance (r = −0.310, p = 0.016) and positively related to SR time (r = 0.370, p = 0.004) and SMBT distance (r = 0.255, p = 0.049). Boys had greater SLJ distance (t(58) = 2.208, p = 0.031), faster SR times (t(58) = −2.457, p = 0.017), and greater SMBT (t(58) = 3.839, p < 0.001) than girls. No difference in body fat percentage existed between boys and girls (t(58) = 0.170, p = 0.866). After accounting for fat free mass, boys performances remained greater on the SLJ (mean difference, 0.42 m; CI 95%, 0.001, 0.845; p = 0.049), SR (mean difference, −0.044 seconds; CI 95%, −0.0803, −0.0074; p = 0.019), SMBT (mean difference, 1.485 m, CI 95%, 0.633, 2.337; p < 0.001). Conclusion: The relationships between body fat percentage and fitness tests reinforce previous findings that obese children have increased difficulty performing motor tasks that include carrying of bodyweight, but may excel in motor tasks that do not. In support of previous findings, boys in the current study had preeminent performances in the SLJ, SR, and SMBT compared to girls. These differences remained apparent even after controlling for fat free mass, suggesting potential motor skill deficits. Practical Applications: Inclusion of musculoskeletal exercises and high intensity activities may help improve motor skill competence and thus, may be beneficial for young, obese, Latino girls.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Negative Mood State Predicts External Load in a NCAA Division I Men Soccer Pre-season

J. Fields, D. Lameira, J. Short, J. Merrigan, L. Biscardi, J. White, and M. Jones

George Mason University

Monitoring the training load in soccer is a key component of the training process as it helps set an adequate balance between training and recovery. It is well known that psychological factors can affect performance. Specifically, mood may be altered in response to increased training loads, which increases depression, anger, fatigue, and tension. An increase in these negative mood states has been associated with reduced performance and heightened risk of injury. Further, the evaluation of mood states may help prevent and identify possible non-functional overreaching and overtraining conditions. The pre-season phase is of particular concern because training loads are often 2–4x greater than in-season, and monitoring mood may provide insight into training responses. Purpose: To investigate the relationship between negative mood states and external load markers during a collegiate men's soccer pre-season. Methods: National Collegiate Athletic Association (NCAA) Division I soccer athletes (n = 20; mean age: 20.3 ± 0.9 years; body mass: 77.9 ± 6.8 kg; body height: 178.87 ± 7.18 cm; body fat: 10.0 ± 5.0%; Vo2max: 65.39 ± 7.61 ml·kg−1·min−1) participated. The Brief Assessment of Mood (BAM) was collected daily to assess self-reported levels of tension, anger, depression, fatigue, and confusion. Total distance (TD), player load (PL), high-speed distance (HSD, >13.5 mph), high inertial movement analysis (IMA, >3.5 m/s2), and repeated high intensity efforts (RHIE) were collected in each training session using GPS/GNSS technology. Multilevel models assessed the bi-directional prediction of negative mood on external load markers. P < 0.05. Results: A negative mood measure including tension, fatigue, anger, depression, and confusion items was created from the 6-item BAM (excluding the vigor item) and found to be reliable (r = 0.716). Morning ratings of negative mood were positively predicted by previous day's afternoon practice HSD (p = 0.009). Neither TD nor PL affected next day's ratings of negative mood. Additionally, negative morning mood states inversely predicted HSD (p = 0.011), TD (p = 0.002), and PL (p < 0.001) for that day's afternoon practice. IMA and RHIE had no relationship with negative mood states. Conclusion: HSD was the only measure to positively predict next day's negative mood. However, negative mood inversely predicted HSD, TD, and PL for that day's practice. Practical Applications: Athletes who have higher negative mood states most likely experience a reduced performance in practice. High intensity sessions may adversely affect athletes' mood the following morning, which in turn may negatively impact both volume and intensity measures during the subsequent training session. Because negative mood is highly related to performance and also acts as an indicator of overtraining status, practitioners may wish to use the BAM as a quick and easy assessment. Utilizing self-assessment mood scales with positional monitoring technology may enhance the understanding of training responses and inform training program development.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Measurement Invariance of a Latent Model of Child Physical Activity Based on Child and Parent Surveys and Wearable Physical Activity Tracker Data

A. Miramonti1, J. Bovaird1, M. Krehbiel1, and L. Franzen-Castle2

1University of Nebraska—Lincoln; and 2University of Nebraska-Lincoln

Physical activity (PA) behavior is notoriously difficult to assess accurately in free-living populations, particularly children. Data from self-report (SR) measures in children often have limited reliability and parent-reported (PR) measures tend to overestimate PA levels, particularly for children who do not meet PA guidelines. While wearable PA trackers (WT) are not a gold-standard measure of PA, they often provide data with better reliability and validity than data from SR or PR measures. Consumer WTs have become less expensive and more feasible for research and program evaluation but are still subject to sources of error that can be difficult to control in free-living contexts. It may be possible to model the child's physical activity (CPA) as a latent construct (an unobservable or abstract concept) where the outcomes obtained from SR, PR, and WT measures are considered manifest indicators. Latent variable modeling reduces the effects of unreliability and permits the inclusion of incomplete cases. However, to draw meaningful conclusions from the model regarding changes in PA behavior or differences between groups, measurement invariance must be established. Purpose: To model child's physical activity as a latent construct using self-report, parent-report, and wearable fitness tracker data and to assess the model for longitudinal and between-group measurement invariance. Methods: At the beginning and end of a 12-week afterschool PA and nutrition program 126 fourth-fifth grade participants completed surveys (including demographic, self-reported PA, and PA self-efficacy items) and wore PA trackers for 7 days; 103 parents completed surveys (containing demographic and PA and sedentary behavior frequency items). A configural model was assessed for model fit and then used as the baseline for comparison for longitudinal invariance testing (Δχ2 tests); the final longitudinal model including latent means (Model 4) was used as the baseline for comparison for between-group invariance testing for binary indicators based on grade (5 TH), gender (FEM), weight status (WS), minority status (MIN), socioeconomic status (SES), and season (FALL). Results: The configural model (Table 1, Model 1) adequately reproduced the sample covariance matrix (χ2(29) = 40.2, p = 0.08). Δχ2 tests show that the model exhibited metric, intercept, and between-group measurement invariance (Table 1, Models 2–10). Conclusion: These results demonstrate that the CPA model exhibits both longitudinal and between-group measurement invariance and meaningful inferences can be made regarding changes over time or differences between groups. Further research will determine whether this latent model exhibits construct validity. Practical Applications: A latent variable model of child physical activity behavior based on a combination of self-report, parent-report, and wearable physical activity tracker data may be a useful assessment tool for research and program evaluation.

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Thursday, July 11, 2019, 2:00 pm–3:30 pm

Correlation Between Performance in the Special-Judo-Fitness-Test and Physical Fitness Measurements

J. Roman,1 L. Martinez,2 and C. Nevarez3

1Tasis Dorado; 2University of Puerto Rico, Rio Piedras Campus; and 3University of Puerto Rico, Medical Sciences Campus

Judo is an Olympic sport with high physiological demands and the requirement of specialized technical skills. The Special Judo Fitness Test (SJFT) proposed by Sterkowicz (1995) combines technical skills and physical demands and has been widely used as a specific test to evaluate the athlete's performance. Purpose: To assess the relationship between physical fitness measurements and performance in the SJFT (total throws and index) in college judokas. Methods: Thirty-one healthy college judokas participated in this study: 19 males (Mean ± SD; Age: 20.47 ± 2.3 years; Height: 173.24 ± 6 cm; Mass: 75.12 ± 9.8 kg) and 12 females (Mean ± SD; Age: 20.4 ± 1.4 years; Height: 157.1 ± 7 cm; Mass: 58.4 ± 7 kg). Physical fitness evaluations included: anthropometric restricted profile (ISAK), treadmill graded exercise test to maximum (Vo2 max), squat and counter movement jump in a contact platform (A2 Bosco), isometric hand grip strength and a 3–6 repetition maximum (RM) bench press and half squat test with free weights and a linear transductor encoder. Participants also performed the SJFT. Pearson product-moment correlations were used to asses relationships between SJFT and fitness evaluations. Results: Body fat (Mean ± SD) was 12.4 ± 5.0 in males and 23.4 ± 3.5% in females. Relative Vo2max (ml/kg/min) was 50.84 ± 4.0 in males and 41.41 ± 3.5 in females. 1-RM bench press relative to body mass was 1.17 ± 0.12 in males and 0.81 ± 0.18 in females, while 1-RM half-squat relative to body mass was 1.63 ± 0.30 and 1.35 ± 0.22 for males and females, respectively. Combined right and left isometric handgrip strength was 98.44 ± 11.9 and 64.17 ± 10.9 kgs in males and females, respectively. Lower body power production (Watts) in males was 3,573.53 ± 514.47 in squat jump and 3,789.65 ± 549.79 in countermovement jump, while females' power was 2,088.58 ± 389.86 and 2,250.92 ± 398.83 Watts in squat and countermovement jump, respectively. Total throws in the SJFT was 25.53 ± 1.63 for males and 22.75 ± 1.87 for females, while the SJFT index was 13.93 ± 1.03 and 15.28 ± 1.30 for males and females, respectively. Significant strong correlations were found between total throws in the SJFT and Vo2 max (r = 0.683), relative 1-RM bench press (r = 0.617), handgrip isometric strength (r = 0.637), squat jump (r = 0.629) and countermovement jump (r = 0.652). An inverse correlation was found between SJFT total throws and % body fat (r = −0.613) (p < 0.01). Significant moderate and strong correlations were found between the SJFT index and Vo2max (r = −0.655), relative 1-RM bench press (r = −0.498), handgrip isometric strength (r = −0.469), squat jump (r = −0.467) and countermovement jump (r = −0.497), and a direct correlation with % body fat (r = 0.480) (p < 0.05). Conclusion: The results of this study denote that moderate to strong positive relationships exist between cardiorespiratory endurance, dynamic upper body strength, isometric handgrip strength, lower body power, body composition and performance measures of the SJFT. These relationships are stronger for total throws than for the SJFT index, except for Vo2max which correlates strong with both. Practical Applications: Since it has been demonstrated that performance in the SJFT differentiate between competitive levels in the sport of judo, this study supports the importance of developing these fitness characteristics in preparation for high level competition.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Effects of a Combined Aerobic and Resistance In-School Training Program in Adolescent Females

J. Carreño,1 J. Otero, S. Rueda,2 P. Lopez, P. Camacho,3 and D. Cohen4

1Universidad de Santander; 2Universidad Autonoma de Bucaramanga; 3Clinica Foscal; and 4Universidad de Santander

In youth, muscular strength, aerobic fitness, and body composition are independently associated with cardiometabolic health and are all influenced by physical activity patterns. Declines in physical activity during adolescence, more pronounced in females, are of public health concern and the impact of exercise interventions aimed at engaging this population of interest. Purpose: To determine the effects of a combined aerobic and resistance training in-school intervention on muscular and aerobic fitness, and body composition in adolescent girls. Methods: One hundred twenty-one girls aged 13–17 at a state school in Bucaramanga, Colombia were randomized to an intervention group which participated in 2, one hour combined resistance and aerobic training sessions per week (RT-AT) or to a control group which continued to attend their twice weekly, 1-hour physical education class (PE). RT-AT stopped attending PE, and their in-school training sessions were supervised by a qualified graduate and undergraduate students. Prior to and at the end of the 22-week study anthropometric and body composition measures were taken; BMI, fat and lean mass (bioelectrical impedance analysis (BIA)), sum of skinfolds (∑-skinfolds), and physical fitness assessed; upper body strength (handgrip strength (HGS)), lower body strength (standing long jump (SLJ)), estimated Vo2 max (20 m shuttle run) and flexibility. Student t–tests were used to assess potential changes between baseline and end of study on an intention-to-treat basis (analysis includes all intervention subjects regardless of attendance levels). Results: In both groups BMI significantly increased and there was no significant change in estimated Vo2max, flexibility or lean mass. In PE, fat mass significantly increased, there was a significant decrease in SLJ and a non-significant decline in HGS. In RT-AT, ∑-skinfolds significantly decreased and HGS significantly increased. Conclusion: Over 22 weeks, adolescent girls participating in curriculum PE classes gained total fat mass and showed no change in subcutaneous fat. In contrast, RT-AT led to no change in total fat mass, and significant declines in subcutaneous fat. Of concern, there was no improvement in HGS and a decline in SLJ in PE. RT-AT eliminated the decline in SLJ and promoted a significant increase in HGS. Improvement of aerobic fitness appear to require a greater stimulus than provided by either PE or by the RT-AT intervention we implemented. Practical Applications: In a middle income country, a structured exercise training program which includes resistance training can successfully be delivered within the school curriculum. Standard PE class appears to be an inadequate stimulus for strength in adolescent females, while a time-matched RT-AT program enhanced aspects of strength and body composition associated with cardiometabolic health.

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Table 1.:
Anthropometric, body composition and physical fitness in 12–17 year old girls, pre and post 22 weeks of either combined aeróbic + strength training (intervention) or physical education class (control).

Thursday, July 11, 2019, 2:00 pm–3:30 pm.

Acute Effects of Moderate Aerobic Exercise Versus High Intensity Interval Training on Oxygen Uptake, Heart Rate, and Perceived Exertion

M. Kelly, C. Godoy, R. Machado, and P. Costa

California State University, Fullerton

The appeal of high intensity interval training (HIIT) is time efficiency. However, the effects of HIIT compared to moderate aerobic training during and after the exercise are still unclear. Purpose: To compare the effects of an acute bout of moderate aerobic versus HIIT exercise on relative Vo2, heart rate (HR), and rating of perceived exertion (RPE). Methods: Seventeen men (mean ± SD = 22.2 ± 1.6 years, 80.0 ± 9.7 kg, 176.8 ± 6.5 cm) and 15 women (22.4 ± 2.2 years, 62.8 ± 10.5 kg, 164.1 ± 4.9 cm) volunteered for this study. Resting HR, baseline Vo2, Vo2max, and maximal resistance on a cycle ergometer (Watts) were measured in a familiarization session. In the following 2 visits, subjects took part in randomly-ordered HIIT or moderate exercise conditions. Vo2 was collected for 5 minutes before exercise to establish a baseline, and after exercise in 5-minute intervals for 30 minutes. In the HIIT protocol, participants exercised for a total of 15 minutes, consisting of 5 repetitions of exercise at 90% of peak power for 1 minute, alternated with 2 minutes of active recovery at 50% of peak power. The moderate exercise consisted of 30 minutes of exercise at 40–59% of heart rate reserve. HR was collected for every minute, and RPE was collected every 5 minutes for moderate and every minute for HIIT. Results: There was a significant main effect for time (p < 0.001), condition (p = 0.019), and sex (p < 0.001) for Vo2. Oxygen uptake was higher immediately post-exercise and remained 6–10% higher until 10 minutes compared with baseline (p < 0.05) (Figure 1). The moderate condition had a higher Vo2 than the HIIT (p < 0.05) and men had a higher oxygen uptake than women (p < 0.001). There was a main effect for HR for condition (p < 0.001). Mean HR was higher for HIIT (143.9 ± 13.3) than the moderate (135.4 ± 9.6) condition. There were no differences for RPE between conditions or sex (p > 0.05). Conclusion: Both moderate and HIIT exercise caused an increased relative Vo2 until 10 minutes after exercise was completed and a there was a higher increase in HR during HIIT. Practical Applications: Moderate intensity exercise and longer HIIT protocols might be beneficial for individuals seeking exercise for weight loss or weight management due to the increased energy expenditure. Individuals pursuing time efficient exercise protocols may consider HIIT for comparable benefits to their moderate intensity albeit longer protocols.

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Figure 1.:
Oxygen Uptake for Moderate Exercise and High Intensity Interval Training. Means (±SE) for oxygen consumption before and after moderate aerobic exercise and high intensity interval training. *Significant difference from baseline (p ≤ 0.05).

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Comparison of the Army Physical Fitness Test and the Occupational Physical Assessment Test in Reserve Officer Training Corps Cadets for Assessing Physical Combat Readiness

C. Draicchio, M. Fyock-Martin, and J. Martin

George Mason University

United States Army Soldiers are expected to maintain a high level of physical fitness at all times to ensure capability of performing job related duties. Common soldier tasks include single (maximal) lifting and lowering, repeated lifting and lowering, lifting and carrying, casualty drag/carry, push and pull tasks, digging, crawling, load bearing marching/walking/running for various distances, climbing/jumping over obstacles, moving quickly with agility, and a combination of these (multi-activity tasks). The Army Physical Fitness Test (APFT) is used to asses an individual soldier and unit's readiness to deploy. The APFT has been shown to assess upper body and lower body muscular endurance and aerobic capacity but fails to assess occupational demands of Army Soldiers. The Occupational Physical Assessment Test (OPAT) is a test used only when a soldier first enters the Army to determine whether they can meet the demands of a combat or non-combat related job. Purpose: To investigate the relationship between the Army Physical Fitness Test (APFT) and the Occupational Physical Assessment Test (OPAT). Methods: A retrospective analysis of data from 93 Cadets (76 men and 17 women, age 18–28) of the Army Reserves Officer Training Corps program at George Mason University in Fairfax, VA was conducted. The Cadets completed the APFT and OPAT protocols per Army standards. The APFT consists of 2 minutes of maximum push-up repetitions, 2 minutes of maximum sit-up repetitions, and a 2-mile timed run. The OPAT consists of a standing long jump, seated power throw, a deadlift test, and interval aerobic run. Pearson's correlation coefficients were computed to examine the strength of relationships between individual test events. The magnitudes of the correlation coefficients were interpreted using Cohen's scale: <0.10, trivial; 0.10–0.29, small; 0.30–0.49, moderate; >0.50, large. Results: The results of the correlational analysis is displayed in the table below. All of the correlations were statistically significant. Large positive correlations were found between the following tests: seated power throw & deadlift, seated power throw & pushup, deadlift & pushup and push-up & sit-ups. Large negative correlations were found between the following tests: interval aerobic run & 2-mile run, push-ups & 2-mile run, Large correlations were found amongst all 3 tests on the APFT. The 4 tests on the OPAT had 1 large, 3 moderate and 1 small correlation. Conclusion: The OPAT appears to be a more robust fitness assessment than the APFT. Thus, performance on the APFT may not be a valid indicator of a soldier's readiness for combat. Practical Applications: The results of this study indicate that fitness tests currently used by the Army may favor different fitness components. Tactical strength and conditioning facilitators should understand differences in fitness tests utilized by tactical organizations and design training programs accordingly.

Intercorrelation matrix for APFT and OPAT tests.

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Table 1.:
Intercorrelation matrix for APFT and OPAT tests.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Don't Drag Me Down: Investigating the Body or Victim Drag in Graduated and Incoming Deputy Sheriff Recruits

R. Lockie, M. Moreno, K. Cesario, K. Balfany, J. Dulla, R. Orr, and J. Dawes

California State University, Fullerton

Introduction: An essential job task for law enforcement officers is a body drag (BD), where they must drag a civilian or officer from a hazardous environment. In California, a BD with a 75-kg dummy is a test within the Work Sample Test Battery (WSTB). Recruits must drag the dummy 9.75 m in under 28 seconds to attain points for the WSTB. Maximal strength should contribute to this task, although this quality is not often a focus of traditional law enforcement academy training. This is notable considering current US population data; the average adult male weighs ∼89 kg, while the average adult female weighs ∼77 kg. This suggests the dummy mass should increase to match the mass of people an officer may encounter, especially if the officer may need to drag a fellow officer who is wearing their daily duty loads. However, further investigations of the BD are required before adjustments to the dummy mass are made. Purpose: To compare the BD between graduated (GRAD) and incoming (INC) male and female Deputy Sheriff recruits, determine percentile rankings for the BD in GRAD recruits, and detail how INC recruits compare to this standard. Methods: Retrospective analysis on 9 GRAD classes (males = 542; females = 101), and 2 INC (males = 145; females = 46) from one agency was conducted. The GRAD classes completed the BD in the final weeks of their 22-week academy; the INC completed the BD in the week prior to their academy. The BD required the recruit to lift the dummy to standing and drag it 9.75 m as quickly as possible. Timing commenced once the dummy began to move during the drag from the standing position. To compare differences between the GRAD and INC recruits by sex, a one-way ANOVA with Bonferroni post hoc was utilized. GRAD and INC recruits were ranked according to BD, and allocated into percentile ranks, based on GRAD data, with the number of males and females in each rank indicated. Results: The GRAD males (4.76 ± 0.84 seconds) completed the BD faster than all groups. The INC males (6.23 ± 2.23 seconds) were faster than the 2 female groups, and the GRAD females (6.95 ± 1.89 seconds) were faster than the INC females (10.60 ± 3.49 seconds; p < 0.01 for all comparisons). The percentile ranking data is shown in Table 1. There was a disproportionate number of females in the lower percentiles for both the GRAD (69% of females in the bottom 20%) and INC (98% of females in the bottom 20%) groups. Conclusion: GRAD recruits generally completed the BD faster than INC recruits, which was expected as they have had specific training. Nonetheless, most INC recruits completed the BD within acceptable WSTB standards. What is notable, however, is the performance of females in the BD. Although males tend to be stronger and heavier, appropriate absolute strength training can still improve this quality in females, which could be life-saving if they need to complete the BD when on shift. Practical Applications: LEA staff should place a greater emphasis on developing absolute strength in their recruits, especially in female recruits, who on average, have lower strength values than their male counterparts. If there are changes made to the dummy mass due to population increases in body mass, absolute strength training should be a greater focus of academy. INC recruits should be encouraged to develop their absolute strength prior to academy, as this would be an important quality for tasks such as the BD.

table13
Table 1.:
Percentile rankings for body drag (BD) time based on graduated (GRAD) recruit data, and comparisons with incoming (INC) recruits.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Affective Responses to On-Site Resistance Exercise in Young and Older Career Firefighters

G. Gerstner, A. Trivisonno, M. Laffan, J. Mota, H. Giuliani, and E. Ryan

University of North Carolina at Chapel Hill

Firefighters often have substandard fitness levels regardless of the physical demands of their job. Resistance training (RT) can be an effective strategy to improve occupational performance and reduce on-duty injures. However it is unclear if the affective response to RT differs between young and older firefighters, which may predict long-term adherence. Purpose: The purpose of this study was to examine the influence of age on affective responses (attitude, mood, self-efficacy, intentions, enjoyment, preference) toward an acute bout of RT at the fire station. Methods: Forty-two male firefighters [21 young: 25.71 ± 3.41 years (18–30), stature: 181.09 ± 6.25 cm, mass: 92.98 ± 17.90 kg; 21 older: 50.57 ± 3.79 years (45–60), stature: 176.49 ± 6.65 cm, mass: 99.06 ± 30.84 kg] volunteered for this investigation. Testing occurred on 2 separate occasions at local fire stations. During the first session, participants were familiarized with 4 RT exercises (deadlift, shoulder press, lunge, upright row) using commercially available dumbbells. A multi-repetition maximum (RM) assessment was performed to estimate 1RM for each exercise. The second testing session (n = 38) consisted of an acute RT bout of the 4 exercises starting with a brief warm-up set (40% 1RM) followed by 3 sets of 8–10 repetitions (80% 1RM) in a circuit style. Participants then completed a post-exercise questionnaire examining the following constructs regarding the RT bout: attitude, mood, self-efficacy, intentions, enjoyment, and preference. Internal consistency of the constructs with multiple questions (self-efficacy, intentions, enjoyment) were measured using Cronbach's alpha. Mann–Whitney U tests were used to determine differences in each construct between the young and older firefighters. An alpha level was set a priori at 0.05 for all analyses. Results: The Cronbach's alpha for self-efficacy, intention, and enjoyment exceeded the criterion of 0.70 suggesting high internal consistency (0.85–0.93). There were no differences between the age groups for attitude, mood, self-efficacy, intentions, enjoyment, and preference (Table 1; p = 0.080–0.803). Conclusion: These findings suggest that young and older firefighters have similar attitude, mood, self-efficacy, intentions, enjoyment, and preference towards the bout of RT. Furthermore, 86% of the firefighters agreed or strongly agreed the workout could be easily implemented in their department and 81.6% felt ≥80% confident engaging in this form of exercise at least 2 times per week over the next 3 months. Additionally, 89% reported feeling good to very good about the RT bout, and 84.2% reported somewhat to extreme fondness for the workout. Practical Applications: The results suggest that a brief RT routine is potentially a feasible and cost-effective (limited equipment) strategy that scored favorably on affective responses in both young and older firefighters.

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Thursday, July 11, 2019, 2:00 pm–3:30 pm

Relationship Between Previous Sport History and Lower Extremity Power in U.S. Army Soldiers

B. Hotaling, K. Taylor, P. Frykman, B. Spiering, P. Bartlett, J. Hughes, and S. Foulis

USARIEM

Introduction: Muscular power has been linked to success in a variety of anaerobic sports. Similarly, this fitness component has been shown to correlate with a service member's performance in their daily military tasks. Unfortunately, training for anaerobic power is not a focal point during Army Basic Combat Training (BCT) and the aerobic system has only a slight involvement with anaerobic activities. The role of prior history of participation in anaerobic sports play in determining lower extremity power, as measured by the standing VJ test, has yet to be evaluated in U.S. Army recruits. Purpose: To determine the relationship between metabolic demands, as determined by competitive sport history prior to BCT, and performance on vertical jump testing. Methods: The vertical jump of 911 (265 women and 646 men) trainees was measured prior to starting basic training. Body mass and VJ height were used to calculate VJ peak power using the Harman equation. Subjects were surveyed for previous history of playing sports. Subsequently, based on the NSCA's Essentials of Strength Training and Conditioning, metabolic demand for sports played was classified into 4 categories (no sport history, low, moderate, high) for 2 anaerobic systems (phosphagen, glycolytic) and for the aerobic system. A linear model mutually adjusted for each of the 3 systems tested (phosphagen, glycolytic, and aerobic) and sex was used to estimate the effect of each system's metabolic demand on peak power. For example, a previous sport history of volleyball was classified as high-phosphagen and moderate-glycolytic. Results: There was a significant relationship between an increase in categories for both the phosphagen (effect = 41.96, p-value < 0.001) and aerobic systems (effect = 42.81, p-value < 0.001) and peak power. This relationship was not detected for the glycolytic (effect = 1.11 p-value = 0.96) system. For every increase in the number of sports played in the high category for the phosphagen system, there was a 49.63 watts increase in peak power (p-value < 0.001). Conclusion: This study found a comparable relationship between muscular power production and a prior history of participation in sports as classified by their metabolic demands in the phosphagen and aerobic systems. Participation in a higher number of sports classified as placing a high demand on the phosphagen system showed an increase in peak power performance. Practical Applications: U.S. Army BCT has primarily focused on aerobic activities such as running, but these findings suggest that the sports that place high demands on either the phosphagen system or the aerobic system produced similar results in peak power measurements. These results may indicate that training for anaerobic power may be just as valuable as aerobic training when it comes to lower extremity power training and important to consider when setting up training protocols that will properly prepare a service member to meet the demands of their diverse military tasks. Fitness professionals should be aware of an individual's previous sport history and current occupational demands before individualizing training routines. Disclaimer: The views expressed in this abstract are those of the authors and do not reflect the official policy of the Department of Army, Department of Defense, or the U.S. Government.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Association Between Isometric Leg-Back Strength and Lower Body Power in Law Enforcement Officers

J. Bone,1 B. Stone,2 E. Hernandez,3 R. Lockie,3 R. Orr,4 C. Kornhauser, R. Holmes, and J. Dawes

1University of Colorado- Colorado Springs; 2University of Oklahoma/United States Olympic Committee; 3California State University, Fullerton; and 4CSU Fullerton

Law enforcement personnel must possess a high level of physical capabilities that often include dynamic movements which are outcomes of both lower body strength and power. These qualities are often expressed in athletic environments where significant relationships have been observed between dynamic lower-body strength and power. Thus, it’s speculated that similar relationships may exist between these measures in law enforcement personnel. Purpose: To determine if significant relationships exist between lower body strength and power in law enforcement personnel. Methods: Archival data from a US law enforcement agency (n = 595, age: 39.2 ± 8.1 years, Ht: 179.9 ± 7.4 cm, Body mass: 92.54 ± 16.2 kg) were used in the present study. Lower body strength (leg and back) were assessed via a lower body dynamometer in both absolute; (LBDa) and relative (LBDr) body mass. Vertical jump height (VJ) and body mass (kg) were used to determine estimated power output (PAPw) via Sayer's equation (Sayers et al. 1991). Pearson product moment correlation (p < 0.05) was performed to determine the relationship between LDBa, LBDr, VJ and PAPw. Results: Significant relationships were observed between LBDa and VJ (r = 0.403, p = 0.0001), LBDa and PAPw (r = 0.605, p = 0.0001) and LBDr and VJ (r = 0.564, p = 0.0001) whereas no relationship was observed between LBDr and PAPw (r = −0.049, p = 0.232). Conclusion: The present study demonstrates that absolute lower body strength and power are significantly related, both in terms of vertical jump and estimated power output while relative lower body strength was related to vertical jump but not estimated power output. These suggest that law enforcement personnel require similar strength and power relationships as seen within athletic populations. Practical Applications: The present findings indicate consideration when planning strength and conditioning programs for law enforcement personnel. Specifically, the myriad of dynamic movements that are required by these personnel indicate the need for lower body strength and power development. However, outcomes between these may be different such that absolute strength may be more closely linked with absolute power production whereas relative strength may exhibit greater enhancement of vertical jump capabilities.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Objective and Subjective Responses to Submaximal and Maximal Aerobic Capacity Assessments in Firefighters

E. Smith,1 R. Flees,1 D. Cornell,2 V. Kleiss,1 and K. Ebersole

1University of Wisconsin-Milwaukee; and 2University of Massachusetts Lowell

Sudden cardiac death accounted for 48% of all firefighter (FF) deaths in 2017. Following activity, the risk of cardiac mortality may be increased when parasympathetic nervous system (PNS) reactivation is delayed. Higher intensity activity and the accumulation of metabolic biomarkers, such as blood lactate (La), are suggested to be inversely related to post-exercise PNS reactivation. Objective measures of PNS reactivation, such as heart rate recovery (HRR) and heart rate variability (HRV), are not always viable options for fire departments. Rating of perceived exertion (RPE) is a cost-free subjective alternative to HR monitoring, yet, the application of RPE within FFs remains unknown. Given that firefighting includes both submaximal and maximal intensity tasks, it is important to determine if objective (La, HRR, & HRV) and subjective (RPE) measures respond similarly during recovery from tasks of different intensities. Purpose: Examine the objective and subjective responses following submaximal (Queen's College Step Test [ST]) and maximal (Treadmill Test [TT]) assessments of aerobic capacity in FFs. Methods: La, HRR, HRV, and RPE were collected prior to (PRE), immediately post (0′), and 10-minutes post (10′) ST and TT assessments in 32 male FFs (age: 39.44 ± 9.36 years; height: 178.93 ± 5.56 cm; body mass: 88.08 ± 11.55 kg). Each measure was normalized to its respective PRE value (%PRE) for all analyses. The effect of Test and Time for each measure was assessed via a 2 × 3 repeated-measures analyses of variance (RMANOVA). Bonferroni adjusted one-way RMANOVAs and paired t-tests were used to further delineate the effects of Time within each Test and Test at each Time point. An alpha of 0.05, 0.017, and 0.025 were used for the 2 × 3 RMANOVAs, one-way RMANOVAs, and paired t-tests, respectively. The effect size for each paired t-test was calculated using Cohen's d. Results: Significant Test × Time (p < 0.001) interactions and main effects for Test (p < 0.001) and Time (p < 0.001) were identified for each measure (La, HRR, HRV, RPE). The results from post-hoc pairwise and simple effect analyses are presented in Table 1. Conclusion: Although each measure confirmed that TT was more intense than ST at 0′ and 10′, regardless of test, only RPE returned to a level near PRE after 10′. These findings suggest that while FFs are able to discern tasks of different intensities, FFs may perceive recovery to be complete, despite elevated La and suppressed PNS activity. Practical Applications: Given the high prevalence of sudden cardiac deaths among FFs and the relationship between suppressed PNS reactivation and cardiac mortality, fire departments should use caution when relying solely on self-perceived recovery, as such information may not fully indicate the recovery status of a FF. Future research should determine if the utilization of RPE within FFs can be improved following an RPE familiarization protocol and examine the response of these objective and subjective measures following fire training and/or live fire service calls.

table14
Table 1.:
La, HRR, HRV, and RPE responses following the ST and TT (mean ± SD).

Thursday, July 11, 2019, 2:00 pm–3:30 pm.

Relationship Between Gastrocnemius Muscle Length and Single-Leg Dynamic Balance Ability Among Male Career Active-Duty Firefighters

D. Cornell, M. Oo, and K. Ebersole

University of Massachusetts Lowell

U.S. firefighters experienced more than 58,000 injuries in 2017 and 20% of these injuries were a result of falls, slips, and trips. Previous research suggests that poor single-leg dynamic balance ability, as assessed by the Y-Balance Test (YBT), can predict future musculoskeletal injury among various athlete populations. Previous research also has demonstrated that limited ankle dorsiflexion range of motion (DFROM) negatively influences single-leg dynamic balance ability, and in particular, the anterior reach direction of the YBT. Since a lack of gastrocnemius muscle length can limit DFROM, and previous research also suggests that a lack of gastrocnemius muscle length can influence lower extremity movement mechanics among firefighters, it is possible that gastrocnemius muscle length may influence single-leg dynamic balance among firefighters as well. Purpose: To examine the relationship between gastrocnemius muscle length and single-leg dynamic balance ability among active-duty career firefighters. Methods: Forty-nine male career active-duty firefighters volunteered to participate (mean ± SD, age: 40.7 ± 7.9 years; height: 179.2 ± 5.5 cm; body mass: 90.8 ± 9.1 kg). Gastrocnemius muscle length was assessed by passively measuring bilateral ankle DFROM (°) using a goniometer with participants in supine and knees fully extended. Left and right anterior (YBTANT), posterolateral (YBTPL), and posteromedial (YBTPM) YBT reach distances were normalized to respective limb lengths (%). Left and right composite YBT (YBTCOMP) scores were formed by summing YBTANT, YBTPL, and YBTPM, and dividing by 3. Bivariate correlations were utilized to examine the relationships between bilateral DFROM and bilateral YBTANT, YBTPL, and YBTPM reach distances, as well as YBTCOMP scores. Results: Bivariate correlations identified a statistically significant direct relationship between left DFROM and left YBTANT reach distance (r = 0.279, p = 0.026), and a direct relationship that was approaching statistical significance between right DFROM and right YBTANT reach distance (r = 0.205, p = 0.079). However, no statistically significant relationships (p > 0.05) were identified between bilateral DFROM and bilateral YBTPL reach distance, YBTPM reach distance, and YBTCOMP scores (Table 1). Conclusion: Results of this study suggest that restricted gastrocnemius muscle length is associated with poor performance during the anterior reach direction of the YBT among male career active-duty firefighters. However, this restriction in gastrocnemius muscle length may not be associated with overall single-leg dynamic balance ability. Practical Applications: In an effort to improve performance during the anterior reach direction of the YBT, and to reduce musculoskeletal injury risk among firefighters, practitioners should proactively incorporate interventions designed to increase gastrocnemius flexibility.

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Thursday, July 11, 2019, 2:00 pm–3:30 pm

Influence of Alarm Type on Heart Rate Response in Firefighters

R. Marciniak,1 D. Cornell,2 E. Smith,1 K. Ebersole, and C. Tesch3

1University of Wisconsin-Milwaukee; 2University of Massachusetts Lowell; and 3City of Milwaukee Fire Department

Introduction: Sudden cardiac death is the leading cause of on-duty death of firefighters (FF) in the U.S., accounting for 48% of duty-related fatalities in 2017. It has been suggested that an increase in the activity of the sympathetic nervous system (SNS) following the sound of an alarm tone may prompt a change in heart rate (HR), potentially increasing risk for cardiovascular stress. Previous research has suggested that in response to an alarm tone, HR can increase up to 47 beats per minute. However, this response may vary depending on tone type. The potential difference in HR response between a medical (MED) call tone (i.e., double, short tone) and a fire (FIRE) call tone (i.e., a single, long tone) remains unclear. Purpose: To examine the influence of alarm tone type (MED, FIRE) on HR responses in active-duty FFs. Methods: HR was continuously collected during 24-hour shifts using a remote physiological system in 16 male active-duty career FFs (37.94 ± 5.96 years, 180.51 ± 5.72 cm, 97.01 ± 9.93 kg) from a Midwest metropolitan fire department. Using official department time-stamped call logs, the HR data was downloaded and marked for the time the alarm tone sounded (HRTONE) and the peak HR response (HRPEAK) following the tone yet prior to the crew departing the station. HR data used for analysis represented any call that occurred during a shift where complete HR data was available (i.e., no loss in signal was observed). All HR data was converted to a percentage of the participants estimated maximal HR (HRMAX = 220—age). A 2 (call type) × 2 (HR response) split-plot mixed-model repeated measures analysis of variance with follow-up main and simple effects was used to identify statistically significant (p < 0.05) differences between HRTONE and HRPEAK following MED and FIRE call tones. Results: A significant call type × HR response interaction effect (F1, 79.894 = 14.700, p < 0.001) was identified, with significant main effects for both call type (F1, 23.061 = 7.679, p = 0.011) and HR response (F1, 33.793 = 68.842, p < 0.001). Follow-up tests indicated that HRPEAK was significantly (p < 0.001) greater than HRTONE for both MED (56.6 ± 2.7% vs 42.4 ± 2.1%) and FIRE (65.9 ± 2.7% vs 44.4 ± 2.0%) calls. While no significant (p = 0.955) differences in HRTONE were found between call type, HRPEAK was significantly (p < 0.001) greater during FIRE calls than MED calls. Conclusion: The present data suggests that a fire call tone elicits a greater heart rate response than medical call tones. Given the link between heart rate modulation and sympathetic nervous system activity, results from the present study suggest that a fire call tone may place a greater overall load on the cardiovascular system. Practical Applications: FFs are subjected to multiple call tones during each shift. It is possible that FFs working at a location with a high call volume, specifically fire calls, may experience higher sympathetic demands of the heart. Increases in sympathetic nervous system activity are likely necessary to allow FFs to meet the physical demands of a fire call, however, it is possible that chronic exposure to fire tones may increase the cardiovascular risk profile of a FF. With cardiovascular disease being the largest contributor to FF mortality, and sudden cardiac death being the leading cause of on-duty death, future research should examine interventions targeting autonomic nervous system regulation as a means to attenuate the response to a fire tone.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Bilateral Limb Support During Handgun Aiming and Shooting Is More Accurate Than Unilateral Limb Support

K. Kelleran,1 S. Morrison,2 D. Swain,2 and D. Russell2

1Bridgewater College; and 2Old Dominion University

Purpose: Factors affecting handgun shooting accuracy include both intrinsic and extrinsic liabilities. Oscillations of the limb known as postural tremor are included as one of these factors and may be have both intrinsic and extrinsic influences. Inherent stability can be added by the addition of a second limb to support the handgun during aiming and shooting. The current study examines accuracy and tremor during unilateral and bilateral support. Methods: Twenty experienced handgun shooters (12 male, 8 female, age 28.1 + 3.9 years) used a training handgun to aim and shoot at a bullseye target 6.4 meters away. The handgun system was equipped with a laser shot recorder for accuracy measures. Unilateral and bilateral limb support conditions were assessed during both shooting and aiming tasks. Participants, in a counter balanced order, aimed or took 5 shots at the target during each 10 seconds trial, 5 trials per condition. Accelerometers were affixed to the upper arm (UA), forearm (FA), hand (HA), and gun barrel (GB). Amplitude (RMS) and regularity (ApEn) of the acceleration signals were computed. Results: Compared to single limb support, bilateral limb support was significantly more accurate (Shot score: Uni- 2.68 + 1.34, Bi- 2.17 + 1.12, F1,19 = 129.05, p < 0.001). During the aiming conditions bilateral limb support decreased the amplitude (VT: F1,19 = 281.30, p < 0.001, ML: F1,19 = 389.77, p < 0.001) and increased the irregularity (VT: F1,19 = 314.8, p < 0.001, ML: F1,19 = 314.45, p < 0.001) of the acceleration signal when compared to unilateral limb support conditions. Conclusion: Bilateral limb support reduced the magnitude of tremor and increased the irregularity of these accelerations, which may have contributed to improved shooting accuracy. This may be due to the second limbs influence upon neurological and mechanical factors of the segments, assistance to resistance to gravity, or the effort of control. Practical Applications: Overall the results suggest limb support, and likely support in general, plays a large role in both accuracy and accelerations of handgun shooting.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Effects of Caffeine Supplementation on Maximal Strength Is Not Influenced BYCYP1A2 Genotype

S. Fleming,1 R. Colquhoun,2 P. Tomko,1 M. Magrini,3 N. Banks,1 M. Ferrell,1 and N. Jenkins1

1Oklahoma State University; 2University of South Alabama; and 3Creighton University

Introduction: Caffeine is the most widely consumed stimulant in the world and is often used by athletes to improve exercise performance. Despite this, the effects of caffeine on performance have been shown to be highly variable and subject-specific. The cytochrome P450 1A2 enzyme (CYP1A2) is responsible for up to 95% of caffeine metabolism, and a single nucleotide polymorphism (SNP) in the CYP1A2 gene has been suggested to influence the ergogenic effects of caffeine. Purpose: The purpose of this study was to examine the influence of the CYP1A2 genotype on the effects of caffeine on maximal strength in college-aged males. We hypothesized that differences in CYP1A2 genotype would explain variability in the effect of caffeine on maximal strength. Methods: Thirty-eight college-aged males (age = 23 ± 3; height = 177 ± 5 cm; weight = 88 ± 13 kg) completed 2 experimental sessions in which isometric maximal voluntary torque (MVT) of the knee extensors was measured prior-to and 1-hour after consuming caffeine (CAF; 6 mg/kg bodyweight) or placebo (PLA; all-purpose flour). Each visit was separated by 7 ± 1 day and took place at the same time of day (±1 hour). A saliva sample was collected from each subject in order to determine genotype for CYP1A2 as AA (n = 23) AC/CC (n = 15). A 2 (CAF vs. PLA) × 2 (Pre vs. Post) × 2 (AA vs. AC/CC) mixed factorial ANOVA was run to examine potential differences in MVT. Post hoc dependent samples t-tests and one-way ANOVAs were run when necessary. Results: There was a significant condition × time interaction (F1,37 = 7.563; p = 0.009). Follow-up analyses indicated that there was a significant decrease in MVT from pre-to post-supplementation in the PLA condition (p = < 0.001), but not in the CAF condition (p = 0.094). No other interactions or main effects were observed (all p > 0.05). Conclusion: Our results show a maintenance of MVT following acute caffeine consumption following an hour of rest, but a significant decrease in MVT in the PLA condition. Interestingly, we found that the CYP1A2 genotype did not play a role in the effect of caffeine on MVT. Practical Applications: Caffeine supplementation did not increase MVT, but it did maintain MVT following an hour of passive rest, whereas MVT decreased in the placebo condition. Further, CYP1A2 genotype does not appear to influence the ergogenic effect of caffeine on maximal strength.

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Thursday, July 11, 2019, 2:00 pm–3:30 pm

The Influence of Multiple Practices on Energy Availability in Football

A. Jagim,1 G. Wright,2 J. Kisiolek,3 J. Luedke,2 J. Erickson,1 and C. Kerksick

1Mayo Clinic Health System; 2University of Wisconsin—La Crosse; and 3University of Northern Colorado

Energy availability is a metric used to assess the energy status of an athlete during training and is defined as the remaining available energy for basic physiological function after activity energy expenditure has been quantified. Values <30 kcal/kg FFM are often classified as low energy availability (LEA) and can negatively influence health and performance. It is currently unknown how multiple practices in a day may impact energy availability in football players. PURPOSE The purpose of this study was to assess differences in energy availability between single and multiple practice days during pre-season training in Division III American football players. Methods: Seventeen (Linemen; n = 6; Non-linemen; n = 11) Division III football players (Ht: 1.80 ± 0.6 m; BM: 99.1 ± 60.1 kg; FFM: 79.7 ± 8.6 kg; BF%: 19.3 ± 8.6%) completed a body composition assessment using air displacement plethysmography (BodPod, Cosmed, USA) to determine fat-free mass (FFM) before the start of pre-season training. Training camp consisted of 14 days of practices (1-Practice Days; n = 10; 2-Practice Days; n = 4). For each day of practice, players recorded their dietary intake using a commercially available nutrition program (MyFitnessPal, Under Armor, USA). Players were also equipped with a physiological monitoring device and accelerometer (Bioharness 3, Zephyr Technology Corp., Annapolis, MD) to determine activity energy expenditure (AEE) for all practices. Energy availability (EA) was then calculated by subtracting the AEE from total daily energy intake, and expressed over FFM. Data from all single (1P) and two-practice (2P) days were collapsed and expressed as a single average per day. Paired sample t-tests were used to assess differences in EA between practice day type and analysis of variance was used to compare differences in EA between position groups for 1P and 2P days. Results: Estimated energy availability values were significantly lower on 2P days compared to 1P for all players (2P: 20.2 ± 8.2 vs. 1P: 30.9 ± 10.9 kcal/kg FFM; p < 0.001). There were no differences in EA between position groups during 1P (p = 0.94) or 2P (p = 0.95) days. Linemen yielded significantly higher AEE values on 1P (Linemen: 1,614 ± 124 vs. Non-linemen 1,396 ± 171 kcal; p = 0.015) and 2P (Linemen: 2,469 ± 255 vs. Non-linemen: 2,192 ± 249 kcal; p = 0.046) days compared to non-linemen. Conclusion: Division III football players appear to be at risk of LEA and multiple practices in a day may further increase this risk as values dropped to near 20 kcal/kg FFM, which is well below the threshold of 25 kcal/kg FFM that is often used in males to classify those at high risk for physiological dysfunction. Practical Applications: Periods of intense training may predispose athletes to LEA, which can have negative implications for body mass, hormonal function, immune function, bone health, and performance. Because of the high AEE values during pre-season training, particularly in linemen, football players should focus on consuming adequate energy to offset the high energy expenditure and ensure adequate available energy.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Estimated Energy Expenditure During NCAA Division I College Football Practice

E. Sobolewski1 and M. Lochbaum2

1Furman University; and 2Texas Tech University

Measuring physiological demands of sport is becoming increasingly easier to do with the onset of wearable technology, yet very little research has been done with NCAA college football players. Traditionally heart rate (HR) has been used to estimate caloric expenditure of exercise and has shown to be a valid measure, yet with the integration of HR monitors to measure fatigue and load of practice, HR data has not been used to estimated caloric expenditure of football practice. In fact, there is little to no evidence of the metabolic demand of practice. Purpose: The purpose of this study was to estimate caloric expenditure during football practice across position group. Methods: Thirty players (age, 20.0 ± 1.0 years; mass 101.8 kg: height 183.4 ± 9.2 cm) wore heart rate monitors for 10-weeks during the fall football season. They were divided into position groups and compared. The position groups included 2 quarterbacks (QB: 191.2 ± 3.3 cm, 99.3 ± 3.3 kg), 3 running backs (RB: 173.3 ± 2.8 cm, 85.9 ± 2.8 kg), 6 wide receivers (WR: 180.4 ± 9.3 cm, 85.3 ± 8.5 kg), 5 offensive linemen (OL: 194.7 ± 3.5 cm, 135.6 ± 7.8 kg), 5 defensive linemen (DL: 190.8 ± 3.4 cm, 120.4 ± 18.7 kg), 5 linebackers (LB: 184.4 ± 2.0 cm, 99.2 ± 1.5 kg), and 4 defensive backs (DB: 182.0 ± 7.3 cm, 80.0 ± 6.6 kg). Energy Expenditure (EE) was estimated using HR data. Results: Estimated EE (kcals) for each position group. QB: 1,625.3 ± 530.8, RB: 1,530.7 ± 418.5, WR: 1,595.6 ± 397.3, OL: 1,677.4 ± 498.2, DB: 1,638.1 ± 477.5, LB: 1,407.3 ± 441.1, DL: 1,575.8 ± 493.3. There was no significant (P > 0.05) difference in EE between position groups. Conclusion: When evaluating energy expenditure, it appears that caloric expenditure is similar across all position groups. This may indicate that metabolic demands are similar across position groups as fitness level, body type, and nature of the position seem to equate internally as measured by HR. DBs may be lighter, smaller, and in better aerobic shape than their DL counter parts who are larger, taller, and more adapted to short powerful bursts, rather than high speeds and long distances. All of this equates to practice having the same metabolic cost across position groups. This is the first research of its kind to evaluate EE in college football players, but it can be used as a guide to how many calories are burned during practice. Practical Applications: The estimated caloric expenditure of practice is around 1,500 kcals and should be accounted for in a nutritional plan for weight management and recovery throughout the season. This is valuable information for performance staffs.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

The Effects of Beta Alanine and Sodium Bicarbonate Supplementation on Anaerobic Performance in Trained Males

C. Swart1 and J. Peacock2

1Bridgewater State University; and 2Merrimack College

The study was designed to examine the effects of chronic beta-alanine supplementation and acute sodium bicarbonate supplementation on anaerobic performance. Ten trained males (O2peak 52.14 ± 4.24 ml−1·kg−1·min) performed an 8 minutes anaerobic exercise cycling protocol before, after chronic beta-alanine supplementation, and after the combination of chronic beta—alanine and acute sodium bicarbonate supplementation. An 8 minutes intermittent cycling protocol was used for each session with 30 seconds of maximum effort followed by 30 seconds of active recovery for 8 rounds. The performance variables measured every min included lactate, RTW (relative total work), RAAP (relative average anaerobic power), TREPS (total repetitions), RPE, O2 and RER.  Significant interactions were found for RTW, RAAP, TREPS and RPE.  Although RTW and RAAP were only significant at one time point (3:30) a trend toward an increase in RTW and RAAP was found. A trend toward higher RTW and RAAP during the 8 minutes intermittent cycling protocol may indicate the benefit of chronic beta-alanine combined with acute sodium bicarbonate supplementation outside the widely studied exercise length of 60–240 s.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Fish Oil Supplementation Attenuates Muscle Stiffness after Eccentric Contractions of Human Elbow Flexors

E. Ochi,1 K. Yanagimoto,2 H. Ueda,3 and Y. Tsuchiya

1Hosei University; 2Nippon Suizan Ltd.; and 3Teikyo Heisei University

Fish oil contains omega-3 polyunsaturated fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Exhaustive or unaccustomed exercises cause muscle fatigue and delayed onset muscle soreness (DOMS), resulting in decreased exercise performance. A recent our study confirmed that the intake of EPA and DHA inhibited the muscle strength loss, limited range of motion (ROM), development of DOMS, and increase in serum interleukin (IL)-6 levels after 30 maximal eccentric contractions (ECCs) of elbow flexors. Although our previous study demonstrated that EPA and DHA supplementation attenuates muscle strength loss after ECCs, the detailed mechanism was unclear. Hence, the present study focused on muscle stiffness in concomitant with muscle strength and joint flexibility loss, clarifying of the further mechanism. Purpose: This study aimed to investigate the effect of supplementation of fish oil rich in EPA and DHA on the damage of the biceps brachii after ECCs of the elbow flexors, particularly focusing on muscle stiffness. Methods: Sixteen men were included in this double-blind, placebo-controlled, parallel design study. The participants were randomly assigned to the EPA and DHA supplement group (EPA, n = 8) and placebo group (PL, n = 8). They consumed either EPA 600 mg and DHA 260 mg per day or placebo supplement for 8 weeks prior to exercise. Moreover, they performed 6 sets of 10 ECCs at 100% maximal voluntary contraction (MVC) using a dumbbell. Changes in MVC torque, range of motion (ROM), upper arm circumference, muscle soreness, muscle echo intensity, and muscle stiffness were assessed before exercise; immediately after exercise; and 1, 2, and 5 days after exercise. Results: MVC torque and ROM were significantly higher in the EPA group than in the PL group after ECCs (p < 0.05). Muscle soreness, upper arm circumference, and muscle echo intensity were significantly higher in the PL group than in the EPA group after ECCs (p < 0.05). In addition, muscle stiffness at 150° was significantly higher in the PL group than in the EPA group immediately after ECCs (p < 0.05). Conclusion: The present study showed that the supplementation of EPA and DHA has a positive role in inhibiting muscle stiffness after ECCs. Practical Applications: Our findings of the beneficial effects of EPA and DHA supplementation are important for applied sport scientists, nutritionists, and strength and conditioning professionals and could help them to design better nutritional interventions for preventing muscle damage and stiffness after exercise.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

The Effect of Recovery Beverages on Cycle Sprint Performance Within Trained Individuals

T. Farney,1 R. Kowalsky,2 D. Salazar,2 and C. Hearon2

1Texas A&M University—Kingsville; and 2Texas A&M University-Kingsville

Purpose: The focus of this investigation was to examine the effects of vinegar and sugar upon cycle sprint performance in trained individuals. Methods: Twenty-two participants (males = 15; females = 7) (age: 24.5 ± 5.9 years; stature: 1.69 ± 0.609 m; & mass: 74.8 ± 12.4 kg) visited the lab on 4 different days all separated by one week. The treatments were consumed in a randomized order and included: 1) 29 ml of commercially available acetic acid (vinegar) (VIN) along with 451 ml of water, 2) 39 g of sucrose (SUG) along with 441 ml of water, 3) 29 ml vinegar and 39 g of sucrose (CBO) along with 412 ml of water, or 4) 480 ml of water alone (H2O). Prior to testing sessions, participants performed a graded exercise test on a cycle ergometer to determine maximal power wattage to be used for testing. For all experimental trials, participants performed 3 cycle sprints to failure and one steady state cycle bout. Each cycle sprint include participants cycling for 1 minute at 150% of their recorded maximal power output while at a cadence of 100 rpm. There was a 2 minutes rest between each sprint, and failure was determined when participants couldn't finish the full minute or cadenced dropped below 100 rpm for 10 contiguous seconds. Following the first cycle sprints to failure, participants then cycled for 30 minutes at 50% of their recorded maximal power output. At the completion of the steady state cycling, participants then performed the second set of cycle sprints to failure. From here, participants consumed the designated recovery beverage, and then rested quietly for 90 minutes. Once the rest period was completed, participants performed the third set of cycle sprints to failure. Heart rate (HR) was recorded at the end of each full 1 minute sprint, and when failure to sprint occurred. Total amount of sprint time (ST) for each set of sprints was used in analysis. Results: There were no treatment or interaction effects (p > 0.05) for ST or HR when comparing sprint 1 to sprint 3. There was a time effect (p = 0.001) when comparing sprint 1 to sprint 3 with ST 3 being significantly lower (140 ± 39 seconds) to ST 1 (183 ± 36 seconds). Additionally, there was time effect (p = 0.001) when comparing HR ST 1 to HR ST 3 with HR ST 3 being significantly lower (165 ± 13 bpm) than HR ST 1 (170 ± 12 bpm). Lastly, there was a statistically significant decrease in ST and HR (p = 0.001) from ST 1 (183 ± 43 seconds; 170 ± 12 bpm) to ST 2 (111 ± 56 seconds; 173 ± 13 bpm), respectively. Conclusion: The addition of acetic acid or sucrose was ineffective in improving cycle sprinting when performing 3 cycle sprints to failure. Total time of sprinting was not impacted when consuming either vinegar or sugar alone, or in combination. Additionally, HR was not altered by either supplement. Practical Applications: Acetic acid has been reported to improve performance due to its ability to increase glycogen replenishment when taken with a carbohydrate. The findings within this investigation could have been a result of not enough work load being performed. Additionally, participants may not have fully depleted glycogen stores in order to notice an impact with acetic acid supplementation. Future research should focus on the work load being performed and the degree of glycogen depletion when investigating acetic acid supplementation.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Sports Drink Ingestion Inflates Heart Rate Variability: Implications for Pre-training Measures

C. Ragsdale, J. Ellis, J. Phelps, N. Foster, and A. Flatt

Georgia Southern University

Sports teams acquire pre-training heart rate variability (HRV) in athletes to assess training status. HHowever, pre-training hydration practices may acutely affect cardiovascular dynamics and thus obscure resting-HRV. This creates a methodological concern for staff because coolers filled with bottles of water and sports drinks are typically made available for athletes in the hours before training. Purpose: To determine the effects of 591 ml of cold water and sports drink ingestion on HRV. Methods: Recreationally-trained, college-age men (n = 6) and women (n = 3) volunteered for this study. On separate days after an overnight fast, subjects ingested 591 ml of water, a sports drink or control (10 ml water) in a randomized order. R-R intervals were recorded for 10 minutes pre- and for an additional 25 minutes post-fluid ingestion. Beverages were consumed within a 2-min window. The natural logarithm of the root-mean square of successive R-R intervals (LnRMSSD) was calculated from min 5–10 pre-ingestion to establish baseline (T1) and again at 5–10 minutes post- (T2) and 20–25 minutes post-fluid ingestion (T3). A linear mixed model and Cohen's effect sizes (ES) were used to examine variation in LnRMSSD responses. Results: A significant condition × time interaction was observed (p < 0.0001). LnRMSSD did not change across time for control (T1 = 4.19 ± 0.36, T2 = 4.17 ± 0.39, T3 = 4.27 ± 0.31, p > 0.05). LnRMSSD increased following both water (T2 = 4.52 ± 0.26, ES = 1.06) and sports drink (T2 = 4.66 ± 0.38, ES = 1.27) ingestion at T2 (p < 0.05). LnRMSSD remained significantly elevated at T3 for sports drink (T3 = 4.54 ± 0.37, ES = 0.97) relative to control (p < 0.05). Though not statistically significant, ES analysis revealed that LnRMSSD at T2 for the sports drink condition was greater than water (ES = 0.83, p > 0.05). In addition, water at T3 (4.49 ± 0.31, ES = 0.64, p > 0.05) was greater than control at T3. Conclusion: Water and sports drink ingestion caused significant increases in LnRMSSD at 5–10 minutes post-ingestion. The effects persisted to 20–25 minutes post-ingestion, primarily for the sports drink condition. Practical Applications: Fatigue-related decrements in LnRMSSD may be masked by acute fluid ingestion and thus result in a misinterpretation of training status. For example, elevated HRV typically indicates a positive coping and recovery response to training, reflecting high cardiac-parasympathetic activity. However, the effects of fluid ingestion may produce a false positive by transiently inflating an athletes HRV, masking their true resting-state autonomic activity. Therefore, practitioners should control for fluid ingestion when obtaining HRV measures prior to training. Since LnRMSSD remained above baseline at 25 minutes post-ingestion, further investigation using extended post-ingestion follow-up is needed to determine how long effects persist.

Thursday, July 11, 2019, 2:00 pm–3:30 pm

Effect of Supplementary Plyometric Training to Resistance Training in High School Boys Basketball Athletes

M. Tate, J. Martin, and M. Fyock-Martin

George Mason University

Introduction: Vertical jump (VJ) has been accepted as a valid measure of lower body power and has a strong relationship with athletic performance in many sports. Numerous studies have investigated the effect of resistance training or plyometric training alone on VJ. Resistance training and plyometric have both been found to significantly increase VJ in healthy, trained young men. Limited evidence exists examining the effects of a supplementary plyometric training to a resistance training program. A majority of studies have focused on college age athletes; however, many high school age athletes desire to increase VJ ability for the purpose of improving athletic performance. Purpose: To examine the effects of supplementary plyometric training in a resistance training program, on VJ in high school basketball players. Methods: Sixteen male high school basketball playersparticipated in the 10-week, 2-group cohort study. Participants were assigned to a group based on the high school they were enrolled at. One group participated in resistance training (RT) only (age: 15.6 ± 1.3 years; weight: 66.6 ± 11.4 kg). The second group included the addition of plyometric training to the resistance training (PLY + RT; age: 14.8 ± 1.0 years; weight: 69.7 ± 10.6 kg). VJ testing was conducted using the Vertec on the first day of training for both groups, and during the last week of the program. Peak power was computed using the X Harman (1991) equation. Statistical analyses were performed to investigate the effects of the RT and PLY + RT programs on VJ performance. An independent samples t-test (p < 0.05) was performed to test for significant differences in the change in jumping performance between the training groups. Cohen's d effect sizes (ES) of the changes were computed to compare the magnitude of the changes. Results: The results showed that there was not a statistically significant change in VJ between the groups (p > 0.80; ES = 0.11). RT and PLY + RT both increased vertical jump (RT: 8.32 ± 5.03 cm; PLY + RT: 8.39 ± 5.03 cm). No significant differences (p > 0.6; ES = 0.27) in peak power between the groups were found (RT: 461 ± 260 W; PLY + RT: 540 ± 329 W). Conclusion: Each program resulted in an increase in VJ and peak power; however, no statistically significant difference between programs were found in regards to either measure. While both groups were statistically similar in VJ and peak power measures at the start of the study there was a large range of these values within the groups. This may be due to the training age of participants as some subjects had previous resistance training experience. Practical Applications: The results of this study suggest that supplementary plyometric training will not produce a higher vertical jump than a strictly strength training program in high school male basketball players. While plyometric training did not result in greater improvements, there are benefits that should be considered when choosing whether to implement plyometric training. Plyometric training mimics similar in-game movements, such as jumping and change of direction, and may reduce injuries from landing from practicing proper technique.

Friday, July 12, 2019, 8:30 am–8:45 am

Are Mentally Tough Female Athletes Grittier? Collegiate Female Athletes′ Perspectives From the Weight Room

V. Smith1 and E. Moore2

1Wayne State Universiy; and 2Wayne State University

Mental toughness (MT) and grit are 2 psychological characteristics that strength and conditioning coaches (SCC) use to describe athletes in a positive manner. Purpose: Examine the reliability and validity relationships between multiple measures of MT and grit in the strength and conditioning (S&C) context over time among female collegiate athletes. Methods: Sixty-three female Division I college athletes' (Age = 19 years ± 1.23 years) were surveyed prior to beginning their season's competitions (T1) and approximately 12 weeks later (T2). Each survey took roughly 15 minutes to complete and was administered before/after working with their SCC. The survey included 3 MT questionnaires: implicit theory mental toughness (MT-Fixed and MT-Malleable), mental toughness index (MTI), and sports mental toughness questionnaire (SMTQ); grit, and goal orientations (egoGO and taskGO). Reliability was assessed with Cronbach's alpha coefficient. Means were calculated and examined for differences over time. Correlations assessed within time relationships, test-retest reliability, and cross-time relationships. To examine the predictive relationships of these variables over time multiple linear regressions were performed. Results: All measured variables met the Cronbach alpha coefficient recommended guideline of at least 0.70 for reliability. Overall, the athletes reported relatively moderate levels of MT and grit. Athletes' most agreed with the concept of MT as malleable. The correlations (rs = −0.36 and −0.63) between MT-fixed and MT-malleable were lower than expected. The only other MT variables correlated with each other within time were SMTQ and MTI (rs = 0.64 and 0.60). T1_Grit was significantly, negatively correlated with MT-Malleable (r = −0.30), MTI (r = −0.39), and SMTQ (r = −0.45). Across time, there were only 7 significant correlations: ITMT with itself (r = 0.34), MTI with itself (r = 0.41), SMTQ with itself (r = 0.49), grit with itself (r = 0.44), and ego GO with itself (r = 0.36), plus T2_SMTQ with T1_MTI (r = 0.42) and with T1_Grit (r = −0.39). Linear regressions revealed that the only T2 variables not significantly predicted by their T1 values were MT-Fixed and MT-Malleable. The rest of the variables' T1 values predicted no more than 22% of the respective T2 variable's variance. Further, only T2_Grit was predicted by more than itself from T1; specifically, task GO (β = 0.42, p = 0.04) and SMTQ (β = 0.50, p = 0.02). T2_Grit was the only variable to significantly change from T1 (Mdiff = 0.48, p < 0.001). Conclusion: Although the measures of MT and grit showed acceptable reliability, they had poor validity. This was illustrated by the few and low correlations between different variables within or between timepoints. Most notably, the test-retest correlations for the variables with themselves between T1 and T2 did not reach even moderate levels. These results illustrate the inconsistency with how MT is defined in the literature, and suggests that grit is not the same thing as MT. Practical Applications: If SCCs want to measure MT or grit, they are 2 different characteristics. However, regardless if a measure is called MT or grit, what is most important for SCCs is to carefully examine the items of the different measures to ensure the SCCs select the one measuring what they value. Together, these results suggest that for both researchers and SCC interested in MT or grit, further work is needed to develop reliable and valid S&C specific measures.

Friday, July 12, 2019, 8:45 am–9:00 am

Comparison of Contralateral Elbow Flexor Rate of Force Development After Separate Concentric and Eccentric Exercise to Failure

W. Miller, X. Ye, and S. Jeon

University of Mississippi

Decreased rate of force development (RFD) post-exercise is an important indicator for performance reduction in sports and daily life, and it has been previously shown in both the exercised and non-exercised limbs. Explanations for reduced RFD in the non-exercised limb (i.e., crossover) are plausibly due to centrally-mediated factors. While many studies have focused on the crossover effect of fatigue with a wide variety of muscle action types (e.g., isotonic, isometric, isokinetic), few focused on the changes in RFD in the contralateral (unexercised) limb. Purpose: The purpose of this study was to examine how concentric and eccentric muscle actions to failure in the dominant arm elbow flexor (EF) would affect RFD in the contralateral EF. Methods: Fifteen subjects consented to participate in the randomized crossover within-subjects design. Participants reported to the lab for 10 visits (i.e., familiarization, concentric, eccentric, and control) followed by 24 and 48 hours follow-up visits. Participants performed concentric and eccentric dominant arm dumbbell exercise for 6 sets to task failure with loads corresponding to 25 and 30% of maximal voluntary isometric contraction (MVIC) strength, respectively. Exercise was set at a cadence of 1-second up/down for each repetition and the investigator manually removed and replaced the dumbbell accordingly. The control visit included no exercise. Dominant (exercised) and non-dominant (contralateral) RFD at the time interval of 0–50 (RFD50) ms from onset was measured at pre-, immediate-post, 24hr- and 48hr-post for all visits. Two-way ANOVAs for the dominant (exercised) and non-dominant (non-exercised) arm (condition [eccentric, concentric, control] ´ time [RFD50] were performed with an a set at 0.05. Results: Significant main effects for time at RFD50 were revealed for the non-dominant arm. Follow-up tests revealed significantly lower RFD for immediate-post compared to 48hr-post (mean ± standard error (SE): 443.16 ± 138.76 vs. 556.14 vs. 144.53 Nm·s−1). Significant main effects for condition and time were revealed for dominant arm RFD50. Follow-up tests showed significant lower RFD (collapsed across condition) for immediate-post compared to pre (mean ± SE; immediate-post vs. pre: 297.65 ± 82.51 vs. 570.69 ± 153.18 Nm·s−1) and to 24 hr-post (mean ± SE; immediate-post vs. 24 hr-post: 297.65 ± 82.51 vs. 474.29 vs. 117.61 Nm·s−1). Conclusion: For early onset RFD the non dominant arm was unaffected by dominant arm exercise, and regardless of condition, early onset RFD was decreased immediate-post and remained decreased for up to 24 hr-post in the dominant arm. Practical Applications: Gaining a greater understanding of how differing exercise modes affect RFD has implications for several populations (e.g., young, old, athlete, non-athlete). This study provides specific evidence that concentric and eccentric exercise cause similar decreases in early onset RFD directly after exercise and up to 24 hours after in the young non-athletic population. Thus, when designing a resistance training program for this population trainers and practitioners can incorporate specific eccentric exercise for enhancing strength with the understanding that it will affect rapid force production ability similar to concentric exercise.

Friday, July 12, 2019, 9:00 am–9:15 am

Slopes of the Motor Unit Action Potential Amplitude-Recruitment Threshold Relationships Correlates With Isokinetic Peak Torque at 2 Velocities

M. Parra,1 J. Miller,2 M. Hatcher,2 S. Sontag,2 M. Hermes,2 and T. Herda2

1University of Kansas; and 2University of Kansas

Purpose: To examine the association between the slopes of the motor unit action potential amplitudes (MUAPAMPS)-recruitment threshold (RT) relationships and isokinetic peak torque. Methods: Twelve healthy, recreationally active males (age = 20.7 ± 2.6 years; height = 183.8 ± 5.7 cm; weight = 88.5 ± 11.4 kg) volunteered for this investigation. A 5 pin electromyographic (EMG) sensor was placed over the vastus lateralis (VL). Each participant performed 2 isometric maximal voluntary contractions (MVCs) of the leg extensors. The highest peak torque (PT) of the contractions was used to normalize trapezoid muscle actions at 70% MVC. The surface EMG signals were decomposed to extract MUAPAMP and corresponding RTs. Only MUs decomposed with accuracies >90% from the reconstruct-and-test and possessed stable AP waveforms via a spike trigger average procedure were included for analysis. Linear regressions were performed to determine the slopes of the MUAPAMP-RT relationships separately for each subject. Each subject performed 3 isokinetic muscle actions at 1.05 and 3.14 rad·s−1 (PT1.05 and PT3.14). Isokinetic PT was calculated as the highest mean value over a 25 ms epoch during the load range with the average of the 3 trials used for statistical purposes. Pearson product moment correlations were used to determine possible significance relationships between isokinetic PT (PT1.05 and PT3.14) and the slopes of the MUAPAMP-RT relationships. Alpha was set at 0.05. Results: The average RTs of observed MUs from the 70% MVC were 24.7–57.5% MVC and all relationships were significant (r = 0.845 ± 0.163) with positive slopes (0.0051 ± 0.0030 mV/%MVC) for each subject. The isokinetic PT values were 209.6 ± 30.7 Nm and 153.5 ± 36.8 Nm for PT1.05 and PT3.14, respectively. There were positive correlations between the slopes of the MUAPAMP-RT relationships and PT1.05 (r = 0.579; p = 0.048) and PT3.14 (r = 0.716; p = 0.009). Conclusion: The slopes of the MUAPAMP-RT relationships explained a significant portion of the variance in isokinetic PT at 1.05 and 3.14 rad·s−1. The greater slopes indicated recruitment of larger MUs with increments in RTs. Thus, recruitment of relatively larger higher-threshold MUs during a 70% MVC were associated with PT recorded during the isokinetic muscle actions. Previously, the slopes of MUAPAMP-RT relationships were positively correlated with muscle cross-sectional area. It is plausible that individuals with greater slopes for the MUAPAMP-RT relationships possessed greater muscle fiber diameters of higher-threshold MUs that leads to greater torque development during isokinetic muscle actions. Practical Applications: The sizes of higher-threshold MUs, or the diameter of muscle fibers that comprise the MUs, are of importance for maximal muscular strength and power. Increasing the sizes of higher-threshold MUs via high-intensity resistance training may partially explain the subsequent increases in muscular strength and power.

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Figure 1.:
The plotted relationships of the isokinetic PT (Nm) at 1.05 and 3.14 rad·s−1 vs. the slopes of the MUAPAMP-RT relationships with the line of best fit from the linear regression model presented.

Friday, July 12, 2019, 9:15 am–9:30 am

Sex-Specific Neuromuscular and Force Responses Following a Fatiguing Task Anchored to Low and High Perceptions of Effort

J. Keller,1 T. Housh, E. Hill,2 C. Smith, R. Schmidt, and G. Johnson3

1University of Nebraska-Lincoln; 2University of Nebraska Lincoln; and 3University of Nebraska—Lincoln

Performance fatigability (PF) is defined as the magnitude of change in maximal voluntary isometric contraction (MVIC) following a fatiguing task. It has been reported that there are sex-and intensity-related differences in the physiological factors that contribute to PF. Purpose: The purpose of this study was to examine sex- and intensity-related differences in the neuromuscular and force production patterns of responses during sustained isometric muscle actions anchored to RPE = 2 and 8. Methods: Twenty college-aged adults (10 men, 10 women) performed sustained, isometric leg extension muscle actions at RPE = 2 and RPE = 8 for a maximal duration of 5-minute. The MVICs were performed prior to (pretest) and following (posttest) the sustained isometric muscle actions. Electromyographic (EMG) and mechanomyographic (MMG) signals were recorded from the vastus lateralis muscle of the dominant leg. The resulting values were normalized to the respective values during the MVICs, and EMG amplitude (AMP), EMG mean power frequency (MPF), MMG AMP, MMG MPF, and force values were calculated every 5% of the actual time-limit. A 2 (Sex: Men, Women) × 2 (RPE: 2.8) × 2 (Test: Pretest, Posttest) mixed factorial ANOVA was used to examine PF in men and women. Polynomial regression (linear and quadratic) analyses were used to examine the neuromuscular parameters and force production vs. time relationships during the sustained isometric muscle actions. Results: For absolute MVIC force, there was a significant (p = 0.002; = 0.407) 3-way interaction, and the men exhibited a greater (p = 0.02; d = 0.85) PF at RPE = 2 than RPE = 8 (RPE = 2: 62.4 ± 14.4 kg to 43.1 ± 11.5 kg; RPE = 8: 63.5 ± 12.7 kg to 54.4 ± 14.8 kg). The women exhibited a significant decrease in MVIC pretest to posttest (45.7 ± 4.6 kg to 39.9 ± 5.2 kg; p < 0.001, d = 1.2), but no difference in PF between RPE = 2 and RPE = 8. For neuromuscular and force production patterns of responses, at RPE = 2, the men demonstrated significant (p < 0.001), negative, quadratic EMG AMP, EMG MPF, MMG MPF, and force vs. time relationships and a significant (p < 0.001), positive, quadratic increase in MMG AMP vs. time relationship. The women exhibited significant (p < 0.001), negative, quadratic EMG AMP and force vs. time relationships as well as a significant (p = 0.04), negative linear EMG MPF vs. time relationship. At RPE = 8, both the men and women exhibited significant (p < 0.001), negative, quadratic EMG MPF and force vs. time relationships. Conclusion: The men and women demonstrated PF following the sustained isometric muscle actions anchored to RPE = 2 and RPE = 8, but the men exhibited a greater magnitude of PF following RPE = 2 than RPE = 8, while the women had the same PF at RPE = 2 and RPE = 8. In addition, there were sex-related differences in the neuromuscular patterns of responses at RPE = 2, but not RPE = 8. Thus, perhaps men and women utilize similar mechanisms of fatigue at high intensities, but not at lower intensities. Collectively, these findings suggested that the motor unit activation strategies and PF differ according to sex and intensity. Practical Applications: The results of the current study provided insight into the underlying mechanisms of perceived exertion and PF as well as the sex-related differences in adjustments of motor unit activation strategies needed to maintain an RPE. These results contribute to the understanding RPE-based resistance exercise responses and suggest a need for sex-specific guidelines across the RPE scale.

Friday, July 12, 2019, 9:30 am–9:45 am

Larger Motor Units Are Recruited for High Intensity Contractions Than for Fatiguing Moderate Intensity Contractions

J. Miller,1 J. Lippman,2 M. Trevino, M. Parra,3 and T. Herda1

1University of Kansas; 2University of Illinois at Chicago; and 3University of Kansas

Purpose: To compare excitation and action potential amplitudes (APAMP) of motor units (MU) recruited during a high intensity contraction to the last moderate intensity contraction performed during a fatiguing protocol. Methods: Nine subjects (7 males, 2 females, age = 22.78 ± 4.15 years, height = 173.78 ± 14.19 cm, mass = 87.39 ± 21.19 kg) completed 3 isometric maximum voluntary contractions (MVC), one 90% MVC, and repetitive 50% MVCs until fatigue. The isometric contractions at 90 and 50% MVC were composed of a linearly increasing force segment (10% MVC/s), a steady force segment (12 seconds), and a linearly decreasing force segment (−10% MVC/s). The repetitive 50% MVC fatiguing protocol was terminated when the subject could no longer maintain the required 50% MVC force. During the 90 and 50% MVCs, surface EMG was recorded from the vastus lateralis and decomposed into action potential trains for individual MUs. MU action potential amplitudes (MUAPAMP), recruitment thresholds (RT), mean firing rates (MFR), and EMG root mean squared amplitude were calculated during the steady force epoch for each contraction. For each subject, linear MFR vs. RT and MUAPAMP vs. RT relationships were calculated for the 90% MVC (REP90), and for the last (REPL) 50% MVC completed. Dependent samples t-tests and Cohen's d effect sizes analyzed potential differences between REPL and REP90 for EMG amplitude, mean and maximum APAMPS of observed MUs for each contraction, predicted MFRs at 40% MVC, and the slopes and y-intercepts of the MFR vs. RT and MUAPAMP vs. RT relationships. Results: There were no differences between REPL and REP90 for slopes (P = 0.133, d = 0.96, REPL = −0.53 ± 0.21 pps/%MVC, REP90 = −0.38 ± 0.06 pps/%MVC) or y-intercepts (P = 0.783, d = 0.16 REPL = 32.5 ± 11.3 pps, REP90 = 33.8 ± 3.89 pps) of the MFR vs. RT relationships, although predicted MFRs for MUs recruited at 40% MVC were greater (P = 0.005, d = 2.34) during REP90 (18.5 ± 2.71 pps) than REPL (11.1 ± 3.48 pps). No differences were observed between REPL and REP90 for the slopes (P = 0.158, d = 0.69, REPL = 0.006 ± 0.003 mV/%MVC, REP90 = 0.009 ± 0.006 mV/%MVC) or y-intercepts (P = 0.059, d = 1.42, REPL = −0.032 ± 0.086 mV, REP90 = −0.258 ± 0.210 mV) of the MUAPAMP vs. RT relationships, however, mean (P = 0.038, d = 0.83, REPL = 0.178 ± 0.067 mV, REP90 = 0.263 ± 0.128 mV) and maximum (P = 0.008, d = 1.07, REPL = 0.320 ± 0.127 mV, REP90 = 0.520 ± 0.234 mV) APAMPS of observed MUs were greater during REP90 than REPL. In addition, a t-test indicated no difference in EMG amplitude between contractions (P = 0.076), but a medium effect size (d = 0.66) indicated greater EMG amplitude for REP90 (101 ± 61.1 mV) than REPL (69.6 ± 27.2 mV). Conclusion: Firing rates of higher-threshold MUs and MUAPAMPS were greater for the 90% MVC than the last 50% MVC, and a moderate effect size indicated EMG amplitude was greater for the 90% MVC. Performing an isometric trapezoidal 90% MVC required greater excitation and recruitment of larger MUs than the last 50% MVC performed during the fatiguing protocol. Practical Applications: Recruitment of larger MUs and greater excitation were observed for a high intensity contraction in comparison to the last moderate intensity contraction performed during a fatiguing protocol. These findings suggest strength and conditioning coaches should rely on high intensity training rather than moderate intensity to fatigue paradigms to activate and stress the entire motoneuron pool.

Friday, July 12, 2019, 9:45 am–10:00 am

Functional Stability in Collegiate Lacrosse Athletes Over a Non-Traditional Season

C. Rosenborough, S. Collins, E. Smith, and T. Bowman

University of Lynchburg

Functional movement may change in lacrosse athletes due to stress on the body from sport. Stability may change over the course of a season as functional movement is altered, resulting in the possibility of increased risk of injury later in a season due to compensatory patterns or stability changes. This can affect proprioception, balance and range of motion (ROM). Purpose: To examine the effects of a non-traditional lacrosse fall season on functional movement and stability in both male and female collegiate lacrosse athletes. Methods: We recruited 50 male (age = 19.38 ± 1.24 years, height = 182.63 ± 6.16 cm, mass = 82.37 ± 8.46 kg) and 22 female (age = 19.68 ± 1.17 years, height = 165.10 ± 6.88 cm, mass = 64.09 ± 8.72 kg) volunteers from National Collegiate Athletic Association Division III lacrosse teams for the study. Independent variable was time (pre, post). Main outcome measures included pre- and post-season upper and lower extremity balance measurements as well as dorsiflexion (right, left) range of motion (ROM) via goniometer. Data files were split by sex then analyzed using a 1-way repeated measure ANOVA. Results: Time significantly improved right arm scores from preseason (mean = 78.21 + 2.59) to postseason (mean = 81.21 ± 2.46; F1,21 = 4.55, p = 0.05, η2 = 0.18) for females but not for males (F1,49 = 0.52, p = 0.48, η2 = 0.01, 1-β = 0.11). Female right leg scores improved significantly from preseason (mean = 98.67 ± 1.74) to postseason (mean = 101.62 ± 1.73; F1,21 = 8.69, p = 0.01, η2 = 0.29). Male right leg scores also improved significantly from preseason (mean = 102.47 ± 1.31) to postseason (mean = 105.64 ± 1.54; F1,49 = 11.78, p = 0.001, η2 = 0.19). For the left leg, time significantly improved male scores from preseason (mean = 102.41 ± 1.29) to postseason (mean = 104.32 ± 1.37; F1,49 = 5.08, p = 0.03, η2 = 0.09) but not female scores (F1,21 = 3.02, p = 0.10, η2 = 0.13, 1-β = 0.38). Time significantly decreased male right dorsiflexion ROM from preseason (mean = 34.36 cm ± 1.09) to postseason (mean = 30.26 cm ± 0.90; F1,49 = 24.98, p < 0.001, η2 = 0.34) as well as left dorsiflexion ROM from preseason (mean = 34.70 cm ± 0.85) to postseason (mean = 30.34 cm ± 0.74; F1,49 = 34.21, p < 0.001, η2 = 0.41) but not female for right (F1,21 = 0.22, p = 0.64, η2 = 0.01, 1-β = 0.07) and left dorsiflexion ROM (F1,21 = 0.74, p = 0.40, η2 = 0.03, 1-β = 0.13). Conclusion: Our findings indicate that there are several significant changes in stability and ankle dorsiflexion ROM over the course of a season in several key functional areas. Practical Applications: Clinicians should be aware of male lower extremity stability improvements with concurrent decreases in dorsiflexion over an athletic season. Stability changes may differ from male to female as female dorsiflexion ROM did not change. Changes in joint stability may alter injury risk; therefore, dorsiflexion ROM should be considered when developing in-season strength, conditioning and flexibility programs for male lacrosse athletes.

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Figure 1.:
Dorsiflexion Change Over Time. This graph illustrates the change in both right and left dorsiflexion ROM for males and females from preseason and postseason.

Friday, July 12, 2019, 10:15 am–10:30 am

Drop Vertical Jump Landing Ground Reaction Force Metrics Identify Elite Male Youth Soccer Players at Increased Risk of Non-Contact Knee Injury

J. Pedley,1 R. Lloyd, P. Read,2 I. Moore, M. De Ste Croix,3 G. Myer, and J. Oliver

1Cardiff Metropolitan University; 2Aspetar; and 3University of Gloucestershire

Introduction: The drop vertical jump (DVJ) is a widely researched jump-landing injury screening assessment. Current literature is focused on female athletes and movement kinematics with limited characterization of ground reaction force characteristics which drive landing mechanics during the stretch-shortening cycle (SSC) of the DVJ. External load is also an underlying knee injury mechanism and therefore, enhanced characterization of forces in the early stages of ground contact that relate to injury mechanism could enhance current injury risk screening methods. Purpose: To prospectively examine the association between DVJ ground reaction force metrics and knee injury risk in elite male youth soccer players. Methods: 266 elite male youth soccer players (Age: 14.0 ± 2.0 years; Body Mass: 52.3 ± 14.0 kg; Stature: 162.3 cm ± 15.2 cm; Maturity Offset: −0.2 ± 1.9 years) from the academies of professional English soccer clubs, participated in this prospective cohort study. Participants completed a DVJ on a force plate recording at 1,000 Hz and were monitored for non-contact knee injury incidence for one competitive season. Ground reaction force data were analysed and converted to z-scores prior to conducting univariate and multivariate binary logistic regression. Associations between kinetic variables and risk of sustaining a non-contact knee injury were determined while controlling for maturity offset. Receiver operator curve analysis was performed to determine cut-scores for optimal sensitivity and specificity for the predictor variables. Results: Univariate analysis revealed greater peak landing force (PLF) (OR = 1.81, 1.03–3.19; 79% sensitivity, 48% specificity), greater landing: take-off peak ratio (LTPRatio) (OR = 1.59, 1.10–2.19; 42% sensitivity, 87% specificity), reduced relative concentric work (RCW) (OR = 0.53, 0.28–0.99; 90% sensitivity, 34% specificity), greater relative stiffness (OR = 1.68, 1.13–2.52; 5% sensitivity, 99% specificity) and greater peak vertical ground reaction force (PF) (OR = 1.89, 1.04–3.45; 58% sensitivity, 68% specificity) were significantly associated with increased risk of non-contact knee injury. Performance measures including reactive strength index (RSI), jump height (JH) and ground contact time (GCT) were not significantly associated with knee injury (all p > 0.2). When controlled for other variables, LTPRatio (OR = 1.61, 1.14–2.30) and relative stiffness (OR = 1.81, 1.07–3.08) still presented a significant association with risk of suffering an acute non-contact knee injury. Conclusion: Outcome measures such as RSI, JH and GCT appear to have no association with knee injury risk, however, greater LTPRatio and PLF were associated with knee injury risk suggesting that it is the landing strategy deployed by an athlete that is of greater importance than the overall performance in this context. These variables appear sufficiently sensitive to differentiate elite male youth soccer players at increased risk of knee injury. Practical Applications: High landing forces in the early stages of GCT are associated with greater risk of knee injury. Ground reaction force profiling could help practitioners to determine whether an athlete should focus on absorbing force more effectively over a longer period of time, or whether they are competent enough to direct attention towards reducing GCT. Only monitoring performance measures such as RSI, GCT and JH might cause practitioners to overlook injurious landing strategies.

Friday, July 12, 2019, 10:30 am–2:00 am

Supine and Standing Heart Rate Variability Responses to Training in Womens Soccer Players

B. Oddi,1 M. Christiani,2 and A. Flatt2

1California University of PA; and 2Georgia Southern University

Heart rate variability (HRV) is a popular recovery status marker among sports teams. HRV is traditionally measured in the supine position, but the standing position provides a small physiological challenge that requires autonomic modulation of heat rate and vessel diameter to augment blood pressure and flow to adapt to the upright position. Thus, capturing HRV after standing upright may provide greater sensitivity to previous-day training, assuming that an unrecovered athlete will display a more prolonged or exaggerated stress response to standing. Purpose: To assess supine and standing HRV responses to standardized offseason training in collegiate women's soccer players. A secondary aim was to assess within-subjects correlations between supine and standing measures. Methods: A women's soccer team (n = 12, age = 22 ± 2 years; height = 165 ± 6 cm; weight = 61 ± 6 kg) participated in this study. Throughout 4 non-consecutive weeks throughout the offseason, players performed resistance training, soccer practice, and cardiorespiratory conditioning on Mondays and Thursdays. Soccer practices only were also held on Wednesdays and Fridays. Players recorded ultra-short, natural logarithm of the root mean square of successive R-R intervals multiplied by 20, LnRMSSD) in the supine and standing position, daily after waking with a validated mobile device. Training load from each session was quantified via the session rating of perceived exertion method (sRPE). Linear mixed models and Cohen's effect sizes were used to assess variation in outcome variables. Pearson's correlations were used to quantify within-subjects relationships between supine and standing LnRMSSD. Results: The sRPE from Mondays and Thursdays was greater than Wednesdays and Fridays (p < 0.05, ES = 2.95–3.25). Standing LnRMSSD on Mondays was greater than Tuesdays and Fridays (p < 0.05, ES = 0.48–0.52). No main effect was observed for supine LnRMSSD (p = 0.10, ES = 0.10–0.49). Mean ± 95% confidence interval for supine and standing LnRMSSD and sRPE are displayed in Figure 1. Within-subjects correlations between supine and standing LnRMSSD ranged from r = −0.165–0.625, with statistical significance (p < 0.05) achieved for only 4 players. Conclusion: Significant decrements in standing, but not supine LnRMSSD were observed following days with the greatest training load. Supine LnRMSSD measures were not consistent predictors of standing measures. Practical Applications: When monitoring HRV for the purpose of assessing responses to previous-day training, standing measures may be preferred over supine measures. Practitioners should be aware that supine and standing measures do not show consistent relationships and therefore should not be used interchangeably.

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Figure 1.:
Mean ± 95% confidence interval for supine and standing LnRMSSD and sRPE. *Different from Monday (p < 0.05). ¥Different from Monday and Thursday (p < 0.05).

Friday, July 12, 2019, 10:30 am–10:45 am

ACL Injuries Increase Balance and Jump-Landing Asymmetries in Collegiate Athletes: A Longitudinal Study With Pre-injury Assessments

N. Bordelon,1 J. Layer,2 S. LaCroix,2 M. Critchley,3 and B. Dai

1Auburn University; 2University of Wyoming; and 3University of Calgary

Introduction: Anterior cruciate ligament (ACL) tears are one of the most severe lower extremity injuries amongst collegiate athletes. Following an ACL injury, individuals typically decrease strength and balance performance and increase lower extremity asymmetry. ACL re-injury rates are very high despite surgical reconstruction and rehabilitation, so it is imperative to understand the injury mechanism and develop prevention strategies. Purpose: To quantify the effect of ACL injuries and reconstruction on performance and bilateral asymmetries in a lower extremity reaching test and a counter-movement jump-landing (CMVJ) test in collegiate athletes. Methodology: The current study was a continuation of a previous study, where approximately 500 collegiate athletes from a National Collegiate Athletic Association Division I university performed baseline assessments. In the follow-up, 8 athletes (5 men's American Football, 1 women's soccer, 1 women's basketball, and 1 women's volleyball; age: 19.4 ± 1.2 y; height: 1.83 ± 0.10 m; weight: 85.2 ± 16.5 kg) sustained an ACL injury and were included in the study. All participants were treated with a standard rehabilitation program under team physicians and athletic trainers. Athletes performed baseline lower extremity reaching and CMVJ tests prior to their injury. They also performed a lower extremity reaching test 3 and 6 months post-ACL reconstruction surgeries and a CMVJ test 6 months after their surgeries. Lower extremity anterior reaching distances were recorded using a Y-balance apparatus. 3 practice trials per leg were performed prior to recording 3 official trials. The greatest reaching distance was used and normalized to leg length for analysis. 1 practice and 3 successful CMVJ trials were also performed using 2 force platforms. Participants stood shoulder-width apart with each foot on a force platform. They were instructed to lower the body and jump vertically as high as possible with an arm swing. Peak forces for each leg during jumping and landing phases were extracted and normalized to body weight. Bilateral asymmetry index was calculated as: (non-injured side − injured side)/(larger value of the 2 sides). For the reaching test, dependent variables were compared among the 3 time points (pre-injury, 3-month post-surgery, and 6-month post-surgery) using a RM·ANOVA, followed by paired t-tests (a = 0.05). For the CMVJ test, dependent variables were compared between pre-injury and 6-month post-surgery using paired t-tests. Results: Participants demonstrated decreased reaching distances for the injured leg and increased reaching distance asymmetries at 3-month and 6-month post-surgery compared pre-injury (p < 0.02). Participants also increased jumping and landing force asymmetries at 3-months and 6-months post-surgery compared to pre-injury (p < 0.03). Conclusion: The results show ACL injuries increase balance and CMVJ asymmetries. Increased asymmetries were likely attributed to decreased performance in the injured leg since participants showed limited asymmetry during baseline testing. Practical Applications: The decreased performance of the injured leg and compensatory loading in the non-injured leg might contribute to high ACL re-injury rates to both legs. Baseline assessments prior to potential ACL injuries should be considered for establishing an individual's pre-injury data. Normalized asymmetries of <10% should be encouraged in post-surgery rehabilitation.

Friday, July 12, 2019, 10:30 am–12:00 pm

Double Peak Muscle Activation Pattern in a Baseball Swing

G. Ball, N. Cardinale, P. Gonzalez, B. Alumbaugh, M. Reeder, and K. Heumann

Colorado Mesa University

The double peak muscle activation pattern has shown a positive relationship with enhanced speed and force in a golf swing and in mixed martial arts striking. Similar to golf and a mixed martial arts strike, a baseball swing is a rotational swinging motion with potential to display the double peak phenomenon. Purpose: To observe muscle activation patterns using surface electromyography (sEMG) in 3 phases of the baseball swing. Methods: Single subject analysis of muscle activation while hitting a ball off of a tee was performed on 6 NCAA Division II male baseball athletes. Subjects were asked to hit a baseball off of a baseball tee into a net using game-emulated swings. Surface EMG electrodes were attached to the left and right rectus abdominis and left and right erector spinae muscles of each subject. While using a high-speed camera synchronized to the Noraxon sEMG electrodes, muscle voltage was recorded and compared to the 3 different phases of the swing: initial movement towards the ball, early to mid-swing phase, and bat to ball contact. Results: Double peak muscle activation patterns were observed in the swings of all subjects; however, the prevalence of the double peak phenomenon varied between subjects. In the swings that produced a double peak, there was a period of initial muscle activation in phase one (initial movement towards the ball), a decrease in muscle activation in phase 2 (early to mid-swing phase), and another spike in muscle activation in phase 3 (bat to ball contact). In the swings where a distinct double peak was not observed, there was a consistent increase in muscle amplitude through phase 3 (bat to ball contact). Conclusion: This study observed a double peak muscle activation pattern during a baseball swing in Division II collegiate baseball players. Practical Applications: These results could be used to enhance training regimens for specific rotational sports that aim to increase the consistency of the double peak in key muscle groups, increasing the effective mass transferred into an object. Future research should be conducted to determine the relationship between double peak muscle activation, bat velocity, and hitting performance.

Friday, July 12, 2019, 10:30 am–12:00 pm

Gender Comparisons of Rate of Neuromuscular Fatigue Across Handle Types During Seated Row Exercise

T. Mack,1 S. Mookerjee,2 S. Meske,2 K. Beyer,2 and D. Drury3

1Bloomsburg University of Pennsylvania; 2Bloomsburg University; and 3Gettysburg College

Muscular responses, rate of neuromuscular fatigue, and performance during seated row exercise may be affected by using a neutral wrist (NW) or a flexed wrist (FW) handle design. Purpose: To compare rate of fatigue differences between the Biceps Brachii (BB), Latissimus Dorsi (LD), and Flexor Carpi Radialis (FCR) across the 2 handle types during seated row exercise. A secondary purpose was to compare performance differences and rate of fatigue between genders. Methods: A sample of 10 males (21.6 ± 1.30 years) and 10 females (22.1 ± 2.80 years) with prior resistance training experience (5.0 ± 2.5 years) completed a 1 repetition maximum (1-RM) seated row with both NW and FW handle types in a randomized order. This was followed by a maximal repetition set to failure using 85% 1-RM with both handle types in a randomized order. Electromyography of the BB, LD, and FCR were assessed during the maximal repetition set to failure at 85% 1-RM. Root mean square from the BB, LD, and FCR were determined for each repetition and slope coefficients were calculated for each maximal repetition set to determine rate of neuromuscular fatigue. Two-way mixed factorial ANOVAs were used to analyze gender and handle differences in 1-RM and number of repetitions to failure. Three-way mixed factorial ANOVA was used to analyze rate of fatigue between gender, muscle, and handle type. Results: The 1-RM lifts were significantly greater (p < 0.001) with the FW handle (90.2 ± 30.5 kg) versus the NW handle (87.8 ± 30.4 kg). There were significant differences (p < 0.001) between genders for the 1-RM lifts across both handle types (males - FW: 117.3 ± 16.5 kg, NW: 114.5 ± 17.2 kg; females—FW: 63.2 ± 6.17 kg, NW: 61.1 ± 6.05 kg). A significant handle×gender interaction (p = 0.047) was noted for repetitions to failure at 85% 1-RM. Post hoc tests revealed that males completed the same number of repetitions with the NW (11.9 ± 3.7 reps) and FW (11.2 ± 2.4 reps) handles, while there was a trend (p = 0.051) for females to complete more repetitions with the FW (12.7 ± 3.7 reps) than NW (11.5 ± 2.3 reps). There was no significant 3-way interaction (p = 0.576) for the rate of fatigue. However, a trend (p = 0.052) for a muscle × gender interaction was noted, and a significant main effect of muscle (p = 0.014) was observed. Regardless of handle or gender, the LD (2.43 ± 1.12 mV/rep) had a significantly (p = 0.014) greater rate of fatigue than the BB (1.22 ± 1.24 mV/rep) or FCR (0.41 ± 2.19 mV/rep). Conclusion: These findings showed significantly higher 1-RM with the FW handle type. Furthermore, females may be able to complete a greater number of repetitions to failure with the FW handle when compared to NW. Finally, neuromuscular fatigue was not affected by gender or handle types, but the LD had the greatest neuromuscular fatigue during the seated row. Possible mechanisms for the 1-RM differences may be related to actin and myosin overlap of the forearm flexors, ergonomic factors such as grip comfort and differences in handle contact surface area. Practical Applications: Alterations in wrist positioning during seated row exercise was shown to result in significant increases in 1-RM for both genders and in repetitions to failure for females only. These findings are important from an equipment design, training, and performance perspective. Using the WF handle allows for a greater amount of weight to be lifted, and may ultimately improve overall development of strength.

Friday, July 12, 2019, 10:30 am–12:00 pm

Effect of Post Activation Potentiation on Weightlifting Performance

S. Chavda,1 A. Sorensen,1 J. Vernau,2 C. Bishop,1 and A. Turner1

1Middlesex University; and 2Highgate school

Introduction: Post activation potentiation (PAP) has been shown to increase kinetic profiles of athletic movements following ballistic or high intensity resistance exercises. The elicitation of PAP is heavily dependent on the biomechanical similarity of the conditioning stimuli to the movement which is to be potentiated. While PAP has been heavily investigated within the context of sprinting and jumping, a lack of information currently exists on the effects of PAP on the kinetics and kinematics of the clean. Purpose: The primary aim of this study was to examine the acute performance enhancing effects of a single supramaximal clean pull performed at 120% of clean and jerk (CJ) one repetition maximum (1RM) on clean performance at 90% 1RM. Methods: Eight (n = 8) ranked collegiate level male and female weightlifters (Mean ± SD; Age: 25.8 ± 6.1 years; Height: 1.69 ± 0.97 m; Mass: 68.1 ± 10.9 kg) volunteered to participate in this study. A control session was used to identify a baseline measure of clean performance conducted at 90% of predetermined 1RM CJ. The experimental condition required participants to perform a single clean pull at 120% of CJ 1RM followed by 3 minutes recovery, prior to executing 3 cleans with one-minute recovery between repetitions. All lifts were performed on a dual force plate set up (Kistler 9286AA and BA, Winterhur, Switzerland), synchronised with a 3D motion capture system (CODA motion capture, Charnwood dynamics, Rothley, UK) to simultaneously record barbell and vertical ground reaction force (vGRF) data. All statistical analyses were performed utilizing SPSS 24.0 (IBM Corp, Armonk, NY). Reliability was quantified for 6 independent kinetic and kinematic variables using the coefficient of variation (CV) and interclass correlation coefficient (ICC). A paired samples t-test was performed to evaluate the differences that may exist between independent variables between the 2 conditions (Control vs PAP). The criterion for statistical significance was set at an alpha-level of p ≤ 0.05. The magnitude of change was also quantified between independent variables using Cohen's d effect sizes, with 95% confidence intervals (CI). Individual subject analysis was calculated using percentage change of the average result from the 3 trials performed at 90% for each condition (control vs experimental). Results: All variables demonstrated good reliability except for the unweighting vertical impulse which showed poor reliability (CV = −22.45, ICC = 0.67 [−0.26 to 0.95]). The paired samples t-test indicated no statistical significance between the control and PAP condition across variables. Magnitude of change between the control and PAP condition were trivial to moderate (ES = 0.14 to −0.67 [−1.27 to 1.12]), displaying both positive and negative effects. Further analysis on individual percentage change within the 6 kinetic and kinematic variables demonstrated values, both positive and negative, ranging from −13 to 27%. Conclusion: The results demonstrate that PAP on kinetic and kinematic measures, during the clean are subject specific, and therefore may negatively affect some and not others. This is evidenced through the lack of statistical significance found between the control and experimental condition across all variables (p = 0.14–0.80) but is highlighted when percentage change is considered for each individual. Practical Applications: The results indicate that utilising a supramaximal clean pull of 120% 3 minutes prior to performing a clean at 90% of 1RM will likely elicit a positive response for some and not others. Given that the current protocol had little effect on the group, it is suggested that individual analysis of PAP on kinetic and kinematic indices related to weightlifting is conducted in response to load, time and rest period. Identifying a potentiating stimulus for an individual within weightlifting may increase the likelihood of greater accessibility of force, thus increasing the chances of lifting a greater load.

Friday, July 12, 2019, 10:30 am–12:00 pm

Lower Limb Strength as an Indicator of Anaerobic and Aerobic Performance

H. Bernard, R. Pettitt, A. Aguinaldo, and J. Dexheimer

Azusa Pacific University

Introduction: The critical speed (CS) model provides estimates of both aerobic and anaerobic fitness components. CS is a theoretically wholly oxidative state whereas D′, the finite capacity for running speeds above CS, utilizes stored energy sources within the active muscle groups like phosphocreatine. Strength training has been shown to improve both aerobic and anaerobic performance. However, few studies have examined the relationship between lower body strength on critical speed (CS) and D′ as determined from a 3-minute all-out test (3 MT). Purpose: The purpose of this study was to examine the relationship of lower body strength to aerobic and anaerobic physiological performance measures in functionally trained athletes. Methods: Nineteen functionally trained athletes, 13 males and 6 females, (Age: 27.8 ± 4.6 years; Height: 70.1 ± 7.3 inches; Mass: 78.3 ± 10.4 kg; Body Fat %: 15.8 ± 5.5%; Experience: 44 ± 32.7 months) completed a graded exercise test (GXT) to determine aerobic power (Vo2max), a 3 MT, Wingate Anaerobic Test (WAnT), and lower body strength assessment. A customized individual GXT run on a treadmill followed by a square wave supramaximal verification phase at 105% peak speed determined each participant's Vo2max. The 3 MT test was performed on a flat track with GPS tracking the participant's distance and time. CS was derived using the average velocity of the last 30 seconds. D′ was calculated using the equation D’ = t (S150s-CS). A 30 seconds WAnT assessed the participant's anaerobic peak (PP) and mean power (MP). Participants performed a 1-repetition maximum (1RM) back squat (BS) and deadlift (DL) to assess total lower body strength (TLBS). The data are reported as means and standard deviations. A Pearson's r correlation was used to determine the relationship between TLBS, BS, and DL and physiological performance. A step wise regression analysis was used on each dependent variable determined to be significant to create a predictive model of performance. The significance level was set a priori at 0.05. Results: Significant correlations were demonstrated between lower body strength measures (mean ± SD: BS = 132.5 ± 31.2 kg; DL = 157.4 ± 33.9 kg; TLBS = 289.9 ± 62.7 kg) and measures of aerobic and anaerobic performance (Vo2max = 47.9 ± 6.4 ml/kg/min; PP = 752.7 ± 159.4 W; MP = 560.6 ± 130.9 W; CS = 3.47 ± 0.54 m/s) (r = 0.492–0.819; p < 0.05). Lower body strength measures were not significantly correlated to D’ (219.9 ± 56.6 m). The results of the regression analysis indicated total lower body strength explained 31% of the variance for Vo2max (F(1,17) = 7.81, β = 0.56, p = 0.012), 67% of the variance for peak power (F(1.17) = 34.7, β = 0.82, p < 0.001), and 58% of the variance for mean power (F(1.17) = 23.64, β = 0.76, p < 0.001). The regression analysis indicated back squat accounted for 24% of the variance for CS (F(1.17) = 5.44, β = 0.492, p = 0.032). Conclusion: Lower body strength significantly predicted anaerobic peak and mean power as well as CS and Vo2max in functionally trained males and females. Practical Applications: TLBS explained a high percentage of the variance for peak and mean power. Therefore, sports requiring high power output in short bursts should focus on improving both BS and DL strength. Given the contribution of TLBS and BS to Vo2max and CS, emphasis should be placed on basic strength training among endurance athletes to enhance performance.

Friday, July 12, 2019, 10:30 am–12:00 pm

Examination of Rate of Torque Development, Rate of Activation, and Muscle Size in Young and Older Men

M. Ferrell,1 M. Magrini,2 R. Colquhoun,3 S. Fleming,1 N. Jenkins,1 and J. DeFreitas4

1Oklahoma State University; 2Creighton University; 3University of South Alabama; and 4OKlahoma State University

Maintaining rapid torque production through the aging process can help sustain independence and functional ability in older adults. Previous research has suggested that muscle size and muscle activation may be important determinants of rapid torque production. Purpose: To examine the influence of age and the relationships among the rate of muscle activation and muscle size (mCSA) of the vastus lateralis (VL) on early phase rapid knee extension torque production Methods: Nineteen young (YA; 22 ± 3 years) and 15 older (OA; 73 ± 6 years) adults completed 2 rapid maximal voluntary isometric contractions (rMVIC). Participants were instructed to kick out as hard and fast as possible for each rMVIC. The rate of torque development was calculated as the average slope achieved during the first 50 ms (RTD0-50) of the 2 rMVICs. Surface electromyographic signals were recorded from the VL during each rMVIC. The rate of muscle activation (RER) was calculated as the slope during the first 50 ms of muscle excitation (nRER0-50) and was normalized to the peak-to-peak M-wave amplitude (%MPP/s). The mCSA of the VL was examined via ultrasound. Separate independent samples t-tests were used to analyze the differences between YA and OA. Additionally, Pearson correlation coefficients were used to analyze the relationships among nRER0-50, mCSA, and RTD0-50. Results: There were significant age differences in mCSA (YA: 31.93 ± 8.16 cm2, OA: 18.02 ± 2.73 cm2, p ≤ 0.001) and RTD0-50 (YA: 922.13 ± 337.32 Nm/s, OA: 576.75 ± 256.15 Nm/s, p = 0.002). However, there was no difference in nRER0-50 (p = 0.12) between YA and OA. When collapsed across age, RTD0-50 was significantly related to nRER0-50 (r = 0.52; p = 0.002) and VL mCSA (r = 0.49; p = 0.003). In the OA, only nRER0-50 was significantly related (r = 0.68; p = 0.005) to RTD0-50 (Figure 1). Interestingly, nRER0-50 was also significantly related with mCSA (r = 0.53; p = 0.041) in the OA. There were no significant relationships between RTD0-50 and mCSA (r = 0.18; p = 0.44) or nRER0-50 (r = 0.31; p = 0.18) in the YA. Conclusion: There were age related differences in muscle size and RTD0-50, but not nRER0-50. The significant relationship between nRER0-50 and RTD0-50 suggests that neural factors are important for early torque production in the OA. Further, the significant positive relationship between nRER0-50 and VL mCSA in the older adults suggest that older adults who have greater muscle size, may also have a greater ability to rapidly activate their muscles. Practical Applications: Strength and conditioning professionals should prioritize exercise that enhances or maintains muscle size and that requires rapid activation to help reduce the age-related decline in rapid torque production and improve functional ability in older adults.

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Figure 1.:
Relationships between RTD 0–50 and nRER 0–50 in younger and older men. RTD 0–50 = Rate of torque development in the first 50 ms, nRER 0–50 = Normalized rate of muscle activation in the first 50 ms. *Significant relationship between RTD 0–50 and nRER 0–50 in older men (p ≤ 0.05).

Friday, July 12, 2019, 10:30 am–12:00 pm

Patterns of Neuromuscular Responses During Fatiguing, Maximal Bilateral Leg Extensions

J. Anders,1 C. Smith, J. Keller,2 E. Hill,3 T. Housh, R. Schmidt, and G. Johnson4

1University of Nebraska- Lincoln; 2University of Nebraska-Lincoln; 3University of Nebraska Lincoln; and 4University of Nebraska-Lincoln

Purpose: The purpose of the present study was to determine the patterns of neuromuscular responses from both vastus lateralis (VL) muscles during fatiguing, bilateral, maximal, isokinetic leg extensions. Methods: Twelve men (21.2 ± 2.4 years) performed consecutive, maximal, bilateral, concentric isokinetic leg extensions at 180°·s−1 until their peak toque was reduced by 70% (93 ± 10 repetitions). The amplitude (root mean square = AMP) and frequency (mean power frequency = MPF) contents of the electromyographic (EMG) and mechanomyographic (MMG) signals from the VL muscles of both thighs were recorded simultaneously during each repetition of the fatiguing bout. EMG AMP, EMG MPF, MMG AMP, and MMG MPF were normalized to their initial 10% values from the fatiguing task. Four, 2 (right and left VL) × 19 (10–100% of the total repetitions in 5% increments) repeated measures ANOVAs were used to determine mean differences for each normalized neuromuscular parameter. Polynomial regression analyses were utilized to characterize the patterns of neuromuscular responses. Results: The results demonstrated no significant VL × repetitions interactions for EMG AMP, EMG MPF, or MMG AMP. There was a significant interaction for MMG MPF (p < 0.045; = 0.174), but no significant change over repetitions for either VL muscle. EMG MPF and MMG AMP demonstrated significant (p < 0.001; η = 0.464 and p < 0.001; = 0.341, respectively) main effects for repetitions only. Polynomial regression analyses for the averages of both VL muscles exhibited negative, quadratic relationships for EMG AMP versus repetitions (R = 0.854) and EMG MPF (R = 0.956) versus repetitions and a negative, linear relationship for MMG AMP versus repetitions (R = 0.964). There was no significant (p > 0.05) relationship for MMG MPF versus repetitions. Conclusion: The results of the present study demonstrated no differences between the right and left VL muscles for their patterns of neuromuscular responses during the fatiguing bilateral leg extensions. The decreases in EMG MPF and MMG AMP, but a lack of changes in EMG AMP and MMG MPF suggested the reduced force production during bilateral leg extensions was likely due to peripheral fatigue, and not changes in central drive to the muscle. Practical Applications: The findings of this study suggest fatigue elicited by repeated bilateral muscle actions are the result of peripheral mechanisms such as the build-up of metabolic byproducts. Strength and conditioning professionals should consider utilizing metabolic training modalities, such as HIIT training, to mitigate the onset of fatigue.

Friday, July 12, 2019, 10:30 am–12:00 pm

Impact of Competitive Season Stress on Indices of Motor Control in D1 Softball Players

K. Nottingham,1 M. DiBiasio,1 N. Wagner,1 T. Purdom,2 and K. Levers

1The George Washington University; and 2Longwood University

Previous research has demonstrated significant negative correlations between physiological stress and neuromuscular control in highly trained athletes. However, the relationship between full body motor control and physiological stress in softball athletes is unclear. Purpose: The aim of this study was to observe the effects of competitive season training stress on motor control in Division I softball players. Methods: Thirteen Division I female softball players (Mean ± SD: 19.9 ± 1.3 years, 70.5 ± 6.8 kg, 167.4 ± 6.1 cm, 26.4 ± 5.5%BF) completed physiological stress and motor control performance testing across the competitive season, specifically pre-season (PRE), mid-season (MID) and post-season (POST). Upper and lower body neuromuscular control were measured using the Functional Movement Systems Motor Control Screen (MCS). Upper body MCS measured unilateral horizontal reach (URR, ULR) in a three-point high plank position via the reaching non-stance arm. The lower body MCS measured unilateral anterior reach (LRR, LLR) in single leg stance via the reaching non-stance foot. MCS passing criteria are: (1) unilateral reach greater than double foot-length (DBL) and (2) <4 cm left-right discrepancy (LRD). Participants arrived fasted (>4 hours), caffeine-free (>12 hours), and exercise and alcohol-restricted (>24 hours) with salivary cortisol (sCORT) sampling times standardized to control for diurnal variability. Statistical analysis included normalized reach scores for both left and right limbs in proportion to DBL [(nURR, nULR, nLRR, nLLR)/DBL)*100]. Two separate 3 × 3 repeated measures ANOVAs were used to assess upper and lower motor control, respectively, over the competitive season. A one-way repeated measures ANOVA was used to monitor sCORT across the competitive season. Post hoc analyses using the LSD test were used to evaluate pairwise comparisons when significant interactions were observed. Results: A significant sCORT main time effect was observed (F1,12 = 3.64, p = 0.042, = 0.37). Pairwise comparisons revealed a 43.5% sCORT increase PRE to POST (Mean ± SD: PRE: 0.09 ± 0.05 ug/dL, POST: 0.16 ± 0.08 ug/dL, p = 0.021) with no significant change PRE to MID or MID to POST (p > 0.05). A significant upper MCS main time effect was observed (F1,12 = 6.54, p = 0.013, = 0.85). Pairwise comparisons demonstrated improvements in nURR and nULR PRE to POST (nURR: PRE: 1.02 ± 0.18, POST: 1.19 ± 0.15, p = 0.002; nULR: PRE: 1.08 ± 0.18, POST: 1.22 ± 0.13, p = 0.003), and MID to POST (nURR: MID: 1.08 ± 0.12, p = 0.001; nULR: MID: 1.08 ± 0.16, p = 0.007). Changes in upper MCS and sCORT were not statistically correlated (p > 0.05). Upper LRD and lower MCS (nLRR, nLLR, LRD) were not affected by competitive season training load nor associated with sCORT (p > 0.05). Conclusion: Improved upper MCS performance in a throwing-based sport was expected but not with simultaneously increasing physiological stress. Team competition statistics showed game winning percentage improvement across the season (PRE: 52.9%, MID: 76.5%, POST: 88.2%), further supporting the motor control performance trend. Improved performance during periods of heightened hormonal arousal have been previously described through the Inverted U Hypothesis, which states that optimal performance exists at a moderate level of arousal.1 Compared to similar athletic-based research accounting for diurnal cortisol flux, sCORT values in this population were centralized around the 50th percentile.2,3 Based on these trends, moderate levels of sCORT in softball athletes may elucidate greater motor control and performance. Practical Applications: MCS is a valuable tool for motor control evaluation, however more frequent neurological fatigue and stress hormone testing across the competitive season in this population is likely required to predict performance outcomes.

Friday, July 12, 2019, 10:30 am–12:00 pm

Validity and Reliability of an Inertial Measuring Unit System on Reactive Strength Index Measures

S. Montalvo,1 S. Dorgo, M. Gonzalez,1 and M. Dietze-Hermosa2

1University of Texas at El Paso; and 2The University of Texas at El Paso

Reactive Strength Index (RSI) is an indicator of reactive capacity. Explosive sports that involve jumping require an efficient usage of the energy generate through the stretch-shortening cycle. Several models exist to measure reactive capacity. Traditionally, RSI has been calculated by dividing contact time by jump height. Recently, an Inertial Measuring Unit system (PushBand 2.0) has been introduced as an alternative measure of RSI. The purpose of this study was twofold: 1) to assess the relationship between RSI data obtained through the Pushband 2.0 and the gold standard force plate RSI scores, and 2) to determine the intra-subject reliability and stability of the instruments. Methods: Twenty subjects (10 males and 10 females; mean & SD; Age 23.5 ± 1.88 years, Height 1.60 ± 0.034 m, Weight 69.93 ± 18.76 kg) attended a single-session vertical jump assessment. Subjects first performed a general warm-up followed by a series of dynamic movements that resemble the vertical jump. Following this, subjects were instructed on proper jumping technique involving a 90-degree (knee flexion) squat to account for inter-subject variability. Lastly, subjects performed 2–3 jumps on the force plates for familiarization purposes. Thereafter, subjects performed 5 repetitions of a Depth Jump using a 0.3 m box. Subjects were verbally encouraged to jump as high as possible and instructed to land with their legs as straight as possible. A total of 100 jumps were used for the final analysis. Force plate data was obtained with 2 Amti force plates at a 1,000 Hz. RSI was calculated as contact time/flight time. Data from the PushBand was obtained at a sampling rate of 1,000 Hz and analyzed using contact time/flight time method. Data was collected and exported to Excel then to SPSS IBM 23 for statistical analysis. Reliability of the devices and absolute agreement was measured using an intra-class correlation (ICC) with 95% Confidence Intervals (95% CI). Analyzes by sex were also included. Results: The correlation between devices was low (ICC = 0.288, 95% CI = 0.82 and 0.10, p > 0.05). The intra-subject RSI analysis for the force plate (1.06 ± 0.42 RSI) and PushBand 2.0 (1.34 ± 0.53 RSI) were high (ICC = 0.965, 95% CI = 0.93 and 0.98, and ICC = 0.926, 95% CI = 0.85 and 0.96, respectively) (p < 0.05). Male RSI data for the Force Plate (1.05 ± 0.48 RSI) and PushBand (1.48 ± 0.45 RSI) also showed a poor agreement (ICC = 0.04, 95% CI = −0.51 and −0.34, p > 0.05). Similarly, agreement for female data between the Force Plate (1.08 ± 0.35 RSI) and PushBand 2.0 (1.19 ± 0.57 RSI) was moderate (ICC = 0.66, 95% CI = −1.49 and 0.57, p > 0.05). Conclusion: There was a discrepancy between the depth jump movement RSI scores for the force plates and PushBand 2.0. It appears that the PushBand overestimates RSI scores. Both instruments resulted in high intra-subject reliability. Practical Applications: The PushBand might be a reliable instrument, however, coaches might want to be aware of the overestimation on RSI scores when compared to the force plates.

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Figure 1.:
Correlation between force Plate and Push Band 2.0 RSI data.

Friday, July 12, 2019, 10:30 am–12:00 pm

Comparison of Posterior Chain Muscles Activation During the Hyperextension and Reverse-Hyperextension

M. Cuthbert, J. McMahon, N. Ripley, and P. Comfort

University of Salford

Force development and absorption is important during athletic tasks. The posterior chain musculature, particularly the hip extensors (gluteus maximus [GMax] and hamstrings), play an important role in enhancing performance and reducing the risk of injury during those tasks. Identifying exercises that sufficiently activate these muscle groups, via electromyography (EMG), is important to inform appropriate programming and prescription of exercises. The hyperextension (HYP) and reverse-hyperextension (RHE) both involve extension of the hip, albeit with the movement pattern reversed between exercises: the HYP involves raising the torso while the legs are stationary, whereas the legs are raised while the torso is stationary during the RHE. The resulting difference in activation of the hip extensors is unknown. Purpose: To compare the level of muscle activation produced in 3 posterior chain muscles including erector spinae (ES), GMax and biceps femoris (BF) during the concentric and eccentric phases of the HYP and RHE. Methods: Subjects (n = 10; age = 23 ± 4 years, height = 175.9 ± 6.9 cm; mass = 75.2 ± 9.7 kg) had EMG electrodes placed on the ES, GMax and BF muscles in accordance with SENIAM guidelines. Subjects performed 3 maximum voluntary contraction trials of lumbar extension and hip extension using an isokinetic dynamometer, in order to normalize the EMG during the HYP and RHE. Three repetitions of each exercise were executed with a load applied for the RHE equated to participants' upper bodyweight during the HYP. ES activation was normalized to back extension, and both GMax and BF activation were normalized to the peak EMG achieved during prone hip extension. EMG data were analyzed in a bespoke Excel spreadsheet, identifying the 2 phases based on thresholds of >2 standard deviations +mean EMG acquired during periods of residual EMG for the start and end points of the exercise, the end of the concentric and start of the eccentric phases were identified using a virtual marker. Data were compared between HYP and RHE using paired samples T-tests, or Wilcoxon's tests for variables that failed to meet parametric assumptions. Hedges geffect sizes were also calculated to determine the magnitude of differences between the exercises. An a priorialpha level was set at p < 0.05. Results: High reliability (intraclass correlation coefficients ≥0.925) was observed with low variability (coefficient of variation ≤11%). During the concentric and eccentric phases, RHE exhibited moderate to large (g ≥ 1.00) and significantly greater (p ≤ 0.002) EMG compared to the HYP in all 3 muscles (Table 1). Conclusion: The RHE results in greater muscle activation compared to the HYP during all phases, particularly for the GMax where activation, during the HYP, was low (≤15%) (Table 1). Practical Applications: When prescribing posterior chain-based exercises, the RHE appears to be superior to the HYP in activating the GMax, BF and ES, thus practitioners should consider including the RHE to primarily train the hip extensors.

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Mean, Standard Deviation, Reliability and Statistical Comparison of the Hyperextension and Reverse-Hyperextension.

Friday, July 12, 2019, 10:30 am–12:00 pm

Ground Reaction Force and Electromyographic Determinants of the Jab in Boxers

S. Lenetsky,1 M. Brughelli,1 R. Nates,1 J. Neville,1 M. Cross,2 A. Lorimer,3 and K. Heumann4

1Auckland University of Technology; 2Univ Savoie Mont Blanc; 3Bond University; and 4Colorado Mesa University

Introduction: Effective mass (EM), an athlete's inertial contribution to a strike, has been identified as a key impact kinetic in punching. While double peak muscle activation (DPMA) has been theorised as vital to the development of EM, no studies have empirically identified its determinants. Purpose: To investigate the relationship between ground reaction forces (GRF) and electromyographic (EMG) to EM in the jab of a cohort of experienced boxers. Methods: Ten experienced and competitive male boxers (age = 25.6 years ± 5.97, height = 179.5 cm ± 7.72, mass = 95.66 kg ± 21.82, and years training = 10.3 years ± 5.97) participated in this study. The following muscles were prepared for EMG data collection: triceps brachii (LTB and RTB), latissimus dorsi (LLD and RLD), rectus abdominis (LRA and RRA), and rectus femoris (LRF and RRF) of the lead and rear sides. After preparation, participants performed a standardised warm-up, maximal voluntary isometric contractions for EMG normalization, and familiarisation. Five maximal punches against an instrumented bag were used for analysis. Trials were recorded with an EMG system, 2 force plates (1 plate under each leg), 2D high speed video (HSV), and an instrumented bag to measure impact kinetics; all devices sampled at 1,000 Hz, were time synchronised to impact. 2D HSV was used to determine pre-impact punch velocity of the jabs which was used to calculate EM with impulse measured through the instrumented bag. A hierarchical regression using magnitude-based inference was employed to identify the determinants of EM. Pearson correlation coefficient (r) and co-efficient of determination () were calculated for each model. Inferences based on the square-root of the were used to describe the magnitude of the observed relationship. A 5:1 ratio of boxers to independent variables (10 boxers = maximum of 2 independent variables) was used to account for shrinkage and inflated error rates due to the study's relatively small sample size. Results: EM was determined by the GRF variables of minimal lead leg X axis value during the impact phase (force applied towards the boxer's mid-line) and max GRF development in the lead leg (Y axis) during the execution phase. Both variables had negative relationships with EM. RTB results were the final EMG determinants of EM in the jab. RTB duration of activation had a negative relationship (r = −0.51) and the phase of activation start had a positive relationship (r = 0.41) with EM. The key determinants of EM in the jab were minimal lead leg GRF (X axis) and the duration of activation of the RTB. Conclusion: These findings contrast with the theory of optimizing EM. Instead of DPMA being a primary determinant of EM, 2 variables which optimize the rotation of the torso were key to the development of EM in the jab. Practical Applications: These results indicate that to improve EM in the jab of boxers, practitioners should focus on improving rotational performance over methods thought to improve DPMA.

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Table 1.:
Determinates of effective mass in the jab punch.

Friday, July 12, 2019, 10:30 am–12:00 pm

The Effects of Velocity and Muscle Size on Knee Extension Mean Power in Younger and Older Men

M. Magrini,1 R. Colquhoun,2 M. Ferrell,3 S. Fleming,3 N. Jenkins,3 and J. DeFreitas4

1Creighton University; 2University of South Alabama; 3Oklahoma State University; and