2020 NSCA Research Abstracts : The Journal of Strength & Conditioning Research

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Abstracts

2020 NSCA Research Abstracts

Journal of Strength and Conditioning Research: April 2021 - Volume 35 - Issue 4 - p e3-e288
doi: 10.1519/JSC.0000000000003877
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(01) Validity of Smartphone Heart Rate Variability before and Post-Resistance exercise

C. Holmes,1 G. Brisola,2 S. Wind,3 H. MacDonald,3 M. Fedewa,4 L. Winchester,4 and M. Esco3

1Washing University School of Medicine;2Sao Paulo State University;3University of Alabama; and4The University of Alabama

Recent technological innovations in Bluetooth finger pulse sensors and various heart rate straps have allowed for the convenient acquisition of heart rate variability (HRV) for tracking autonomic function among athletes outside of laboratory settings. However, few studies have investigated both the agreement and reliability of using smartphone photoplethysmography (PPG) recordings against electrocardiogram (ECG) at rest and following sympathetic activation from resistance exercise. Purpose: The aim was to examine the validity of HRV measures from PPG via smartphone application under resting and post-resistance exercise conditions. The secondary aim was to examine the intraday and interday reliability of smartphone PPG. Methods: Thirty-one resistance-trained individuals (29% female, 23.9 ± 5.4 years, 75.9 ± 12.9 kg, 17.6 ± 7.2% fat) participated in this study. After a familiarization session, subjects completed 2 simultaneous ultrashort-term ECG and PPG (BasePre1 and BasePre2) measurements followed by 1-repetition maximum (1RM) testing for Back Squat, Bench Press, and Bent-over Rows. At least 72-hours later, subjects performed a resistance exercise protocol, with 3 simultaneous ultrashort-term ECG and PPG measurements: 2 pre-exercise (HVPre1 and HVPre2 and one post-exercise (HVPost). The log-transformation of the root mean square of successive RR differences (LnRMSSD) from ECG and PPG were compared with paired samples t-tests, Cohen's d effect sizes (ES) and Pearson product correlations. Agreement between the ultrashort-term LnRMSSD values was evaluated using Bland-Altman analysis. The agreement was qualified as the calculated ratio of half the 95% confidence interval (CI) and the mean of the average values: “good” = <0.1, “moderate” = 0.1–0.2, and “insufficient”= >0.2. Intra-class correlations (ICC) were determined for intraday and interday reliability pre-exercise PPG values. Correlation values between 0 and 0.30 = small, 0.31–0.49 = moderate, 0.50–0.69 = large, 0.70–0.89 = very large, and 0.90–1.00 = near perfect. Results: Paired-samples t-tests showed small-moderate differences for all comparison measurements between ECG and PPG: BasePre1 (p = 0.003), BasePre2 (p = 0.019), HVPre1 (p = 0.036), HVPre2 (p = 0.001), and HVPost (p = <0.001). Correlations between the ECG and PPG LnRMSSD comparison ranged from moderate-very large (BasePre1 = 0.59, BasePre2 = 0.63, HVPre1 = 0.626, HVPre2 = 0.76, and HVPost = 0.41, all p < 0.05). The quality of the agreement for all pre-exercise measures was classified as “good” but the post-exercise agreement was deemed “insufficient”. The PPG LnRMSSD exhibited nearly-perfect intraday reliability (ICC = 0.91) and very large interday reliability (ICC = 0.88). Conclusions: Though significant differences were detected between ECG and PPG, the smartphone-derived LnRMSSD displayed large correlations, good agreement, and strong reliability under-resting conditions. However, greater differences, weaker correlations and insufficient agreement were seen for post-exercise measures. Smartphone PPG seems to be an appropriate surrogate for ECG to obtain valid HRV data at rest but deteriorates following resistance exercise. Practical Applications: Ultrashort-term, smartphone PPG measures of HRV allow for daily monitoring to provide more insight into how athletes are responding to training. However, increased sympathetic activation can decrease the accuracy of PPG. Precautions should be taken to limit external stressors to derive valid measures of HRV.

(2) Effects of a 9-Month Neuromuscular Training Program on Isometric & Dynamic Force-Time Characteristics & Vaulting Take-off Velocity in Young Gymnasts

S. Moeskops,1 P. Read,2 G. Haff,3 J. Oliver,1 G. Myer,4 J. Cronin,5 and R. Lloyd1

1Cardiff Metropolitan University;2Aspetar Sports Medicine Hospital;3Center for Exercise and Sports Science Research, Edith Cowan University;4Division of Sports Medicine, Cincinnati Children's Hospital; and5AUT University

Previous research exploring the effectiveness of neuromuscular training (NMT) programs in young female gymnasts [1,2] have primarily implemented short-term interventions and failed to examine the training benefits on gymnastics performance. Purpose: To examine the effects of a 9-month NMT intervention on isometric and dynamic force-time characteristics during strength and power tests and vertical take-off velocity during gymnastics vaulting. Methods: Forty-three pre–pubertal female gymnasts were sub-divided into gymnastics + NMT (GYM + NMT; n = 16), gymnastics only (GYM, n = 15) groups and a maturity-matched control (CON; n = 12). Biological maturation was estimated using percentage of predicted adult height (%PAH) [3]. The GYM + NMT group followed a 9-month NMT program, consisting of 2 × 1-hr sessions/week, while the GYM and CON groups did not receive the additional training stimulus. Force-time characteristics during the isometric mid-thigh pull (IMTP), countermovement jump (CMJ), and drop jump (DJ) tests were measured at baseline (T1) and thereafter on a 3-monthly basis (T2, T3 and T4). Vertical take-off velocity during a straight jump vault was calculated using 2D video analysis. A 3 × 4 (group × time) repeated measures ANOVA with a Bonferroni post-hoc analysis was used to identify any significant between-group differences (p < 0.05), and Hedges' g to calculate effect sizes [4]. Results: Data indicated moderate significant increases in IMTP absolute peak force (PFabs) from baseline to each subsequent testing session and relative peak force (T1-T3 and T1-T4) in the GYM + NMT, and a small significant increase in PFabs from T1-T4 in the GYM group (Table 1). CMJ data showed jump height (JH) and braking impulse (Impulsebrake) significantly increased from T1-T3 in the GYM + NMT group, while propulsive impulse (Impulseprop) significantly increased from baseline to each subsequent testing session. Impulseprop was the only measure that significantly increased in the GYM group (T1-T4). DJ data revealed significant improvements in JH and reactive strength index (RSI) from T1-T3 and T1-T4 in the GYM + NMT, with no significant changes in the GYM group. Significant increases in vaulting vertical take-off velocity were only identified in the GYM + NMT (T1-T4). CON group showed no significant changes, other than a significant increase in DJ contact time (T1-T4). Conclusions: The additional NMT stimulus significantly improved vaulting vertical take-off velocity, maximal isometric force producing capabilities, and slow and fast-stretch shortening cycle function in the GYM + NMT cohort; however, these changes were not evident for GYM or CON. Practical Applications: Positive changes in isometric and dynamic kinetic variables can be achieved in prepubertal female gymnasts following 3 months of NMT and appear to be beyond those obtained from gymnastics alone. Practitioners should realise that the beneficial effects from NMT may take longer to transfer to vaulting performance.

Table 1 - Group analysis of IMTP, CMJ, DJ variables and vaulting vertical take-off velocity.

(3) Lifting Straps During the Deadlift Exercise: Influence on the 1 Repetition Maximum and Load-Velocity Profile

I. Jukic,1 A. García-Ramos,2 D. Omcirk,3 J. Malecek,4 and J. Tufano5

1Sport Performance Research Institute New Zealand (SPRINZ);2University of Granada;3Charles University, Faculty of Physical Education and Sport;4Faculty of Physical Education and Sport, Charles University; and5Charles University

Maximal strength levels as well as load-velocity profiles are often monitored during resistance training, but it is unknown whether the presence of lifting straps affects these measures. Purpose: To compare the one repetition maximum (1RM) and load-velocity (LV) profile between deadlifts performed with (DLw) and without (DLn) lifting straps. Methods: The full individual LV relationship of 18 men (age: 24.3 ± 2.4 years; body height: 180.6 ± 6.9 cm; body mass: 85.8 ± 8.0 kg) was randomly evaluated during 2 separate sessions for the DLw and DLn via an incremental loading test. Results: 1RM was greater (p < 0.001; g = 0.56 [0.32, 0.79]) for DLw (177.0 ± 28.9 kg) compared to DLn (160.6 ± 26.0 kg). A highly linear relationship between mean velocity (MV) and %1RM was observed for both conditions (R2 > 0.95; SEE < 6.18% 1RM for pooled data and R2 > 0.98; SEE < 3.6% 1RM for individual data). However, MV associated with each %1RM was greater for DLn, and these differences were accentuated as the loading magnitude increased (g = 0.30–1.18). 1RM was strongly associated between both conditions (r = 0.875 [0.71, 0.95]) whereas MV at 1RM (r = 0.21 [−0.25, 0.60]) was unrelated between conditions. The slope of the LV profiles (r = 0.845 [0.64, 0.94]) was correlated but differed (g = 0.41 [0.16, 0.66]) between DLw and DLn while the mean test velocity of all loads was unrelated (r = 0.270 [−0.20, 0.64]). Conclusions: The use of lifting straps during deadlifts allowed for a higher 1RM. Although LV relationships were highly linear for both DLw and DLn, these relationships markedly differed since the velocity attained at each %1RM was considerably faster during DLn, likely as a result of lighter absolute loads during DLn (Figure 1). This, together with lack of associations in MV at 1RM and the mean test velocity between DLw and DLn, highlight that the LV profiles of the deadlift exercise are subject-dependent and heavily influenced by the use of lifting straps. Practical Applications: LV profiles of deadlifts performed with and without lifting straps largely differed. Therefore, whether athletes are going to use lifting straps or not during their regular training sessions must be considered before creating their individual LV profiles and using velocity to prescribe their submaximal relative loads. Finally, sport professionals should be aware that individual LV relationships provide more accurate estimations of DLw and DLn %1RM than a general LV relationship. Therefore, individual LV profiles should be created for each athlete in the same condition that are going to be used in training in order to obtain a more precise estimation of the submaximal relative loads.

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Figure 1.:
Load – velocity relationships obtained for the deadlift exercise performed with (black dots and the line) and without (grey dots and the line) lifting straps.

(5) Are There Differences in Velocity Measurements Between Device: Effect on Squat Jump Velocity?

Y. Kotani,1 S. Guppy,2 J. Lake,3 K. Nosaka,4 N. Hori,5 and G. Haff1

1Center for Exercise and Sports Science Research, Edith Cowan University;2School of Medical and Health Sciences, Edith Cowan University;3University of Chichester;4Edith Cowan University; and5Western Australian Institute of Sport High Performance Service Center

Purpose: The purpose of this study was to compare squat jump (SJ) load-velocity (LV) relationships for peak (PV) and mean (MV) velocity recorded with a force plate and 4 commercially available velocity measurement devices. Methods: Fifteen resistance trained subjects (age: 27.2 ± 5.1 years; height: 1.73 ± 0.09 m; body mass [BM]: 75.8 ± 12.5 kg, back squat one-repetition maximum [BSQ1RM]: 144.7 ± 37.7 kg, 1.90 ± 0.33 kg/BM) completed 2 sessions separated by at least 72 hours. Anthropometric data, SJ starting position and self-selected stance width were determined in Session 1, followed by BSQ1RM and SJ protocol familiarization. In Session 2, a series of SJs were performed in a quasi-randomized order against a series of increasing loads (+10%) between 0 and 100% of BM, with one-minute rest between jumps and two-minutes allocated between loads. All SJ PV and MV were simultaneously measured with a GymAware (GYM), Beast sensor (BST), Bar Sensei (BS), and PUSH BandTM 2.0 (PUSH). Data collected with these devices were then compared to velocities calculated from an AMTI force plate (FP) sampling at 2000 Hz. A 5 (device) × 11 (load) repeated measures analysis of variance was used to determine if significant differences were present. When significant effects were found, paired comparisons using Holm's Sequential Bonferroni correction were performed. Results: Significant main effects for intensity (p < 0.001, μ2 = 0.96) and device (p < 0.001, μ2 = 0.86), as well as, intensity × device interactions (p < 0.001, μ2 = 0.42) were determined when examining PV (Table 1). Follow-up tests indicated that PV was significantly different (p < 0.05) between the FP, PUSH, and BST at loads >20% of BM. Additionally, PV was significantly different between the BST, BS and PUSH for all loads >30% of BM (Table 1). There were significant main effects on MV for intensity (p < 0.001, μ2 = 0.92) and device (p < 0.001, μ2 = 0.93), as well as intensity × device interactions (p < 0.001, μ2 = 0.57). After running follow-up tests significant MV differences (p < 0.05) were noted between the FP, BS, and PUSH at all loads >30% of BM. Additionally, MV was significantly different between the GYM, BST, and PUSH for all loads between 20 and 60% of BM (Table 1). Conclusions: The PV and MV from each device were not interchangeable. With loads above 30% of BM there were differences PV and MV values measured by the FP, BS and PUSH devices. Based upon the differences in each device's velocity the measurement device will likely also influence LV profiles. Practical Applications: Strength and conditioning professionals creating a LV profile should note that velocity measurement devices are not interchangeable. Because of the differences between measurement devices it is important that the same device is used to obtain the LV profile and guide velocity-based training.

Table 1 - Peak and mean velocity quantified by a FP and estimated by GYM, BST, BS, and PUSH.
Note: * = Significantly different from FP (p < 0.05), $ = Significantly different from GYM (p < 0.05), # = Significantly different from BST (p < 0.05), ^ = Significantly different from PUSH (p < 0.05).

(6) The Effects of Inter-Set Stretching on Muscular Adaptations in Strength-Trained Males

T. Morrison,1 T. Wadhi,2 C. Barakat,1 A. Anand,2 S. Zazzo,1 A. Murphy,1 J. Pearson,3 Z. Rodriguez,1 J. Sullivan,1 and E. Souza1

1University of Tampa;2The University of Tampa; and3University of Kansas

Introduction: Resistance training (RT) has been shown to increase muscular adaptations. Mechanical tension is considered to be one of the most important stimuli for muscle growth. Therefore, manipulating the time a muscle is under tension would increase mechanical strain optimizing RT-induced adaptations. It has been suggested that stretching between working sets (i.e., inter-set stretching [ISS]), is one way to increase time under tension. In fact, it has been found that ISS combined with RT can induce hypertrophic gains in untrained individuals. Additionally, loaded stretching has demonstrated muscle hypertrophy in untrained individuals. However, there is a lack of research regarding how ISS with a load affects muscular adaptations in trained males. Purpose: To determine the effects of ISS vs. traditional resistance training (TRT) on muscular adaptations in strength-trained males. Methods: Twenty-six strength-trained males were randomized into 2 groups based on the sum of 2 sites of their pectoralis major muscle thickness (∑MT): ISS (n = 12) and TRT (n = 14). Both groups performed 8 weeks of RT that included the flat and incline bench press exercises. A 100 twenty second rest periods were granted to both groups. However, the ISS group held a loaded passive stretch using a cable fly machine for 30 seconds between each working set during their rest period. The loaded stretch for each ISS subject was based on their load for the working sets on each exercise (∼15% of working weight). Both groups performed training sessions twice a week. Muscle thickness (MT) was measured at 2 points on the pectoralis major: the lateral portion (LMT) and at the belly (BMT). Maximum strength was measured through one repetition maximum testing (1RM) on the flat bench press. Rating of perceived exertion (RPE) and total volume load (VL) were tracked for each group as well. Results: There was no difference between groups for average RPE (p = 0.48; ISS (au) = 8.16 ± 0.65; TRT (au) = 8.01 ± 0.42) and VL (p = 0.98; ISS (kg) = 73,387.2 ± 10,092.4; TRT (kg) = 73,253.4 ± 12,697). Both groups increased LMT (p ≤ 0.0001; ∆LMT (cm): ISS = 0.32 ± 0.16; TRT = 0.28 ± 0.17) as well as BMT (p ≤ 0.0001; ∆BMT (cm): ISS = 0.27 ± 0.17; TRT = 0.30 ± 0.22). Additionally, 1RM also increased in both groups from pre to post (p ≤ 0.0001; ∆RM (kg): ISS = 6.61 ± 3.80; TRT = 7.45 ± 5.66). Descriptive statistics, effect sizes, and 95%- confidence intervals are presented in Table 1. CONCLUSION: Inter-set stretching in a RT short-term period neither improves nor decreases muscular adaptations in strength-trained males. Practical Applications: The results of this study may be useful to strength-trained males looking to improve muscular strength and hypertrophy of the chest. It can be stated that these individuals may not see increased benefits by the addition of ISS in their short-term training program lasting 8 weeks.

Table 1 - Summary of the outcomes (mean ± SD).
LMT = lateral muscle thickness; BMT = belly muscle thickness; ∑MT = sum of muscle thickness; 1RM = one repetition maximum; ES = effect sizes; 95%-CI = 95% confidence intervals.

(8) The Effects of Slow vs. Fast Repetition Tempo on Muscle Hypertrophy and Strength in Resistance-Trained Individuals

J. Pearson,1 T. Wadhi,2 C. Barakat,3 D. Aube,4 S. Zazzo,3 J. Sullivan,3 and E. Souza3

1University of Kansas;2The University of Tampa;3University of Tampa; and4High Point University

Introduction: Repetition tempo (RT) has been a training variable debated for years. Current literature suggests there is a minimal significance between performing repetitions at a slower RT compared to faster when the goal is muscular hypertrophy and strength. However, nearly all of the studies on RT were carried out in untrained individuals, thus warranting further investigation in trained populations. For instance, trained individuals may need a greater stimulus to potentiate muscular adaptations. Additionally, to our knowledge, there is no study utilizing a within-subject design to reduce biological variability in resistance-trained individuals. Purpose: The aim of this study was to examine the effects of slow vs. fast RT on lower body muscular strength and hypertrophy in resistance-trained males utilizing a within-subject design. Methods: Thirteen resistance-trained men participated in this study (age: 23.4 years ±5.97, 1RM Squat: BM Ratio 2.06 ± 0.4). Each leg was randomly assigned to either SLOW (1-0-3) or FAST (1-0-1) tempo training based on the sum of anterior thigh muscle thickness (MT). Subjects trained using a leg-extension (LE) machine for 8 weeks at 2 times/week and performed the same absolute intensity, set and repetition range. Three sets of 8–10 RM performed to concentric failure were executed for weeks 1–4, then a fourth set was added for weeks 5–8. Additionally, for the SLOW leg, if the subject was unable to match volume-load (VL), we employed 8-second rest pauses as needed to ensure total VL was equated between legs. The only difference was the total time under tension between legs due to the different RTs. 1-RM and MT assessments were performed on both limbs at 40% (PMT) and 60% (DMT) femur lengths at baseline and post-testing. Results: For the PMT, there was a main time effect (p < 0.0013) indicating both legs responded in a similar fashion (Estimated differences: FAST 0.24 cm, 3.6%; SLOW: 0.20 cm, 3.1%). For the DMT, there was also a main time effect (p < 0.0137) (Estimated differences: FAST 0.28 cm, 5.5%; SLOW: 0.12 cm, 2.2%). However, there was a main group effect (p < 0.0250) indicating that SLOW leg had an overall greater DMT than FAST leg (Estimated:0.18 cm, 2.4%, 95%-CI: 0.02–0.34 cm). For ΣMT, there was a main time effect (p < 0.0030) indicating both legs increased similarly, (Estimated differences: FAST 0.53 cm, 4.4%; SLOW: 0.33 cm, 2.8%). Regarding strength, there was a main time effect (p < 0.0001) for maximum strength indicating both legs increased RM similarly (Estimated differences: FAST 9.07 kg, 17.0%; SLOW: 11.9 kg, 22.1%). Study outcomes listed in Table 1. Conclusions: Our results demonstrated both FAST and SLOW RT improved muscular adaptations in a similar fashion. However, DMT was greater after performing SLOW RT compared to FAST. Practical Applications: Resistance-trained individuals looking to optimize distal quadricep hypertrophy may benefit from SLOW RT when performing isolated knee-extension exercises.

Table 1 - Summary of study outcomes.

(1) Comparisons of Torque, Power, and Neuromuscular Function During Isokinetic Muscle Actions in Children Versus Adolescents

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

University of Nebraska-Lincoln

The examination of torque and power production across the velocity spectrum may provide useful information regarding changes in muscle function during growth and development. Recent evidence has suggested that differences in torque and power production across velocity may reflect differences in neuromuscular function between children and adolescents. Purpose: The purpose of this study was to examine peak torque (PT), mean power (MP), electromyographic (EMG) amplitude, mechanomyographic (MMG) amplitude, and neuromuscular efficiency from EMG and MMG amplitude (NMEEMG and NMEMMG, respectively) across the isokinetic velocity spectrum in children versus adolescents. Methods: Nineteen males (mean ± 95% confidence interval, age = 12.62 ± 0.89 y) and 20 females (age = 12.43 ± 0.96 y) participated in this study and were classified as children (n = 8 males, n = 9 females) if their age was <12-years or adolescent (n = 11 males, n = 11 females) if their age was ≥12-years. Subjects completed maximal isokinetic leg extension muscle actions at 60, 120, 180, 240, and 300°·s−1. PT, MP, EMG amplitude, and MMG amplitude were quantified during all muscle actions. NMEEMG and NMEMMG were quantified by expressing PT relative to EMG and MMG amplitude, respectively, for each muscle action. Six separate three-way, mixed factorial ANOVAs (group [child vs. adolescent) × sex [male vs. female] × velocity [60,120,180,240,300°·s−1]) compared mean values for PT, MP, EMG amplitude, MMG amplitude, NMEEMG, and NMEMMG. Results: PT, MP, NMEEMG, and NMEMMG were greater for the adolescents than the children collapsed across sex and velocity (p ≤ 0.021). For the adolescents, PT decreased systematically across velocity (p ≤ 0.002), while MP increased from 60 to 240°·s−1 (p < 0.001) then plateaued to 300°·s−1 (p = 0.054). For the children, PT decreased from 60 to 240°·s−1 (p ≤ 0.041) then plateaued to 300°·s−1 (p = 0.148), while MP increased from 60 to 180°·s−1 (p ≤ 0.007), plateaued from 180 to 240°·s−1 (p = 0.158), then decreased from 240 to 300°·s−1 (p < 0.001). There were no group-, sex-, or velocity-related differences for EMG amplitude (p ≥ 0.051), while MMG amplitude increased from 60 to 240°·s−1 (p < 0.001) then decreased from 240 to 300°·s−1 (p < 0.001) collapsed across group and sex. NMEEMG increased from 60 to 180°·s−1 (p ≤ 0.014), then plateaued from 180 to 300°·s−1 (p ≥ 0.245), while NMEMMG increased from 60 to 240°·s−1 (p < 0.001) then plateaued to 300°·s−1 (p = 0.949) collapsed across group and sex. Conclusions: The main findings of this study demonstrated greater PT, MP, NMEEMG, and NMEMMG for adolescents than children across velocity. Furthermore, velocity-related patterns for EMG and MMG amplitude, which are thought to globally reflect muscle activation and motor unit recruitment, respectively, were similar for children and adolescents. However, when PT was expressed relative to EMG and MMG amplitude (NMEEMG and NMEMMG, respectively), differences between children and adolescents emerged. Interestingly, as demonstrated previously, velocity-related changes in MMG amplitude, NMEEMG, and NMEMMG seemed to closely track changes in MP across velocity. Practical Applications: Overall, regardless of velocity, the expression of PT relative to EMG and MMG amplitude (NMEEMG and NMEMMG, respectively), in conjunction with measurements of isokinetic torque and power production, may provide practitioners a unique method of examining growth and development-related augmentations in neuromuscular efficiency.

(2) The Effects of an Intensive Cycle Training Camp on Inter-Limb Asymmetry in Race Across America (RAAM) Athletes

J. Cree

Middlesex University, London

Purpose: There is little evidence investigating the effects of an intensive cycle training camp, designed to induce fatigue on inter-limb asymmetry. Single sided power meters are the most affordable method of power data collection for cyclists. If large changes in interlimb asymmetry are detected, and athletes are using a single-sided power meter to measure power output for training intensity, the live data and subsequently resulting session output data may be questionable. Therefore, the purpose of this poster is to investigate the variability of inter-limb asymmetries over the course of an intensive cycle training camp. Methods: 8 Race Across America (RAAM) winning athletes (Age: 49 ± 6.8; Height 165.2 ± 41.8 cm, Weight: 81.5 ± 14.1 kg) participated in a 7-day intensive warm-weather training camp in the lead up to the annual RAAM event. A standardized dynamic warm-up was conducted before each session, in addition, 3 practice trials at 60, 80, and 100% perceived effort were performed. Two minutes of rest was provided after the final warm-up trial was provided. Daily unilateral countermovement jump measures were collected pre-ride (3 trials each leg), and resulting scores expressed as mean and SD. Intraclass correlation coefficient (ICC) with absolute agreement was used for reliability and standard error of measurement calculated. Interlimb asymmetries were quantified as a percentage difference between limbs (from the average of 3 trials) using the formula proposed by Bishop et al. (2019), with asymmetries over 10% being identified as a potential issue (Bishop et al. 2017). Finally effect size (Cohen's-d) was used to determine the magnitude of change from day 1 baseline data using Equation 1.

Equation 1. Effect size (d) calculation

d = (Mgroup1 – Mgroup2)/SDpooled

Where SDpooled = √([SD2group1 + SD2group2]/2). Results: It is evident from the data that statistically significant changes in mean inter-limb asymmetry scores occurred daily large variation. Graph 1 provides visual representation of the variability in inter-limb asymmetry scores (%) per-athlete, per day. Evidently, a number of athletes break the 10% threshold, with one athlete changing from dominant right to non-dominant left sides. This shows the highly variable nature of inter limb asymmetry, bearing in mind the high reliability of the data, shown within the ICC. Conclusions: The effects of fatigue due to intensive cycle training are athlete specific and highly variable over the course of an intensive training period. However, based on the magnitude of change (Cohen's-d), asymmetry data is not sensitive enough to detect change, demonstrated through trivial effect sizes and large variances in standard deviation. Limb dominance from unilateral CMJ scores may be more reliable. Practical Applications: This investigation may highlight the need for daily calibration of single-sided power meters based on unilateral CMJ scores.

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Graph 1.:
Daily changes in asymmetry scores per person, over 7-day intensive cycle training camp. Data demonstrates highly variable changes in interlimb asymmetry scores on an individual bases, above the 10% threshold, not detectable when using daily mean averages.

(3) The Effect of Short-Term Cyle-Based High Intensity Interval Training on Quadriceps Muscle Volume

K. Wohlgemuth,1 J. Mota,2 P. Chen,3 L. Arieta,1 K. Kennedy,1 H. Giuliani,1 T. Blackburn,1 B. Pietrosimone,1 A. Smith-Ryan,1 D. Couper,1 and E. Ryan1

1University of North Carolina at Chapel Hill;2University of Alabama; and3The University of North Carolina at Chapel Hill

High intensity interval training (HIIT) is a popular mode of exercise characterized by short (e.g., 1 minute) work:rest ratios, resulting in improved cardiorespiratory fitness in just a few weeks. Although short-term resistance training programs have demonstrated noticeable changes in neuromuscular function, limited data exists regarding the influence of HIIT on changes in muscle size (e.g., muscle volume). Purpose: The purpose of this study was to investigate the influence of a brief (3 weeks) cycle based HIIT program on quadriceps muscle volume. Methods: Twenty-three healthy, previously untrained, young adults (14 women; mean ± SD, age = 24 ± 5 years; BMI = 23.39 ± 3.36 kg/m2) were randomized into intervention (n = 13) or control (n = 10) groups and came into the laboratory for testing on 2 separate occasions (pre, post), separated by approximately 20 days. All subjects underwent a cycle based, ramped V̇o2 assessment at pre-testing and had muscle volume assessed on both testing days. To examine muscle volume, each subject had the anatomical cross sectional area (ACSA) of their vastus lateralis assessed using brightness-mode ultrasound at 25, 50, and 75% of the length of the muscle while lying prone on a table. Muscle volume was estimated using the truncated cone technique, which assumes a conical shape of the muscle between available slices (e.g., 25–50% ACSA scans). A cycle based, maximal oxygen consumption test (V̇o2 max) protocol was completed at pre-test in order to determine peak power, which was used to program the twice weekly, three-week HIIT intervention. Each training session included 9 sets of 1 × 1 minute exercise at 90% peak power, with a 10th set performed until volitional failure. Subsequent training session wattage was increased by 7%, if the subject could cycle for ≥75 seconds on the 10th set. To examine the effects of the intervention on the change in muscle volume, an analysis of covariance (ANCOVA) was implemented to examine group (intervention, control) effects on the outcome variable (change score), while covarying for pre-test values. The alpha level was set at p ≤ 0.05, with 95% confidence intervals (CI), estimated marginal means, and the partial eta squared (η2) effect size statistic were also calculated. Results: When adjusting for pre-test values, there was a significant group effect present (F = 5.03; p = 0.036; η2 = 0.201) on the post-pre change score. Specifically, the change in muscle volume was significantly higher for the intervention (26.22 cm3; 95% CI = 6.84–45.60) compared to the control (−5.40 cm3; 95% CI = −27.49 - 16.70) group. Conclusions: Our findings suggest that 3 weeks of bi-weekly cycle based HIIT improved vastus lateralis muscle volume in healthy, previously untrained, young adults. Practical Applications: These findings may be attractive to the strength and conditioning practitioner, as cycle based HIIT is a time-efficient, single exercise modality that can simultaneously improve muscle size and cardiorespiratory fitness.

(4) Physiological and Kinematic Responses of Collegiate Rowers to Rowing on 2 Types of Rowing Ergometers

J. White,1 and M. Jones2

1Ohio University; and2George Mason University

Background: Physiological, metabolic, and biomechanical responses to submaximal and maximal exercise on the type D rowing ergometer (erg) have been established. The same comparisons have not been made with the dynamic (DYN) rowing erg, which was designed to simulate rowing on the water for proper training of competitive rowers. Design changes of the DYN erg include a moveable footrest and reduced handle return tension; however, the effect of these changes on rowing kinematics of trained rowers is unknown. Purpose: To compare physiological and kinematic responses to submaximal and maximal exercise on 2 rowing ergometers (DYN and type D) in trained collegiate rowers. Methods: National Collegiate Athletic Association Division I women rowers (n = 11, mean ± SD, age: 20.1 ± 1.3 years; 2,000-meter erg time: 474.76 ± 26.6 seconds) with a minimum of 3 years rowing experience volunteered to participate in the randomized, crossover design. Session 1 consisted of familiarization with rowing on the DYN and anthropometric measures. Sessions 2 and 3 were separated by 48 hours and completed in randomized order (DYN, type D). Rowers performed an incremental rowing test with the starting intensity determined from each athlete's most recent 2,000-meter type D erg time. Each stage of 7 lasted 4 minutes and wattage was increased 10–20 watts for each stage, with submaximal wattages the same for both tests. The last stage was maximal effort and the rower was instructed to cover as much distance as possible. Expired gases were collected to assess oxygen consumption (V̇o2) and ventilation (Ve). Heart rate (HR) was measured via portable wireless HR monitor. An eight-camera motion acquisition system tracked 30 markers placed on body landmarks in order to generate a biomechanical model of thoracic displacement. Paired t-tests were utilized to compare submaximal and peak physiological variables (HR, V̇o2, Ve) and rating of perceived exertion (RPE) between the DYN and type D erg tests (p = 0.05). At the maximal effort stage, paired t -tests were used to compare stroke rating (SR), stroke length, thoracic displacement angle, meters covered, and average watts (p = 0.05). Results: Height was 172.9 ± 8.1 cm and mass 69.2 ± 13.4 kg. There was no difference in the responses of HR, RPE, V̇o2, Ve, watts, or meters covered between the 2 ergs during submaximal and maximal stages. On the DYN, rowers had higher maximal stage SR (32.5/min vs. 40.5/min, p = 0.02), yet there was no difference between the thoracic displacements (DYN 25.2 ± 13.2°, type D 26.5 ± 4.7°, p = 0.74). Stroke length was significantly decreased on the DYN (0.8 ± 0.1 m) compared to the type D (1.4 ± 0.1 m) at the maximal stage (p < 0.001). Conclusions: No Ve, HR, V̇o2, or RPE differences were observed during the maximal stage. During the maximal stage effort the stroke rate was higher on the DYN while the stroke length was higher on type D. Practical Applications: Previous literature has suggested increased stroke rates may decrease the stress on lower back soft tissue. Furthermore, studies have suggested longer stroke lengths are a possible risk factor for injury to the soft tissue. The kinematic results of trained rowers from both erg types indicate that the DYN may reduce injury risk as compared to the type D.

(5) Differences in Electromyographic Amplitude Versus Torque Relationship in Younger Versus Post-Menopausal Women May Be Due to Differences in Muscle Mass

N. Banks,1 E. Rogers,1 T. Muddle,1 R. Colquhoun,2 and N. Jenkins1

1Oklahoma State University; and2University of South Alabama

Loss of muscle strength is accelerated in women due to menopause. Both reductions in skeletal muscle mass and neuromuscular function are thought to contribute to reductions in age associated losses in muscular strength. Purpose: The purpose of this investigation was to examine differences in muscle mass and strength, as well as the electromyographic versus torque relationship (EMG-T) in younger versus post-menopausal women, and explore whether skeletal muscle mass was related to EMG-T and strength across the sample. Methods: Thirty healthy young (age = 20 ± 3 years) and thirty healthy post-menopausal (56 ± 5 years, years post-menopause = 7 ± 4 years) females had vastus lateralis (VL) muscle cross sectional area (mCSA) and skeletal muscle mass (SMM) assessed with ultrasound and bioelectrical impedance analysis. Subjects also completed maximal voluntary isometric knee-extension tests, and then performed isometric ramp contractions at 40 and 70% of maximal voluntary isometric torque (MVIT). During the ramp contractions, EMG signals were collected from the VL to quantify EMG amplitude, which was regressed against torque and used to provide an EMG-T slope (Slope40/70) and intercept (Intercept40/70) for each subject at both 40 and 70% MVIC. Differences among age-groups were assessed with independent samples t-tests, while relationships were examined after partialling out body weight, because body weight has been shown to exert a substantial influence on neuromuscular outcomes and displayed collinearity with the dependent variables in this study. Mean ± 95% confidence interval difference scores are provided for variables that were different among age-groups. Results: Younger women had greater mCSA (+5.5 ± 1.1 cm2; p < 0.001), SMM (+2.2 ± 1.5 kg; p = 0.004), MVIT (+17.1 ± 16.3 Nm; p = 0.04), Slope40 (+0.003 ± 0.002 mV; p = 0.008), Slope70 (+0.003 ± 0.003 mV; p = 0.004), and lower Intercept40 (−0.01 ± 0.01 mV·%MVIT−1; p = 0.046) and Intercept70 (−0.03 ± 0.03 mV·%MVIT−1; p = 0.001) MVIT. The relationships among the dependent variables after partialling out body weight are included in Table 1. Conclusions: The results of this study indicate that the young females exhibited more positive slopes and lower y-intercepts of the EMG-Torque relationship during ramp contractions at both 40 and 70% MVIT, when compared to their post-menopausal female counterparts. We also observed greater MVIT, SMM, and mCSA in the young versus post-menopausal women, which, after controlling for body weight, were consistently related to the assessments of neuromuscular function. Practical Applications: Post-menopausal women experience significant reductions in muscle mass and neuromuscular function. Our data suggest that muscle mass is likely a significant contributor to the declines in neuromuscular function observed in these women, suggesting that the preservation of muscle mass should be a primary goal for women in the years leading up to, during, and immediately after menopause.

Table 1 - Pearson's partial correlation coefficients among the dependent variables after partialling out body weight.
*p ≤ 0.05; #p ≤ 0.01; †p ≤ 0.001; SMM = skeletal muscle mass; MVIC = maximal voluntary isometric contraction; mCSA = mean cross sectional area.

(6) Acute Maximal Eccentric and Concentric Exercise Cause Similar and Substantial Central and Peripheral Fatigue of the Elbow Flexors

S. Fleming,1 R. Colquhoun,1 M. Magrini,2 N. Banks,3 E. Rogers,3 and N. Jenkins3

1University of South Alabama;2Creighton University; and3Oklahoma State University

Purpose: The purpose of the present study was to examine the contributions of central and peripheral properties of the elbow flexor musculature before and immediately following acute bouts of maximal eccentric (ECC) and maximal concentric (CON) contractions. Methods: Fifteen strength-trained males (mean ± SD, age = 23 ± 2 years) completed 6 sets of 10 repetitions of ECC and CON contractions of the elbow flexor musculature through a ∼90° range of motion. The order and arm utilized was randomized for each subject and 2 minutes of rest were given between each set. Subjects were seated in an isokinetic dynamometer, with force recorded from a load cell attached to a custom-built handle on the arm of the dynamometer. Peripheral nerve stimulation was utilized to measure voluntary activation (VA) and evoked peak twitch force (PT) prior to (PRE) and immediately post-exercise (POST). All signals were recorded via a Delsys Bagnoli acquisition unit. All visits took place at the same time of day (±1 hour) and each visit was separated by 6 ± 1 day. All variables were calculated offline using custom-written software. Separate 2 (Condition) × 2 (Time) repeated-measures ANOVAs were run to examine any potential differences in dependent variables. All statistical analyses were run in SPSS (v. 23, IBM, Inc., Armonk, NY, USA) with an a priori Type I error rate of 5%. Results: No Condition × Time interactions were found for VA (p = 0.175) or PT (p = 0.359). Significant main effects for Time were found for VA (PRE: 99.3 ± 1.7%; POST: 85.1 ± 16.3%; p = 0.004) and PT (PRE: 36.4 ± 11.7 N; POST: 16.3 ± 9.5 N; p < 0.001). Additionally, a significant main effect for condition was found for PT (ECC: 22.4 ± 10.2 N; CON: 30.3 ± 11.6; p = 0.007). Conclusions: The results of the present study indicate significant reductions in VA and PT post-exercise, independent of contraction type. Our data suggest that maximal eccentric and concentric exercise bouts cause significant central and peripheral fatigue in the elbow flexors. Future research is needed to examine the recovery of these mechanisms at more prolonged periods of time (i.e., 48–72 hours post-exercise) to better understand the time course of recovery. Practical Applications: Fatigue from maximal effort exercise diminishes the voluntary and contractile twitch force regardless of contraction type. Coaches and practitioners should therefore plan proceeding activities appropriately to account for diminished neuromuscular capacity following maximal exercise.

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Figure 1.:
Voluntary activation (A) and peak twitch force (B) of the elbow flexor musculature immediately prior to and following maximal eccentric (ECC) or maximal concentric (CON) exercise. *Indicates significantly lower pooled POST, when compared to PRE

(7) Minimizing Interpulse Variability in Corticospinal Excitability: How Many TMS Pulses Are Optimal?

J. Pagan,1 K. Harmon,1 R. Girts,1 G. Rodriguez,1 R. MacLennan,2 J. Hernandez Sarabia,2 N. Coker,1 J. Carr,3 X. Ye4, J. DeFreitas,2 and M. Stock1

1University of Central Florida;2Oklahoma State University;3Southern Utah University; and4University of Mississippi

Transcranial magnetic stimulation (TMS) is a non-invasive technique that is commonly used in the fields of medicine and neuroscience to study cortical and subcortical plasticity. However, TMS results vary considerably both within and between individuals. Purpose: We sought to determine the optimal number and combination of TMS pulses needed to minimize variability in corticospinal excitability. Methods: Ten healthy, physically-active males (mean ± SD age = 23 ± 4 years; height = 175.4 ± 7.1 cm; mass = 77.2 ± 6.2 kg) visited the University of Central Florida Neuromuscular Plasticity Laboratory for testing. Isometric strength testing of the dominant knee extensors was performed with an isokinetic dynamometer (knee joint angle = 110°) while bipolar surface electromyographic (EMG) signals were detected from the rectus femoris. TMS assessments consisted of delivering pulses to the location over the motor homunculus which demonstrated the greatest EMG peak-to-peak amplitude (i.e., “hotspot”) while the subjects performed knee extension contractions at a torque output corresponding to 10% of their maximum. Visual feedback of each subject's torque output was provided on a computer monitor directly in front of them. Twenty pulses were delivered to the hotspot at a stimulator output corresponding to 130% of active motor threshold. Variability of different pulse combinations was examined with 2 statistical approaches. The first approach consisted of quantifying the coefficient of variation of motor evoked potential (MEP) amplitude for the first 3, 6, 10, 12, 15, and twenty pulses. The second approach involved sorting the twenty peak-to-peak amplitude values from lowest to highest and examining the coefficient of variation from only the middle 3, 6, 10, 12, and 15 pulses. Results: For the first approach, when examined qualitatively, 7 subjects demonstrated the lowest coefficient of variation in MEP amplitude when only 3 or 6 pulses were utilized. For 3 subjects, the MEP amplitude variability was lowest when including 10 or 12 pulses. Inclusion of ≥15 pulses introduced greater variability, with one subject demonstrating a coefficient of variation as high as 53.0%. Use of the second approach demonstrated that variability was reduced substantially by including only the middle 3 or 6 MEPs (range = 0.8–20.1%). Conclusions: In all cases, inclusion of ≥15 TMS pulses exacerbated MEP amplitude variability. Rather than analyzing MEPs based on their order of pulse delivery, variability in corticospinal excitability was dramatically reduced by removal of extreme values. Practical Applications: TMS is an attractive research tool that can be used to study neural adaptations to strength training. However, measures of corticospinal excitability vary substantially not only between individuals, but within a single testing session. Based on these findings, it is recommended that investigators take steps to minimize variability in TMS MEP outcomes.

(8) The Concurrent Validity of a Portable Bilateral Jump Mat to Estimate Countermovement and Squat Jump Performance

S. Guppy,1 J. Lake,2 Y. Kotani,3 C. Latella,3 J. Cochrane Wilkie,4 K. Kendall,3 and G. Haff3

1School of Medical and Health Sciences, Edith Cowan University;2University of Chichester;3Center for Exercise and Sports Science Research, Edith Cowan University; and4Center for Exercise and Sports Science Research, Edith Cowan University

Purpose: The purpose of this study was to assess the concurrent validity of a portable jump mat that measures flight-time for individual legs as well as overall flight-time against those calculated using bilateral, in-ground force plates during countermovement (CMJ) and squat jumps (SJ). Methods: Sixteen healthy subjects (age: 27.7 ± 4.3 years, height: 170.7 ± 10.6 cm, body mass: 75.7 ± 13.3 kg) performed a general dynamic warm-up of bodyweight lunges and squats followed by 3 submaximal CMJs and SJs. Next, subjects performed 6 maximal CMJs and SJs with one and 2 minutes of rest between trials and jump types, respectively, in a block randomized order. Prior to completing both jumping tasks subjects were instructed to jump “as high and as fast as possible”. All trials were performed while standing on a portable jump mat (EzeJump, Swift Performance, Brisbane, Australia) placed over 2 in-ground triaxial force plates sampling at 1000 Hz (Type 9287CA/9287BA, Kistler Instruments, Switzerland). The jump mat was interfaced with a tablet device (iPad 6, Apple Inc, USA) via Bluetooth. Left and right leg vertical ground reaction forces (including time off the force plates) were recorded via the 2 force plates. The jump-mat software calculated overall jump flight-time as well as the individual left- and right-leg flight-times. All force-time curve and flight-time data were exported to custom Excel spreadsheets for analysis. Jump height was estimated from flight-time calculated by both the bilateral force plates and the portable jump mat. To assess agreement between the 2 devices, ordinary least products regressions were calculated. Fixed bias was deemed to be present if the 95% confidence interval of the intercept did not include zero and proportional bias present if the 95% confidence interval of the slope did not include one. Results: No fixed or proportional bias was present for characteristics recorded in the SJ (Table 1). No fixed or proportional bias was present for CMJ jump height, overall flight-time and right-leg flight time. Fixed bias was present for left-leg flight time in the CMJ, but no proportional bias was present. Conclusions: The bilateral jump mat assessed in this study agrees with the calculation of flight-time and jump height using bilateral force plates during both CMJs and SJs. Additionally, individual limb flight-times calculated using the portable jump mat agree with those calculated using bilateral force plates in the SJ. Practical Applications: The EzeJump mat may be used by strength and conditioning professionals who do not have access to force plates, but still wish to assess jump height and inter-limb performance differences during jumping tasks.

Table 1 - Results of the least products regression between force plate and jump mat jump height, left and right and summed left and right flight time.
Note: fixed bias was present if the intercept 95% confidence limits (CL) did not include zero, and proportional bias was present if the slope and 95% CL did not include 1; † = fixed bias.

(9) Differences in Muscle Activity Utilizing 3 Hand Positions in the Front Squat

J. Taylor,1 J. Dean,1 M. Sommer,1 M. Morales,1 L. Maldonado,1 J. De Witt,2 and W. Amonette2

1University of Houston-Clear Lake; and2University of Houston - Clear Lake

Purpose: To describe differences in muscle activation patterns using front squats with 3 commonly prescribed style variations. Methods: Eight experienced weightlifters volunteered (6M:2F, 24.50 ± 3.00 y, 78.20 ± 12.30 kg, 173.10 ± 8.00 cm) to participate in this study. Inclusion criteria were a score above a 75% (60/80) in the Lower Extremity Functional Scale (LEFS) and familiarity with the front-rack (FR) front squat exercise, defined as performing the lift at least once every 2 weeks for the previous 6 months. Subjects were required to attend 2 sessions. During session one, subjects completed the LEFS, and we collected anthropometrics and a one-repetition maximum (1RM) in the FR front squat. We estimated a 1RM (body mass (kg) multiplied by 1.25 (males) or 0.90 (females)) and used NSCA 1RM protocols to obtain the actual value. During the second session, no sooner than one week after session one, we placed EMG electrodes on the subjects on the following muscles: posterior deltoid (PD), middle trapezius (MT), latissimus dorsi (LD), erector spinae (ES), gluteus maximus (GM), biceps femoris (BF), erector femoris (EF), and vastus medialis oblique (VMO). All electrode sites were shaved, abraded, and disinfected prior to placement of electrodes. Subjects were led through a standardized warm-up before performing 4 repetitions of each front squat variation at 50 and 80% of their 1RM. The order of grip variations was randomized. FR squats were performed from the catch position for the clean. Strap-assisted (SA) front squats were performed from the same position, but instead of wrapping the hands around the bar, subjects grasped a weightlifting strap secured to the bar. Cross-grip (CG) front squats were performed with the bar lying across the anterior deltoid, humerus flexed and internally rotated, with hands grasping the bar at the opposite shoulder. We analyzed the second repetition. We performed a three-way repeated measures analysis of variance with Tukey's post-hoc tests for within-subjects factors of grip (FR, SA, CG), load (50%1RM, 80%1RM), and phase of the front squat (0, 25, 50, 100%). All data was collected at 2000 Hz. Alpha <0.05. Results: Subjects reported 5.89 ± 4.00 years (mean ± sd) of training experience; 1RM: 114.10 ± 31.00 kg. At the bottom of the squat at 80%1RM, the activation (µV) of select upper-body muscles was: erector spinae (−7.05 × 10−5 ± 4.13 × 10−4); latissimus dorsi (9.00 × 10−6 ± 7.14 × 10−5); posterior deltoid (−7.00 × 10−7 ± 2.02 × 10−3); middle trapezius (−3.48 × 10−4 ± 2.22 × 10−3). There were no significant main effects for grip, load, or phase for all (p > 0.05) but one EMG site; for the biceps femoris, there was a significant main effect for phase (p = 0.02). For the biceps femoris, Tukey's post hoc tests showed significant differences across all pairwise phase comparisons (p < 0.001). Conclusions: Our findings suggest there was no significant difference in muscle activation of the PD, MT, LD, ES, GM, BF, EF and VMO across the 3 hand positions during the front squat. However, due to the high variability of EMG data these results should be considered with caution. Practical Applications: Strength and conditioning professionals should prescribe whichever variation of the front squat an athlete is comfortable with. Considerations should be made for prior injury or existing discomfort during different variations of the front squat.

(10) A Comparison of Reactive Strength Index Values Obtained From Countermovement and Rebound Jumps

J. Morgan, P. Comfort, T. Dos'Santos, and J. McMahon

University of Salford

The countermovement jump (CMJ) and multiple-repetition rebound jump (RJ) tests (usually, 3 or 5 repeated jumps) are routinely conducted with athletes to evaluate their neuromuscular function (NMF) and stretch-shortening cycle (SSC) ability, respectively. Jump height (JH), reactive strength index (RSI) and RSI modified (RSImod) are regularly reported for these purposes. The countermovement-rebound jump (CMRJ) involves a CMJ immediately followed by 1 RJ repetition, but it is unknown whether it can be utilized as an all-encompassing test that evaluates both NMF and SSC ability. Purpose: To compare RSImod and RSI, and their constituent parts, obtained from the CMJ, CMRJ, 3RJ and 5RJ tests. Methods: Twenty resistance-trained men performed 3 maximal-effort CMJs, CMRJs, 3RJs and 5RJs in a randomized order on a force plate (sampling at 1,000 Hz). The CMJs were performed to a self-selected depth (arms akimbo) with the intent to jump as fast and high as possible. The CMRJs were performed the same but instead of landing after the CMJ, a RJ was performed with the aim of minimizing contact time (CT) and maximizing JH. The 3RJs and 5RJs were comprised of a CMJ followed by 3 and 5 RJs (performed like RJ element of the CMRJ), respectively. CMJ start was identified using the criterion method. Take-off and touchdown for all jumps were identified when force fell below and then rose above 20 N, respectively. Time to take-off (TTT) for CMJs was calculated as time at take-off minus CMJ start time and CT for RJs was calculated as take-off time minus touchdown time. JH was estimated from flight time. RSImod for CMJs was calculated as JH divided by TTT and RSI for RJs was calculated as JH divided by CT. Results: JH was significantly greater (p = 0.003, d = 0.498) and TTT was significantly longer (p = 0.006, d = 0.267) for the CMJ when compared with the CMJ portion of the CMRJ. RSImod values were similar (p = 0.275, d = 0.165). For RJ portion of the CMRJ, JH was significantly greater than for both the 3RJ (p = 0.006 d = 0.499) and the 5RJ (p = 0.001, d = 0.690). The CT was only significantly longer for the CMRJ when compared to the 5RJ (p = 0.019, d = 0.302). However, as seen in Figure 1, RSI was significantly larger for the CMRJ when compared to both the 3RJ (p = 0.018, d = 0.275) and the 5RJ (p = 0.002, d = 0.401). Conclusions: CMJ strategy alters in the CMRJ in the direction of a shorter TTT and a lower JH. RJ strategy changes when performing increasing RJ repetitions (1, 3 or 5) in the direction of a lower JH and shorter CT, but lower RSI. Practical Application: It may be wise to conduct CMJ testing separately from RJ testing, especially if monitoring NMF whereby CMJ strategy is of interest given that it changed in the CMRJ test. However, the CMRJ test may be a suitable alternative to the 3RJ and 5RJ tests if monitoring SSC ability is of interest, as it yielded the highest RSI values due to a greater JH (∼2–3 cm) being attained with only a slightly longer (∼2–11 ms) but still a short (∼233 ms) CT.

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Figure 1.:
A comparison of reactive strength index (RSI) values obtained for the countermovement-rebound jump (CMRJ), the three-rebound jump (3RJ) and the five-rebound jump (5RJ) tests.

(11) Longitudinal Relationships Between Strength and Static Jump Asymmetries in Collegiate Soccer Players

K. Painter, L. Rodriguez-Castellano, K. Carroll, and M. Stone

East Tennessee State University

Several studies have linked asymmetries in bilateral jump performance to a potential risk of injury. Asymmetries have also been linked to maximal strength, suggesting that weaker athletes have greater asymmetry than stronger athletes. Purpose: To investigate the association between maximal strength and static jump (SJ) bilateral asymmetry in collegiate soccer players, along with the change over time. Methods: Athlete monitoring data from male (M, n = 9) and female (F, n = 9) NCAA Division-I soccer players were considered for this analysis. This retrospective analysis included SJ and isometric mid-thigh pull (IMTP) assessments and was approved by the university's Institutional Review Board. Baseline data (PRE) were collected in the pre-competitive period (i.e., fall semester). Athlete data were collected again in the pre-competitive period (POST), 2 years after the initial collection. In the interim, athletes participated in both soccer and strength & conditioning activities consistently. Each athlete followed the same standardized warm-up protocol during each testing session, then performed 2 maximal effort trials of both the SJ and IMTP. Symmetry index score (SI) was calculated using unilateral peak force values during the take-off phase of the jump (Eq. 1). To assess maximal strength, allometrically-scaled isometric peak force (IPFa) was calculated from the IMTP test. Data from the 2 maximal effort trials were averaged together for analysis. Equation 1: SI = (Left Force Value − Right Force Value/Left Force Value + Right Force Value) × 100

To analyze results, a 2 × 2 mixed design ANOVA (group × time) was used. When statistically significant main effects were observed, a Holm-Bonferroni post hoc adjustment was used. Pairwise comparisons were further assessed using Cohen's d effect sizes (ES). Pearson's correlations were used to quantify the relationship between the SI and IPFa change scores. Results: Mean IPFa values increased from PRE (M = 207.1 ± 31.3 N·kg−2/3; F = 145.8 ± 28.1 N·kg−2/3) to POST (M = 218.5 ± 21.7 N·kg−2/3; F = 169.3 ± 12.8 N·kg−2/3). Statistically significant main effects for time (PRE-POST) and group (M and F) for IPFa were observed (p = 0.016, p < 0.001; respectively) with a moderate change magnitude (d = 0.635). Mean POST SI (2.9 ± 3.4%) indicated greater asymmetry compared to PRE (1.3 ± 3.0%). PRE to POST differences in SI were statistically significant (p = 0.012) with no statistical differences between M and F. Static jump heights were significantly different between M and F (p < 0.001), but no significant changes occurred from PRE to POST. Moderate negative correlations were found between IPFa and absolute SI differences (r = −0. 472, p = 0.048). Conclusions: Moderate correlations in IPFa and SI changes suggest strength does play a role in deterring asymmetry. However, increases in SI from PRE to POST does support the possibility of functional asymmetries developing in soccer players. While IPFa improved, F had a greater change from PRE to POST (d = 0.602) than M (d = 0.292), possibly due to the lower baseline levels of strength. Overall, more in-depth longitudinal observations are needed to ascertain the true relationship between SI and IPFa across time in soccer players. Practical Applications: Soccer athletes are prone to develop some functional asymmetries. Further development of strength and non-dominant side usage in both M and F soccer players may reduce a potential risk of injury from asymmetry over time.

Thursday, July 9, 2020, 12:00 pm–1:30 pm

(12) Examination of Motor Unit Action Potential Amplitude as a Non-Invasive Indicator of Motor-Unit Specific Hypertrophy in Females

E. Rogers,1 N. Banks,1 T. Muddle,1 R. Colquhoun,2 and N. Jenkins1

1Oklahoma State University; and2University of South Alabama

Purpose: This study examined the utility of the motor unit action potential amplitude (MUAPAMP) versus recruitment threshold (RT) relationship as a non-invasive indicator of motor unit specific hypertrophy in females in response to an 8-week, high-intensity exercise training intervention. Methods: Twenty-seven young, inactive females (age = 21 ± 3 years) completed either an 8-week control (CON; n = 18) or exercise (EX; n = 9) condition. The EX group performed 2 high-intensity interval training sessions and 2 resistance training sessions per week for 8 weeks, while the control group was asked not to change their physical activity habits. Before (PRE) and after (POST) the intervention period, muscle cross sectional area (mCSA) of the vastus lateralis (VL) was determined via ultrasound, and the MUAPAMP vs. RT relationship was examined using high density surface electromyographic signals from the VL of each subject during an isometric ramp contraction at 70% of maximal voluntary isometric torque (MVIT). Two-way, mixed-factorial ANOVAs were used to assess the influence of the intervention on mCSA and the slope and intercept of the MUAPAMP vs. RT relationship. In addition, Pearson's product-moment correlation coefficients were used to examine the relationships between every subject's change (i.e., Post—Pre) in MUAPAMP vs. RT slope and y-intercept, and VL mCSA. Mean ± SD values are reported for MU characteristics and, when appropriate, the mean ± 95% confidence interval change scores are reported for significant PRE to POST changes. Results: On average, we detected 20.9 ± 8.5 and 23.0 ± 7.9 motor units (MUs) per contraction at PRE and POST, respectively. The average RT range for these MUs was 24.4 ± 10.5% and 31.8 ± 10.5% at PRE and POST, respectively. Further, MUAPAMP and RT were strongly significantly related for all subjects at PRE (r = 0.83 ± 0.9) and POST (r = 0.86 ± 0.8). There were Condition Time interactions for mCSA (F1,25 = 17.9; p = 0.0003), and MUAPAMP vs. RT slope (F1,25 = 12.1; p = 0.0019) and intercept (F1,25 = 5.58; p = 0.026). Both mCSA (+2.3 ± 1.0 cm2) and MUAPAMP vs. RT slope (+1.5 ± 1.4 µV·MVIC%−1) increased significantly (p ≤ 0.04) in the EX group. There was no change in mCSA in the CON group (p = 0.96), but MUAPAMP vs. RT slope decreased (−1.1 ± 1.0 µV·MVIC%−1; p = 0.03). Post-hoc comparisons revealed no significant changes from PRE to POST for MUAPAMP vs. RT intercept in either group (p ≥ 0.18). The correlations revealed a significant relationship between the change in MUAPAMP vs. RT slope and the change in mCSA in the EX (r = 0.68, p = 0.046), but not CON (r = 0.12, p = 0.76) group. Conclusions: Both the slope of the MUAPAMP vs. RT relationship and mCSA of the VL increased in response to 8 weeks of high-intensity exercise training in females. The increase in MUAPAMP vs. RT slope suggests a preferential increase in the size of high threshold motor units in response to 8 weeks of high-intensity exercise training. Further, there was a strong relationship between the changes in each of these variables. Practical Applications: These data suggest that the electrophysiological information gathered from high density surface electromyographic signals during an isometric contraction at 70% MVIT may provide non-invasive information regarding motor unit specific hypertrophy following high-intensity exercise interventions in females.

(13) Effects of the Aquatic Environment on Maximal Isometric Muscle Strength and Rate of Force Development

M. Vakula, E. Bressel, and Y. Kim

Utah State University

Due to the unique properties, the aquatic environment provides, previous studies have tested the impact of the aquatic environment on strength and function as compared to land. Recently, we reported that a group of young-adults seated in chest-deep water elicited higher peak grip strength than a matched control group. Suggesting, grip strength is greater in an aquatic environment than land, however, our result was limited to a single measurement of peak strength and between-group differences. Therefore, the effect the aquatic environment has on other measures of strength such as the rate of force development is unclear. Purpose: The purpose of this study was to investigate the effects of an aquatic environment on peak isometric force and rate of force development during a mid-thigh pull exercise as compared to a land environment. Methods: Seven healthy college students participated in this study (27.4 ± 1.6 years). Aquatic and land conditions were delivered in a randomized order during 2 visits separated by 24 hours. Subjects were immersed in thermoneutral water to the xiphoid process as they stood atop a waterproof force platform during the aquatic condition. Peak force, early (RFD100) and late (RFD200) rate of force development during the mid-thigh pull were calculated from ground reaction force data. A paired-samples t-test (α = 0.05) was used to calculated differences between the land and the aquatic environment. Results: In comparison to the land environment, there were no differences in isometric peak force (1,298.9 ± 719.4 N vs. 1,359.89 ± 622.4 N, p = 0.605) and RFD100 (7,342.4 ± 5,292.9 N vs. 7,857.0 ± 4,394.9 N, p = 0.559) in the aquatic environment. Conversely, RFD200 (9,158.1 ± 4,733.0 N vs. 5,496.2 ± 2,631.5 N, p = 0.009) was greater during the land condition in comparison to the aquatic condition. Conclusions: The results suggest that the aquatic and land environment may have different effects on isometric muscle strength. Contrary to our previous findings, the aquatic environment did not have an effect on maximal strength. This suggests that the reproducibility of measurements in the aquatic environment needs to be further evaluated. Future studies involving a large sample size and additional measures of strength are needed to confirm our findings. Practical Applications: Overall, our findings suggest that peak force and rate of force development are comparable in an aquatic environment compared to a traditional land environment. Thus, individuals with preferences for the aquatic environment during strength training will not sacrifice their capacity for peak and rate of force development during training.

(14) Drop Jumps With Increased Cognitive Demand Influence Leg Stiffness, Jump Height and Ground Contact Time

H. Holmes, J. Downs, and J. Roper

Auburn University

Drop jumps (DJ) serve many purposes, including training the stretch shortening cycle, assessing athletic performance and understanding neuromuscular control during landing. Leg stiffness is neuromuscular control measure relevant in coaching due to associations with athletic performance and accessible performance measures, like ground contact time. However, cognitive demands utilized in many sports (i.e., reaction time, decision-making) may influence DJ landing mechanics. Thus, assessing how added cognition during DJs influences leg stiffness, ground contact time and jump height may provide more realistic performance interpretations for sporting environments. Purpose: To identify relationships and differences among leg stiffness, ground contact time and jump height during DJs with concurrent decision-making demands. Methods: Healthy, active subjects (n = 30, age: 20 yr ± 1 year, height: 1.71 m ± 0.14 m, mass:69.8 kg ± 11 kg) performed DJs and drop lands (DL) under 4 conditions from a 1 ft box placed 1/2 the subject's height from force plates. The standard condition involved asking subjects to perform a DJ or DL. The choice condition allowed subjects to volitionally choose between a DJ or DL. Visual and auditory conditions involved decision-making through reactions to visual or auditory cues presented while the subject was in mid-air. Three jumps and 1 land were randomized in each condition. Leg stiffness equaled the ratio of peak vertical ground reaction force and change in leg length between foot strike and time of minimum leg length. Leg length equaled the distance between the lateral malleolus and greater trochanter. Ground contacts were identified with a 5N threshold and jump height was determined by center of mass displacement. A one-way repeated measures MANOVA with a post-hoc Bonferroni adjustment (α = 0.016) identified differences in outcome variables among conditions. Pearson Product correlations were performed among dependent variables within conditions. Results from DJs are reported as M ± SD.Results: There was a significant effect of decision-making on DJ dependent variables ( = 0.457, F(9,207.018) = 8.741, p< 0.001). Audio DJs exhibited greater leg stiffness (220.3N/mkg ± 84.2N/mkg) than standard DJs (197N/mkg ± 72.2N/mkg, p = 0.002). Auditory DJs exhibited longer ground contact times (0.63 s ± 0.13 s) compared to visual (0.57 s ± 0.09 s, p< 0.001), choice (0.55 s ± 0.11 s, p< 0.001) and standard (0.53 s ± 0.10 s, p< 0.001) DJs. Jump height was decreased in visual DJs (0.42 m ± 0.09 m) compared to standard DJs (0.45 m ± 0.94 m, p = 0.004). Leg stiffness was inversely related to ground contact time in the standard (r = −0.523, p = 0.003) and choice (r = −0.383, p = 0.037) conditions only. Conclusions: Decreasing time to pre-plan movements with reactive decision-making may alter neuromuscular control contributing to DJ performance. Increased ground contact time and leg stiffness during auditory DJs and decreased jump height during visual DJs indicate specific cue type may be important in assessing DJ performance. Practical Application: Incorporating sports-relevant cognition with DJs may improve translation of training into sporting environments. Assessing how athletes' respond with and without different cues during DJs may provide enhanced, individualized information for coaches useful in designing sports-specific programs.

(15) Reliability and Repeatability of Ultrasound Muscle Pennation Angle at Several Common Measurement Locations in the Quadriceps Femoris

A. Harrison, T. Martin, J. Garner, and J. Mouser

Troy University

Using B-mode ultrasound to measure skeletal muscle architecture is a common practice in sport science research. One such measure, muscle fascicle pennation angle, is often utilized to determine architectural changes in skeletal muscle (e.g., quadriceps femoris) following a period of lower body resistance training. There are many different measurement locations reported in the literature, but typically a lack of agreement or cohesion between reported measures. Purpose: The purpose of this study was to determine the reliability of the most commonly reported measurement locations in 3 of the 4 quadriceps muscles, including the vastus lateralis, rectus femoris and the vastus medialis. Methods: Six male and female subjects (n = 12)) (mean ± SD): age 21.4 ± 1.2 years, height 1.71 ± 0.08 m, body mass 86.7 ± 25.0 kg, volunteered for this study. The protocol consisted of 2 separate visits one week apart. Subjects visited the laboratory and rested in the supine position for 15 minutes. Measurement locations on the anterior leg (33, 50, and 66% the distance between the anterior superior iliac spine [ASIS] and the superior border of the patella [ANT33, ANT50, ANT66, respectively]), lateral leg (33, 50, and 66% the distance between the greater trochanter and the lateral condyle [LC] of the femur [LAT33, LAT50, LAT66, respectively], 66% the distance between the ASIS and the LC [VL66]), and medial leg (80% the distance between the ASIS and the medial condyle of the femur [VM80]) were marked and recorded. Two ultrasound images were recorded at each location per visit. Muscle fascicle pennation angle was measured using on-screen calipers. A single researcher performed all ultrasound and pennation angle measurements. Intraclass Correlation Coefficient (ICC) analyses were performed on all 4 measures at each of the 8 locations. Results: Muscle fascicle pennation angle ranged from (mean ± SD) 14.5° ± 3.6° at ANT66 to 29.5° ± 6.4° at VM80. Pennation angle measurements were easily obtainable in 4 of the 8 measurement locations (ANT33, ANT50, ANT66, VL66) in all 12 subjects. LAT33 measurements were obtainable in only 7 of 12 subjects. ICCs ranged from a low of 0.623 (0.064–0.920) at ANT66 (p = 0.020) to a high of 0.862 (0.619–0.965) at LAT50 (p < 0.0005). Conclusions: Most measurement locations were shown reliable in the determination of muscle fascicle pennation angle. However, several measurements were not possible in some subjects, likely due to individual variation in muscle size and the anatomical orientation of the muscle. Absolute measures of location (e.g., 66% of the distance between 2 anatomical landmarks) may reduce reliability in measurement when applied to groups of people. Researchers should consider individualized measurement locations for each subject when performing repeated measures of muscle fascicle pennation angle. Practical Application: When tracking changes in skeletal muscle architecture, measurement locations that are relative to the person should be used to ensure that all measurements are possible.

(16) Vastus Lateralis Mechanomyography and Estimated Blood Flow During Sub-Maximal Voluntary Isometric Leg Extension Muscle Actions

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

University of Nebraska-Lincoln

Background: It has been hypothesized that the surface mechanomyography (MMG) signal quantifies the low-frequency lateral oscillations of muscle fibers during contraction, which may be influenced by viscosity of the muscle and fluid surrounding the muscle fibers. Total hemoglobin + myoglobin (total[heme]) as assessed by near-infrared spectroscopy (NIRS) has been suggested to provide an estimate of muscle blood flow, which may be related to the theory that fluid mechanics contribute to the MMG signal. Purpose: Examine total [heme] patterns of response in relation to MMG amplitude of the vastus lateralis during submaximal (10–90%) and maximal voluntary isometric contractions (MVIC) of the leg extensors. Methods: 12 active males (mean ± SD: age: 23 ± 3 years, mass: 81.5 ± 15.2 kg, stature: 180.9 ± 7.2 cm) completed 3, 5 s MVICs and 5 s submaximal randomly-ordered isometric step leg extension muscle actions in 10% increments from 10—90% of the MVIC. Surface MMG signals were detected using an accelerometer placed on the vastus lateralis, proximal to the NIRS device. MMG signals (m·s−2) and NIRS-measured relative concentration changes (Δ μM) in total [heme] were recorded simultaneously and quantified for the same 0.5 s epochs during the isometric force plateaus. MMG amplitude was calculated and normalized to the MVIC. Results: Torque values of MVIC ranged from 129—308 Nm. MMG amplitude increased steadily from 10 to 40% (p < 0.001–0.036), remained the same from 40 to 50% (p = 0.176), increased from 50 to 60% (p = 0.002), and then plateaued from 60 to 90% MVIC (p = 0.284–0.600) (Figure 1). With a similar, but inverse pattern, total [heme] decreased from 20—40% (p = 0.002–0.003), remained the same from 40—50% (p = 0.723), and decreased to 80% MVIC (p = 0.001–0.032) (Figure 1). Conclusions: The pattern of total [heme] changes during incremental isometric muscle actions of the vastus lateralis indicated that oxygenated blood was progressively diminished from the muscle until 80% MVIC. Yet, MMG amplitude progressively increased until 60% MVIC. Thus, despite less blood in the muscle, muscle sounds as reflected by MMG amplitude still increased. These data challenge the hypothesis of fluid mechanics as a mechanism underlying the mechanomyogram. Interestingly, these data also challenge the hypothesis that isometric muscle actions of relatively low intensity occlude blood flow to the muscle, since total [heme] continued to decrease until 80% MVIC. Practical Application: Skeletal muscle blood flow and resulting fluid mechanics seem to be unlikely contributors to the mechanomyogram in contrast to previous hypotheses. Furthermore, oxygenated blood was not fully eliminated from the vastus lateralis until at least 80% MVIC, which may have implications regarding fatigue during isometric muscle actions.

F5
Figure 1.:
Patterns of response for MMG amplitude and changes in total [heme] of the vastus lateralis during submaximal isometric voluntary contractions. MMG amplitude increased from 10 to 40%, held constant from 40 to 50%, increased to 60%, and then plateaued from 60 to 90% MVIC. Total [heme] followed a similar, but inverse pattern by decreasing from 20 to 40%, held constant from 40 to 50%, and then decreased to 80% MVIC.

(17) Lean Mass Asymmetry Is Weakly Associated With Jumping Performance in NCAA Division I Basketball Players

C. Bailey, R. Eusufzai, and A. Wright

University of North Texas

Asymmetry measurement in sport performance has been popular in recent research. Studies have demonstrated a potential link to performance decrements in vertical jumping with increasing force production asymmetry. To the current authors' knowledge, only one study has investigated the influence lean mass asymmetry has on jumping performance and found performance decrements, but lean mass asymmetry only accounted for a small portion of the variance in jumping performance. Purpose: The purpose of this study was to evaluate the association between lean mass asymmetry and jumping performance in NCAA Division I basketball players. Methods: 12 male NCAA Division I basketball players volunteered for this study (age = 21.8 ± 1.2 years, height = 1.9 ± 0.1 m, body mass = 85.9 ± 9.1 kg). Athletes completed body composition assessment via dual energy x-ray absorptiometry (GE Lunar iDXA) to reveal segmental lean mass data for each side of the lower body (LB) and total body (TB). Countermovement jump (CMJ) assessment was completed in the same session on a force plate (AMTI, ACP) collecting data at 1,000 Hz to produce data for jump height (JH), peak power (PP), and propulsive impulse (Imp). Asymmetry magnitudes were quantified with the Limb Symmetry Index (LSI) {(larger value − smaller value)/(1/2[sum of values]) ×100} or TB SI ((larger value—smaller value)/((sum of values)), representing asymmetry as a percentage. Association between lean mass asymmetry and CMJ performance variables were evaluated with Pearson's product-moment correlations or Spearman's rank correlations depending on data normality. Results: LB LSI data were normally distributed, while TB LSI data were not (Shapiro-Wilk p = 0.839 & p = 0.009 respectively). Associations are shown as scatter plots in Figure 1. Pearson's correlations revealed only trivial to small negative relationships between LB LSI and JH (r = −0.103), PP (r = −0.312), and Imp (r = −0.258). A Spearman's correlation coefficient revealed a similar trend with TB SI (r = −0.302). No correlations resulted in statistical significance. Conclusions: These results are somewhat consistent with the only other study examining lean mass asymmetry and jumping performance decrement (Bell et al., 2014), in that lean mass asymmetry does not fully explain the interaction between force production asymmetries and overall jumping performance. Specifically, data from the current investigation suggests that it can only explain a trivial amount of the variance (<10%). Additional aspects, such as neuromuscular control and strength, need to be considered to fully understand this interaction. Practical Application: Lean mass asymmetry should not be considered the primary cause of poor jumping performance or force production asymmetry. It is likely that variables such as neuromuscular control and strength play a much larger role in explaining force production and jumping performance.

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Figure 1.:
Lean mass asymmetry and jumping performance. Scatter plots of lean mass asymmetry of the lower or total body and jumping performance variables.

(18) Heel Height Does Not Alter Coordination Patterns During the Squat

B. Romer,1 and H. Lu2

1High Point University; and2Texas Tech University

Athletic footwear design is highly varied based on the type of intended activity, construction materials, and artistic additions. A common theme of many athletic shoes though is an elevated heel height due to the influence of running footwear design. Previous research has indicated that even moderate heel heights can lead to altered lumbopelvic-hip kinematics, muscle activity, and reduced lifting capacity. While much of the previous research has relied on discrete measures of biomechanical variables, the use of coordination variability, a continuous type of measure, may aid in better understanding potential neuromuscular differences throughout the motion as opposed to specific points in the movement (i.e., peak hip flexion). Purpose: The purpose of the present study was to examine the influence of elevated heel heights on lower extremity coordination variability patterns during the execution of a low and high-effort squat. A secondary purpose was to examine potential differences in lower extremity coordination variability patterns during the eccentric and concentric portions of the movement. Methods: Twenty (age = 22.3 ± 4.1 years) resistance trained subjects (males, n = 10; females, n = 10) took part in a randomized protocol of 3 repetitions at 25 and 75% of their 1RM barbell squat at a 0, 5, 10, or 15° incline. Subjects performed 3 successive repetitions per condition, with zero inter-repetition rest. Heel height was adjusted to the designated heel height through custom-made wooden-lifting platforms set to specific incline levels (0, 5, 10, and 15%). All subjects utilized a standard, zero-drop (e.g., flat) athletic shoe. Sagittal plane kinematics were collected through a single Basler Scout camera recording at 100 Hz and processed through MaxTRAQ2D. A custom Matlab program was utilized to determine the continuous relative phase (CRP) ratios and deviation phase (DP: coordination variability) of the thigh-shank during each condition. Separate repeated measures ANOVA's were completed to examine the influence of heel height (0, 5, 10, 15) on DP within a given %1RM. Secondary analysis was performed to examine the role of muscle actions during paired conditions (i.e., 25% of 1RM—0% Incline—Concentric, 25% of 1RM—0% Incline—Eccentric) Results: Results indicated no significant differences in the DP of the thigh-shank during any lifting grade at 25% or 75% of 1RM. Similarly, results also indicated that the type of muscle action did not have a significant effect on DP at any gradient; While not significant, results did approach significance during the 15% incline for both %1RM conditions. Conclusions: The results of the present study would tend to suggest that elevated heel heights have little to no significant effects on coordination variability during a barbell squat; however, rather than direct manipulation of the foot through a raising the heel of the foot, the present study utilized a flat shoe and adjusted the gradient of the ground. Practical Application: The present study suggests that variations in heel height, a common component when comparing various athlete footwear, has a negligible effect on barbell squat kinematics; however, the present study utilized a continuous variable for analysis rather than discrete points in the movement. Given results of past research, future research should examine the influence of muscular fatigue as the present study limited subjects to only 3 repetitions.

(19) Does 4-Weeks of Leg Press Training Influence Electromechanical Delay Measurements and Improve Performance?

J. Mendoza, O. Salmon, J. Jenkins, and C. Smith

University of Texas at El Paso

Purpose: The purpose of the study was to examine the differences in electromechanical delay (EMD) during step isometric muscle action following 4 weeks of dynamic constant external resistance (DCER) leg press training. Electromechanical delay can be further described as the onset of electromyographic signals to mechanomyographic signals (EMDE-M) the onset of mechanomyographic signals to force signals (EMDM-F), and the onset of electromyographic signals to for signals (EMDE-F). Methods: 12 recreationally trained males (age 21.4 ± 3.6 years; height 181.86 ± 10.23 cm; weight 81.3 ± 16.2 kg) underwent 4 weeks of DCER training which consisted of 3 sets of 10 repetition on leg press 3 days per week for the 4 weeks. If the individual was able to complete greater than 10 repetitions on their final set, the weight was increased by increments of 2.5 kg. The DCER training group performed step isometric muscle action testing (% of maximal voluntary isometric contraction (MVIC)) on the Cybex 6,000 isokinetic dynamometer leg extension at 20%, 40% 60, 80, and 100% of the individual's baseline MVIC. Each individual was tested at Week −0 (baseline), Week −2, and Week −4. Electromyography (EMG) sensors were placed bilaterally on the subject's vastus lateralis (VL) with mechanomyography (MMG) sensors placed between the EMG electrodes. EMG and MMG signals were sampled at 10 kHz. Force was monitored with a load cell mounted at the end of the of the lever arm between the shin pad and the Cybex 6,000. A knee joint angle of 120° (full extension at 180°) was used during all testing. Results: The DCER group showed no significant difference in the EMD: EMDE-M, EMDM-F, EMDE-F during Week −0, Week −2, and Week −4 at 20%, 40% 60, 80, and 100% MVIC repeated measures ANOVA (p = 0.111, ηp2 = 0.14). There was a significant two-way interaction for EMD by Intensity (p < 0.01, ηp2 = 0.61). The follow-up EMD by Intensity repeated measure ANOVA, collapsed across Visit and Leg, was significant (p < 0.01, ηp2 = 0.30). The follow-up one-way repeated measures ANOVA for EMD was significant (p < 0.01, ηp2 = 0.98) and indicated that EMDE-M < EMDM-F < EMDE-F (p < 0.01 for all comparisons). In addition, the follow-up one-way repeated measures ANOVA for Intensity was significant (p < 0.01, ηp2 = 0.30) and indicated that 20 = 40 > 60 > 80 = 100% MVIC. Conclusions: Four weeks of DCER leg press training did not produce any significant changes in EMDE-M, EMDM-F, EMDE-F. However, there was a significant decrease in EMDE-M, EMDM-F, EMDE-F with each incremental increase in isometric step muscle action intensity universally among the DCER training group. Decreases in EMDE-M were near proportional to decreases in EMDM-F as isometric step muscle action intensity was increased. Practical Applications: These results suggested that 4 weeks of DCER training is ineffective at decreasing EMD. Athletes looking to shorten reaction time through a decrease in EMD may look to other modes of training. The results also suggested that maximal effort is required to elicit the shortest EMD durations which indicates that athletes wanting to achieve a decrease in EMD must exert maximal force during training in order to exhibit the greatest performance.

(21) Associations Between Lower Limb Forces and Jab Punch Force in Elite Male Amateur Boxers

J. Pádecký,1 P. Kubový,1 J. Brich,2 R. Jebavý,1 and J. Tufano1

1Charles University; and2Technical University of Liberec

The most common boxing punch is the straight jab, which is assumed to be initiated by legs, followed by slight trunk rotation, shoulder flexion and elbow extension. However, to our best knowledge, there is no evidence supporting the association between lower limb force with jab force. Purpose: Therefore, the purpose of this study was to quantify lower limb forces and their association with jab peak force (PFJAB). Methods: Twelve elite male amateur boxers (80.4 ± 11.1 kg, 181.6 ± 7.1 cm, 8.0 ± 5.9 years of boxing experience) participated in this study, which took place over 2 laboratory visits: familiarization and experimental. During the experimental visit, subjects completed a general warm up followed by a boxing-specific warm up. After 4 minutes of rest, subjects performed 1 maximal effort jab while standing on 2 tri-axial force plates (Kistler group, Switzerland) in a self-selected stance. Subjects were instructed to punch the center of a separate tri-axial force plate that was suspended in the air at chin level (Kistler group, Switzerland). The sampling frequency of all force plates was set at 12,000 Hz. Synchronized video recordings were used to identify the start of the punch using Qualisys Motion Tracking Manager (QTM) with a sampling frequency of 500 fps. All forces were transformed into relative forces (Newtons of force per kilogram of body mass). Standard multiple regression was used for 2 models separately, which included rear leg peak forces (PFRL) in the ×, y, and z directions as independent variables for one model, and lead leg peak forces (PFLL) in the x, y, and z directions as independent variables for the second model, both with PFJAB as the dependent variable. Results: PFJAB was 0.81 ± 0.15 N·kg−1, PFRL in x, y and z direction (0.22 ± 0.09 N·kg−1, −0.07 ± 0.06 N·kg−1 and 0.86 ± 0.32 N·kg−1, respectively) and PFLL in x, y and z direction (−0.30 ± 0.27 N·kg−1, 0.19 ± 0.16 N·kg−1 and 0.81 ± 0.46 N·kg−1, respectively). Standard multiple regression model for PFRL resulted in R = 0.55, R2 = 0.30, and adjusted R2 = 0.04 with non-significant F change 0.38, while the model for PFLL resulted in R = 0.44, R2 = 0.19, and adjusted R2 = −0.10 with non-significant F change of 0.60. Standardized Beta coefficients, correlations, and collinearity statistics are present in Table 1. Conclusions: Leg force only explained only a small, insignificant variance in PFJAB, suggesting that other variables such as trunk rotation, arm extension, and effective mass may be larger contributors to PFJAB. The most explained variance from the dynamics of the legs may be with PFRL in the z and x directions. However, it should be noted that these fighters were well-trained boxers, and the contribution of the legs may differ between experience levels. Practical Application: Strength and conditioning specialists should implement a combination of upper body pushing, lower body lateral, and rotational exercises within a periodized training plan in order to increase PFJAB.

Table 1 - Coefficient statistics for peak jab force.
Beta—the contribution of the independent variable to peak jab force. Zero-Order—correlation between peak jab force and independent variable. Partial correlation—correlation between independent variable and peak jab force after the linear effects of other independent variables have been removed from both the independent and dependent variable. Part correlation—is the correlation between an independent and peak jab force after the linear effects of other independent variables have been removed from the independent variable. Tolerance—value greater than 0.10 is needed, VIF values less than 10 are needed.

(22) The Effect of an Acute Bout of Short Foot Exercise on Vertical Jump Height

T. Beggs, C. Owen, K. Knox, O. Nash, A. Arant, D. Johnson, R. Dudley, and A. Du Bois

Azusa Pacific University

Triple extension of the hip, knee and ankle joints is essential for vertical jump performance. Additionally, jump performance is moderately correlated with the rate of torque development and peak torque of the ankle joint. The midfoot is anatomically integral in supporting and stabilizing the ankle during push-off. When push-off demand increases, ankle and midfoot power increase proportionally. Chronic, long-term training of the midfoot has been shown to increase midfoot strength as well as vertical jump height. Purpose: Therefore, this study investigates whether acute short foot exercise training before jump performance has a positive effect on vertical jump height. It is hypothesized that vertical jump height will increase immediately following the short foot exercise. Methods: Ten right leg dominant subjects (6 males, 4 females; Age: 24.9 ± 1.91 years; Height: 1.71 ± 0.08 m; Mass: 66.09 ± 10.39 kg) performed acute short foot exercise in order to examine the impact on vertical jump height. Testing began with drop jumps (DJ) off an 18-inch box (PRE). Subjects were told to step off the box with their hands on their hips, land with feet on the force plate, and immediately jump as high as possible. Two familiarization trials were performed followed by 3 test trials, with one minute of rest between each DJ. Following the DJ trials, subjects performed 2 sets of 30 repetitions of short foot exercise on each foot while seated. Each contraction was held for 5 seconds with 2 seconds of rest between repetitions. During the exercise, subjects were told to imagine bringing the ball of their foot towards their heel without curling their toes. Two more sets were completed for each foot while standing. Immediately following the exercise, subjects performed 3 additional DJ (POST). The average jump height of 3 trials was used for data analysis. Means and SD were calculated for DJ height. The difference in PRE and POST DJ height was analyzed with a paired samples t-test. The a priori alpha (α) was set at 0.05. Results: DJ height significantly decreased (PRE: 44.3 ± 6.6 cm, POST: 42.1 ± 6.1 cm; p = 0.020, d = 0.89) after short foot exercise. Conclusions: Contrary to the hypothesis, vertical jump height of subjects after an acute bout of short foot exercise was impaired. This was likely due to fatigue of the intrinsic foot musculature. The intrinsic foot musculature absorbs forces during landing and assists the ankle in generating power for push-off. Therefore, the midfoot is integral for both landing and propulsion during a drop jump. Given the limited research on the acute effects of short foot exercise, the exercise protocol was based on short foot programming in chronic studies. Therefore, the volume of acute exercise may have been excessive, thus inducing muscle fatigue in the subjects. Future research must be conducted to find a more appropriate acute training volume for the midfoot. Practical Application: Based on the findings of this study, short foot exercise immediately prior to activities requiring absorption and propulsion could be detrimental to performance. While chronic studies support strengthening the intrinsic foot muscles in order to improve vertical jump height, this study suggests that exercise prior to performance has the opposite effect. Therefore, warm-up procedures for jumping activities should not include a high volume of short foot exercise.

(23) Relationships Between Hex Barbell One Repetition Maximum and Maximal Isometric Pulls at 3 Different Positions

B. Miller, E. Arroyo, E. Tagesen, and A. Jajtner

Kent State University

Purpose: To examine the relationships between hex barbell (HBB) deadlift one-repetition maximum (1RM) and force-time characteristics of maximal isometric pulls (IP) from the floor, knee, and mid-thigh positions. Methods: 23 healthy adults (men: n = 13, women: n = 10; 23 ± 4 years; 172.4 ± 9.7 cm; 75.3 ± 15.5 kg; HBB 1-RM: 132.1 ± 48.8 kg) completed an HBB deadlift 1RM assessment and a series of maximal IP on separate days. Bar heights for IP were set at 22.5 cm above the platform to represent the lift-off phase (FLOOR), just superior to the patella to represent the knee-passing phase (KNEE), and the mid-thigh—defined as the mid-point between the center of the patella and the anterior superior iliac spine (MT). Three 6-second maximal IP at each position were performed in a randomized order with 3 minutes of rest between trials. Data were averaged and analyzed for peak force (PF), time-specific force values at 50, 100, 150, 200, and 250 ms, and rate of force development (RFD) time-bands at 0–30, 0–50, 0–90, 0–100, 0–150, 0–200, and 0–250 ms. Pearson's Product Moment correlations were performed to assess the relationships present between 1RM and PF, time-specific force variables, and RFD time-bands at each position with significance set a priori at α ≤ 0.05. Effect sizes were interpreted as small (0.10–0.29), moderate (0.30–0.49), large (0.50–0.69), very large (0.70–0.89), and extremely large (0.90–1). Results: Correlation coefficients between 1RM and force-time characteristics at FLOOR presented a very large relationship to PF (r = 0.862, p ≤ 0.001), large to very large relationships to all time-specific force variables (r = 0.534–0.806; p ≤ 0.009), and moderate to very large relationships between all RFD time-bands (r = 0.451–0.743; p ≤ 0.031). Correlation coefficients between 1RM and force-time characteristics at KNEE presented a very large relationship with PF (r = 0.819; p ≤ 0.001), large to very large relationships to force-time specific variables (r = 0.651–0.754; p ≤ 0.001), and moderate to very large relationships to all RFD time-bands (r = 0.471–0.700; p ≤ 0.023). Correlation coefficients between 1RM and force-time characteristics at MT presented large relationships to PF (r = 0.690; p ≤ 0.001) and all time-specific force variables (r = 0.523–0.658; p ≤ 0.010), and moderate to large relationships to all RFD time-bands (r = 0.479–0.630; p ≤ 0.021). Conclusions: Results of this investigation demonstrated that the greatest relationships between 1RM and force-time characteristics were observed at the FLOOR position, while the weakest relationships were observed at the MT. PF presented the greatest relationship to 1RM at all 3 positions. RFD at 0–150, 0–200, and 0–250 ms, and force at 150, 200, and 250 ms presented the strongest relationships to 1RM in the FLOOR and MT positions, however the strongest relationships for the KNEE position were seen in RFD at 0–90, 0–100, and 0–150 ms, and force at 100 and 150 ms. Maximal strength has been related to late-phase RFD; thus, it is not surprising to observe greater relationships at later time epochs from the FLOOR and MT positions. It may be appropriate to perform IP from the lift-off position to better predict performance during a 1RM deadlift using an HBB. Practical Application: Strength and conditioning coaches should consider incorporating IP from the lift-off position to monitor training adaptations to the HBB deadlift, as it appears to be related to maximal strength better than the commonly performed isometric mid-thigh pull.

(24) Segmental Bioelectrical Impedance Spectroscopy to Assess Muscle Size and Quality in Normal Weight and Obese Older Men

L. Arieta,1 H. Giuliani,1 G. Gerstner,2 J. Mota,3 N. Shea,4 and E. Ryan1

1University of North Carolina at Chapel Hill;2Old Dominion University;3University of Alabama; and4Georgia Institute of Technology

Aging is accompanied by a progressive loss of muscle mass and increased infiltration of non-contractile tissues (e.g., intramuscular fat). Obesity in older adults has been shown to exacerbate declines in physical function, in part due to greater increases in intramuscular fat. It has been suggested that the electrical properties of segmental bioelectrical impedance spectroscopy (SBIS) can be used as a surrogate measure of muscle size and quality. Purpose: To assess if electrical properties of SBIS are reflective of differences in muscle size and quality in normal weight and obese older men. Methods: Twenty-two normal weight, healthy, older men (ON) (mean ± SD age: 69.4 ± 2.1 years; body fat: 24.4 ± 1.4%) and 19 age-matched obese older men (OB) (age: 69.1 ± 2.5 years; body fat: 36.7 ± 0.9%) visited the laboratory on one occasion. Prior to data collection, subjects refrained from vigorous exercise for 48 hours and fasted for a minimum of 8 hours. Body fat percentage (%BF) was assessed with a dual energy X-ray absorptiometry scan. Panoramic brightness mode ultrasound imaging was used to determine subcutaneous fat corrected echo intensity (EI) as a measure of muscle quality, as well as anatomical cross-sectional area (CSA) as a measure of muscle size. Following a twenty-minute lying rest period, each of the superficial quadriceps muscles (vastus lateralis, vastus medialis, and rectus femoris) were analyzed individually at 50% of femur length with the right knee supported at 50 degrees of flexion. The EI values were averaged across all 3 muscles and the CSA values were summed across all 3 muscles. A multi-frequency SBIS was used to measure resistance and reactance of the right thigh and the data was modeled in a Cole-Cole plot, from which characteristic frequency (CF) and phase angle (PA) were calculated. Independent samples t-tests and Cohen's d were used to determine group differences. Pearson's product-moment correlation coefficients were used to determine the association between EI and CSA with CF and PA. Results: Age was not different between groups (p = 0.669, d = −0.134). Body fat percentage, EI, CSA, CF, and PA were all significantly different between groups (p ≤ 0.001; See Table 1). Characteristic frequency had a significant negative correlation with CSA (r = −0.597, p < 0.001) but not with EI (p = 0.244). There was a significant negative correlation between PA and EI (r = −0.765, p < 0.001) but not with CSA (p = 0.469). Also, there was no relationship between CF and PA (p = 0.449). Conclusions: Higher CF values were related to a smaller CSA values, whereas a higher PA was related to lower EI values. Given CF and PA were not related, these findings may suggest that CF and PA are unique measures of muscle size and quality, respectively. Practical Application: Segmental bioelectrical impedance spectroscopy may serve as a cost effective, time efficient, and portable assessment to monitor muscle size and quality in older adults.

Table 1 -
Mean ± SD, p values from independent samples t-tests, and the Cohen's d effect size statistic for the demographic, ultrasound, and bioelectrical impedance spectroscopy values for the normal weight and obese older men.

(25) Biomechanical Comparison of the Bulgarian Split-Squat and Back Squat

E. Mackey, B. Riemann, and A. Flatt

Georgia Southern University

The principle of specificity suggests resistance exercises should closely resemble the mechanics and loads required to perform functional activities. Many sport skills rely on fundamental lower body movements performed in a unilateral fashion or contain transient periods of unilateral stance (e.g., running). The Bulgarian split squat (BSS) is a unilateral lower extremity strength exercise, however the mechanical demands have not been fully elucidated. Purpose: To compare ankle, knee, and hip joint kinetics and kinematics between the BSS and traditional bilateral back squat (BS). Methods: Twenty males (24.2 ± 2.5 yrs, 1.76 ± 0.06 m, 85.3 ± 13.9 kg) with >6 months lower extremity resistance training completed 2 days of study participation (48 hours separation). Following a progressive (i.e., unloaded to loaded barbell) BSS familiarization protocol, the BS one repetition maximum (1RM) was established for each subject. BSS technique involved the dominant foot placed anterior and in-line with hip joint while the rear foot was elevated patella height. Both the BSS and BS were performed to a 90° knee flexion depth. During the second session, 2 × 3 BS (70% 1RM) and BSS (35% 1RM) were completed (counterbalanced order) while three-dimensional kinematics and ground reaction forces were collected and used to quantify ankle (AN), knee (KN) and hip (HI) net joint extensor moment impulse (NJMI) and work. Additionally, concentric(CON)/eccentric(ECC) phase times and AN, KN, and HI peak angular displacement were computed. Results: Significant squat type × joint interactions were revealed for both NJMI (p < 0.001, ηp2 = 0.78) and work (p < 0.001, η2p = 0.61). For both squats, hip NJMI (Figure 1A) and work (Figure 1B) was significantly greater than both AN(d = 5.5–9.4) and KN (d = 7.5–8.5). While KN NJMI during the BSS was statistically less compared to AN (d = 2.8), during BS KN NJMI was statistically greater than AN (d = 3.0). AN and KN work were statistically similar during BSS (d = 0.3), whereas KN work was statistically greater than AN during BS (d = 3.2). For both BSS (p < 0.001, d = 1.6) and BS (p = 0.003, d = 1.1), the ECC phase was significantly longer than CON, however the CON for BSS was significantly shorter than BS (p = −17, d = 0.56). During the BSS, AN displacement was significantly less than KN (p < 0.001, d = 5.6), which in turn was significantly less than HI (p = 0.004, d = 0.62). In contrast, during BS, HI and KN displacement was statistically identical, with the AN being significantly less than both (p < 0.001, d = 7.3–7.5). Conclusions: Both the BSS and BS are HI dominant exercises. While the KN is secondarily involved with BS, the KN is less involved with the BSS. Practical Application: The BSS may be best selected in circumstances when the goal is to focus on HI extension while minimizing KN joint demands, such as early phases of KN rehabilitation.

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(26) Relationship Between Unilateral Force and Power Capabilities and Asymmetries in Jumping

W. Amonette, A. Anders, T. Chapman-Lopez, M. Choate, Z. Von Ruff, K. English, and J. De Witt

University of HoustonClear Lake

Purpose: To determine relationships between unilateral peak force, rate of force development, and power generating capabilities using an instrumented leg press and right and left leg kinetics during bilateral Static Squat Jumps (SSJ). Methods: Twenty-five women (24.9 ± 2.7 y; 168.4 ± 5.1 cm; 65.5 ± 5.0 kg) who were professional soccer players volunteered. They participated in one testing session during which peak isometric force (PF), rate of force development (RFD) and dynamic peak power (PP) were measured using a 45-degree, instrumented leg press. The leg press was equipped with extended rails, a force platform mounted to the footplate, a velocity transducer affixed perpendicular to the footplate, and a magnetic brake that eliminated eccentric loading. The athletes performed 3 repetitions of unilateral peak isometric presses with a knee angle of 90°; they were verbally encouraged to “push as hard and fast as possible.” From the same 90-degree knee flexion position, 3 sets of 3 repetitions of peak velocity unilateral throws were performed with a load of 50% of the measured isometric PF. After an ample rest, verbal instruction, and practice attempts, 3 repetitions of bilateral SSJ were performed with the right and left foot positioned on separate force platforms. The peak effort attempts were executed from the squatted position and athletes were encouraged to jump as high as possible. Instantaneous PF, RFD, and PP were computed for the right and left leg from isometric and dynamic leg presses. Instantaneous PP was also computed from the right and left force platforms during the SSJ. Pearson's r was determined from unilateral PF and RFD during leg presses and right and left leg power during SSJ. Difference scores were calculated between the right and left leg PP derived from the leg press throw tests and right and left leg PP during the bilateral SSJ. These data (mean ± SD) were compared using paired t-tests (p < 0.05). Results: Unilateral PF for the left and the right leg were 920.1 ± 29.3N and 929.7 ± 26.3N, respectively. PP generated during the SSJ by the left and right leg were poorly correlated to the measured isometric PF (Left; r = 0.06; Right; r = 0.15) and RFD (Left; r = 0.07; Right; r = 0.16). On average, athletes were more powerful with their left than right leg during unilateral leg press throws (Δ19.1 ± 15.9 W). However, they tended to push with more power with the right compared to left leg during SSJ (Δ17.7 ± 17 W), but these differences were not significant (p = 0.19). Nine of 26 athletes pushed with more power in the SSJ with the leg that measured less powerful in the leg press throw. Conclusions: These data indicate differences in raw strength and power capabilities of each leg may lead to asymmetries in jumping, but in some athletes, variances could be an adapted motor control strategy and not an imbalance needing correction with strength exercises. Practical Application: In this sample of women professional athletes, asymmetries observed in jumping were due to unilateral strength and power capabilities, in some but not all athletes. Measuring forces and power generated by the right and the left leg during SSJ is most appropriate for providing information describing changes within the athlete, for example after injury, recovery, or fatigue and not as a single point measure to quantify unilateral capabilities.

(27) Acute Endocrine and Hematological Responses to Rest Redistribution With Heavier Loads for the Squat Exercise

S. Moses, S. Chae, S. McMullen, C. Bailey, D. Hill, and J. Vingren

University of North Texas

When using the same resistance training load, rest redistribution (RR) that incorporates intra-set rest stimulates similar growth hormone, testosterone, and cortisol responses compared to a traditional set (TS) protocol. RR may allow for heavier loads during exercise. However, no study has directly compared RR combined with a heavier load to TS. Purpose: The purpose of this study was to investigate the effect of RR combined with heavier loads (RR + L) on the acute growth hormone (GH), testosterone (TT), cortisol (C), white blood cells (WBC), lymphocytes (LYM), monocytes (MONO), and granulocytes (GRAN) responses in resistance-trained men. Methods: 10 resistance-trained men (mean ± SD; 23.3 ± 4.6 years; 175.6 ± 6.3 cm; 77.7 ± 10.8 kg; 4 ± 3 years training) completed 3 sessions each of which were separated by at least 3 days. One-repetition maximum (1RM) back squat (BS) (138.7 ± 30.2 kg) and 1RM BS:body mass (1.8 ± 0.2) were determined in Session 1. For Session 2 and 3, subjects were randomly assigned to either RR + L (4 sets of (2 × 5 reps) with 30 seconds (s) intra-set rest and 90 seconds inter-set rest using 75% 1RM BS) or TS (4 sets of 10 reps with 120 seconds inter-set rest using 70% 1RM BS). Subjects were instructed to perform every repetition “as explosively as possible.” Blood samples were collected before exercise (PRE), immediate post exercise (IP), and 5 (+5), 15 (+15), and 30 minutes post exercise (+30). Serum growth hormone, testosterone, and cortisol concentrations were determined using ELISA. WBC, LYM, MONO, and GRAN concentrations were determined with a CBC hemoanalyzer. Data were analyzed using two-way ANOVAs with repeated measures. Results: No effect of condition was observed; thus, results are reported across groups. A main effect of time point (p< 0.05) was observed for GH, TT, C, WBC, LYM, MID, and GRAN. Concentration of GH was greater at IP (58.28 ± 12.66 µIU/ml), +5 (62.78 ± 12.65), +15 (67.85 ± 13.26), and +30 (52.81 ± 11.22) compared to PRE (3.63 ± 1.59). TT was greater at IP (8.83 ± 1.09 ng/ml) and +5 (8.95 ± 1.13) compared to PRE (7.05 ± 0.75). C was greater at +15 (25.51 ± 2.91 µg/dl) compared to PRE (19.97 ± 2.73). Concentration of WBC was greater at IP (9.4 ± 0.6 103·µl−1), +5 (8.6 ± 0.7), +15 (7.2 ± 0.7) compared to PRE (5.2 ± 0.4). LYM was greater at IP (3.8 ± 0.3 103·µl−1) and +5 (3.3 ± 0.3) compared to PRE (1.7 ± 0.1). MONO was greater at IP (0.8 ± 0.1 103·µl−1) and +5 (0.7 ± 0.1) compared to PRE (0.4 ± 0.0). GRAN was greater at IP (4.9 ± 0.6 103·µl−1), +5 (4.6 ± 0.6), +15 (4.1 ± 0.6) compared to PRE (3.2 ± 0.4). Conclusions: RR + L resulted in similar responses compared to TS for TT, GH, C, WBC, LYM, MID, and GRAN. Practical Applications: Practitioners may incorporate RR + L without detrimental effects on the acute endocrine response.

(28) Assessments of Serum and Metabolic Biomarkers Along With Performance Level Over the Course of a Collegiate Cross Country Season

D. Hooper,1 T. Carlson,2 J. Vingren,3 B. Riemann,4 and R. LeFavi5

1Jacksonville University;2Georgia Southern University Armstrong;3University of North Texas;4Georgia Southern University; and5University of South Carolina at Beaufort

Reduced serum testosterone (T) concentration has been frequently used as a potential indicator of overreaching or overtraining. While reduced T has been demonstrated during periods of high training intensity or volume, and particularly in endurance athletes, it is not always associated with a reduction in performance level. Purpose: The purpose of this study was to assess changes in serum T, in addition to other markers of overreaching and overtraining, in combination with performance measures over the course of a collegiate cross country season. Methods: 9 male collegiate (NCAA Division I and II, NAIA Division I) cross country runners (height: 182 ± 6 cm; weight: 70.9 ± 6.4 kg) were assessed at the mid-point of the competitive season (MID), immediately following post-season events (POST) and once more during the off-season (OFF). At each time point, 10 ml of blood was collected from an antecubital vein and later analyzed for serum testosterone (T), insulin-like growth factor (IGF), vitamin D (Vit D) and interleukin-6 (IL6). Resting metabolic rate (RMR), maximal oxygen consumption (V̇o2max) and running economy (RE) were measuring using indirect calorimetry. Measured RMR was compared to predicted RMR (using Mifflin-St Jeor equation) to produce a measured RMR to predicted RMR ratio (RMR Ratio). Results: A repeated measures ANOVA determined that T (p< 0.001), IL6 (p < 0.05) and V̇o2max (p < 0.05) differed significantly across the 3 time points. T increased significantly (p < 0.001) from MID to POST (MID: 14.2 ± 3.0 vs. POST: 16.2 ± 2.7 nmol/L) and remained significantly above MID at OFF (POST: 16.2 ± 2.7 vs. OFF: 16.7 ± 1.8 nmol/L). IL6 significantly (p < 0.05) increased from POST to OFF (POST: 18.8 ± 4.2 vs. OFF: 21.5 ± 5.6 pg/ml). V̇o2max significantly (p < 0.05) increased from MID to POST (MID: 64.5 ± 4.5 vs. POST: 68.1 ± 3.4 ml/kg/min) and significantly (p < 0.001) reduced from POST to OFF (POST: 68.1 ± 3.4 vs. OFF: 62.5 ± 4.2 ml/kg/min). No other significant differences were observed. Conclusions: The majority of the serum T concentrations of these athletes were lower than typically seen in non-athletes. However, despite the very high volumes of running that these athletes were undertaking, serum T did not decrease and in fact, increased over the course of the season and remained elevated following the off season. When compared to changes in performance, increases in T did correspond with increases in V̇o2max from MID to OFF, but differed when V̇o2max decreased from OFF to POST but T did not, despite an elevation in IL6. Practical Application: Serum T has consistently been used as a potential indicator of overreaching and overtraining. However, this study adds to prior recent research that shows that serum T does not always correspond to performance level and thus is likely not a useful marker of overreaching or overtraining by itself.

(29) Evaluation of Salivary Alpha Amylase as a Measure of Sympathetic-Adreno-Medullar Axis Activity at Rest

D. Bellar,1 and L. Judge2

1University of North Carolina at Charlotte; and2Ball State University

Purpose: The sympathetic-adreno-medullar axis (SAM) is associated with blood pressure, heart rate, and other hemodynamic variables. The SAM axis is also implicated in overtraining syndrome, where athletes have elevated resting heart rate and blood pressure and lack the ability to adequately recovery between sets or bouts of training. The present investigation was designed to evaluate the utility of Salivary Alpha-Amylase in monitoring resting SAM axis activity and its association with hemodynamic variables. Methods: Twelve healthy young adults (male = 3, female = 9, Age = 22.6 ± 4.5) volunteered for the present investigation. The volunteers reported to the lab on 3 separate occasions at similar times of day and provided a saliva sample and a five-minute recording using a non-invasive finger cuff blood pressure system. The saliva samples were analyzed for Alpha-Amylase (AA) and Cortisol (CORT) using commercially available kinetic and Elisa assays respectively. Intersession variation in AA and CORT were assessed with one-way ANOVA. Hemodynamic variables were compared to salivary measures using Pearson's correlations. Results: Salivary AA corrected for flow rate was not found to significantly vary between measurement days (F = 0.642, p = 0.533). Salivary CORT was similarly not found to vary between measurement days (F = 0.834, p = 0.443). AA was not found to be correlated with mean arterial pressure (r2 = 0.03, p = 0.32), heart rate (r2 = 0.03, p = 0.35), pulse pressure (r2 = 0.06, p = 0.15), pRR50(5) (r2 < 0.01, p = 0.93), or inter-beat interval (r2 = 0.07, p = 0.12). CORT was found to be significantly correlated to both heart rate (r2 = 0.14, p = 0.03) and inter-beat interval (r2 = 0.15, p = 0.02). CORT was not associated with any other hemodynamic variables. Conclusions: Salivary alpha-amylase appears to be a stable measure across trials. However, it does not appear to be associated with hemodynamic variables. CORT measured at similar times of day in saliva similarly appears to be a stable measure. It is weakly associated with heart rate and inter-beat interval. Practical Application: For practitioners and researchers having reliable measures of the SAM axis that are non-invasive, reliable and that allow for sample collection in the field are important. Assessment of SAM axis is important to understand if athletes are at risk for overtraining syndrome. However, based upon the results of this study, it does not appear that Salivary Alpha-Amylase should be considered for assessment of overtraining syndrome in athletes.

(30) The Effects of a Semester of Vocational Dance Training on Biomarkers and Performance Variables in Elite Adolescent Ballet Dancers

D. Sanders,1 M. Murray,1 B. McFadden,2 A. Walker,3 B. Bozzini,4 H. Cintineo,2 M. Bello,5 A. Chandler,2 M. Arent,2 and S. Arent2

1Rutgers University;2University of South Carolina;3Lebanon Valley College;4University of South Carolina Sport Science Lab; Rutgers, The State University of New Jersey; and5Mississippi State University

Energy expenditure (EE), performance and biomarker assessments are popular in athletics as they provide a comprehensive approach to athlete monitoring in order to optimize health and performance. Currently, research in elite, adolescent artistic-athletes (e.g., dancers) is limited, especially in regard to biomarkers. Purpose: To evaluate changes in performance and biomarker variables over the course of a semester in elite male and female adolescent ballet dancers and to compare differences between sexes. Methods: Male (n = 10; Mage = 16.8 ± 1.6 years; Mheight = 173.7 ± 7.8 cm) and female (n = 14; Mage = 15.4 ± 1.3 years; Mheight = 162.8 ± 6.3 cm) ballet dancers were recruited from a vocational ballet school. Performance testing occurred at the beginning and end of semester and included measurement of body weight (BW), body fat percentage (%BF), lean body mass (LBM), vertical jump height (VJ), vertical jump power (VJW), and a maximal graded exercise test to assess V̇o2max and ventilatory threshold (%VT) via indirect calorimetry. Menstrual status was assessed in females pre- and post-study via questionnaire. Biomarkers were collected at the beginning of the semester (T1) and every subsequent 4-weeks (T2-T5). Athletes reported for blood draws ≥12 hours rested, fasted, and euhydrated between 07:00 and 09:00 h. Thyroid-stimulating hormone (TSH), free and total triiodothyronine (T3F, T3T), free and total thyroxine (T4F, T4T), free and total cortisol (CORTF, CORTT), free and total testosterone (TESTF, TESTT), estradiol (E2), follicular-stimulating hormone (FSH), growth hormone (GH), insulin-like growth factor-1 (IGF1), TNF-α, vitamin d, 25-OH (Vit-D), iron (Fe), iron binding capacity (IBC), and percent saturation (%Sat) were assessed. Total (TEE) and exercise (EEE) energy expenditure were collected over a typical 7-day training epoch using a Polar M430 watch and H10 monitor. ANOVAs and RM-MANOVAs were used to identify differences between male and female dancers, and univariate follow-ups were used to find changes over time with significance set at p< 0.05. Cohen's d was calculated to determine with-in sex magnitude of change. Results: Significant sex by time interactions were found for CORTF and FSH (p < 0.05). Significant sex differences were found in EEE, TEE, BW, %BF, VJ, VJW, V̇o2max, T3F, TESTF, TESTT, E2, FSH, GH, and %Sat (p < 0.05). Time main effects were found for BW, VJ, VJW, TSH, T3T, T4F, CORTF, CORTT, TESTT, FSH, TNF-α, Vit-D, Fe, and %Sat (p< 0.05). In females, significant alterations in TSH, T4F, CORTT, TESTF, TESTT, FSH, IGF-1, TNF-α, Vit-D, Fe, and %Sat were found (p< 0.05). No changes in E2 were found, but cases of amenorrhea increased. In males, significant alterations in T3T, CORTT, CORTF, TESTT, FSH, TNF-α, Vit-D, and %Sat were found (p< 0.05). Conclusions: Biomarkers of iron status demonstrated adverse changes in females only. Further, HPG-axis disruption is apparent in females, but not males. Adolescent male and female ballet dancers showed similar EE when BW and LBM are taken into account. Sex differences were observed in performance variables, and VJ height in males (ES = 0.68) had a increase than females (ES = 0.10). Practical Application: Biomarkers, in conjunction with EE and performance testing, can be used to detect disruptions that may be negatively effect health and performance. Further, monitoring can be used to individualize interventions to the artistic-athlete's specific needs in order to optimize health and performance.

(31) Blood Flow Restriction During High Intensity Resistance Exercise Increases Inflammatory Response While Decreasing Muscular Performance

A. Fleming,1 C. Holmes,2 M. Jones,1 B. Hornikel,1 K. Saffold,1 M. Esco,1 and L. Winchester1

1The University of Alabama; and2Washing University School of Medicine

Ideal resistance training loads for inducing hypertrophy in skeletal muscle are >65% of 1 repetition maximum (1RM), with lighter loads having smaller effects on muscle growth. Blood flow restriction (BFR) devices, when used with light load resistance training, can result in skeletal muscle hypertrophy similar to that seen at higher loads with no BFR. High load resistance training and BFR training at low loads both promote protein synthesis and growth but through different cell signaling mechanisms. So, it could be plausible that co-activation of these pathways would result in a synergistic effect for added growth development. Localized application of ice over a given muscle group also decreases blood flow and may stimulate protein synthesis with resistance exercise similar to BFR. Purpose: The purpose of this study was to determine if BFR or ice application during an acute bout of heavy resistance exercise has an impact on muscle performance and muscular adaptations. Methods: Eleven healthy, resistance-trained individuals (age: 24.4 ± 5.4 years; ht: 176.0 ± 10.4 cm; wt: 80.7 ± 13.4 kg, and body fat: 18.2 ± 6.5%) participated in this study. Two 10 ml venous blood draws were taken during each experimental trial, one baseline to serve as a reference point and one 1-hour post-exercise to determine the change in Interleukin 6 (IL-6) and Vascular Endothelial Growth Factor (VEGF). Subjects performed 5 sets of 5 maximal knee extension and flexion against an isokinetic dynamometer. Exercise sessions occurred under 3 conditions: Control (CTL, no modifications), Ice (ICE, 2 gel icepacks wrapped around the thigh, to reflect the coverage associated with the BFR cuff) and BFR (cuff at 80% of personal occlusion pressure). Blood plasma was isolated and analyzed via enzyme-linked immunosorbent assay (ELISA) for changes in concentration of IL-6 and VEGF. Repeated measures ANOVAs were used with Bonferroni correction to determine if peak torque (%MVMC), IL-6, and VEGF values were significantly different between the 3 conditions (CTL, ICE, BFR). Pearson's correlations were used to determine relationships between all variables. A priori statistical significance was set to a value of p< 0.05. Results: Statistically significant mean differences were observed for %MVMC for flexion in the right leg for CTL vs BFR, p = 0.006 and ICE vs BFR, p = 0.021. Significant mean differences were also seen for the %MVMV for flexion in the left leg for CLT vs. BFR, p = 0.002, and ICE vs BFR, p = 0.003. Non-significant mean differences were observed between all other trial comparisons of %MVMC (all p > 0.05). Significant mean differences between BFR and CTL trials for IL-6, p = 0.049, respectively. Non-significant mean differences for all other trial comparisons of IL-6 (all p > 0.05). Non-significant mean differences for VEGF between all trial comparisons (all p > 0.05). There was a significant inverse correlation between VEGF and %MVMC for flexion between trials (r = −0.68, p = 0.045). There was also a significant direct correlation between dominant leg % MVMC flexion and extension between trials (r = 0.58, p = 0.003). Conclusions: Data reveals that IL-6 increases while maximal force production decreases when BFR is applied to the lower limb during high-intensity knee flexion. Practical Application: Results suggest that BFR in conjunction with high-intensity resistance training may provide greater hypertrophic response than traditional high-intensity training alone.

(32) Lack of Differences in Between Males and Females Post Exercise-Induced Muscle Damage

D. Wilburn, T. Cardaci, S. Machek, and D. Willoughby

Baylor University

Purpose: The purpose of this study was to exam the differences in the ubiquitin proteasomal system activation between genders in response to an eccentrically-biased muscle damaging aerobic bout of exercise. Methods: Twelve recreationally active male (6) and female (6) subjects between the ages of 18–30 were selected for this study. Subjects performed a 45 minutes eccentrically-biased muscle damaging treadmill protocol at 60% V̇o2max. Muscle biopsies and delayed onset muscle soreness (DOMS) analyses were performed 30 minutes prior and 3, 24, 48, and 72 hours following exercise-induced muscle damage. Skeletal muscle ubiquitin, MAFbx/Atrogin-1, ubiquitin specific peptidase 19 (USP19), and chymotrypsin-like protease concentrations were measured using ELISA. Two-way mixed model ANOVAs with pairwise comparisons were conducted with significance set at p ≤ 0.05 for comparisons. Results: There not a significant main effect between males and females (0.0006 ± 0.0002) on chymotrypsin concentration in muscle (p = 0.175). There was not a time by gender interaction on chymotrypsin (p = 0.66). There was a main effect for time (p = 0.033) showing an increase in chymotrypsin between the 48 hours (0.0006 ± 0.0002) and 72 hours (0.0009 ± 0.0002) only (p = 0.021). There was no time effect (p = 0.399) or gender by time interaction effect for MAFbx (p = 0.728). MAFbx in females (0.0056 ± 0.002) was elevated compared to men (0.0036 ± 0.001) but was not significantly different (p = 0.057). There was not a significant main effect for time (p = 0.608) or a time by gender interaction for ubiquitin concentration (p = 0.522). There was not a significant difference between males (0.0022 ± 0.0007) and females (0.0022 ± 0.0006) on ubiquitin concentrations in muscle (p = 0.826). There was not a main effect for time (p = 0.38) or a gender by time interaction on USP19 (p = 0.806). There was not a main effect between males (0.00003 ± 0.00001) and females (0.00003 ± 0.00001) on USP19 (p = 0.77). There was not a significant main effect between male (3.8 ± 2.5) and female (2.1 ± 3.5) DOMS measures (p = 0.958). There was not a significant interaction between gender and DOMs (p = 0.455). There was a main effect for time on DOMS (p< 0.001). Pairwise comparisons indicated increases in DOMS between 30 minutes prior and 24 hours post (p = 0.003), 30 minutes prior and 48 hours (p = 0.036) and decreases from 24 hours to 72 hours (p = 0.009), and 48 hours–72 hours (p = 0.012). DISCUSSION: Our findings show no significant differences in the ubiquitin proteasomal system activation between genders in response to damaging aerobic exercise. DOMS peaked 24 hours post and then continued to decline up to 72 hours post exercise and was not different between males and females. Despite the increase in DOMS, there was not significant gender or time differences across the several variables analyzed. Chymotrypsin concentration was elevated between 48 hours and 72 hours showing proteolysis is extended up to 3 days post-exercise. This shows that DOMS may be alleviated by the third day; however, remodeling may still be occurring during this time period an is not different between genders. Practical Application: This study provides insights into ubiquitin proteasomal system activity between genders post muscle damage. While more research is needed this data suggests males and females may not require separate recovery time frames after damaging eccentric aerobic exercise.

(33) The Effects of Whole-Body Photobiomodulation Light-Bed Therapy on Creatine Kinase and Salivary Interleukin-6 in a Sample of Trained Males: a Randomized, Crossover Study

J. Ghigiarelli, A. Fulop, A. Burke, A. Ferrara, K. Sell, A. Gonzalez, L. Pelton, J. Zimmerman, S. Coke, and D. Marshall

Hofstra University

Photobiomodulation therapy (PBMT) can be applied to the whole body as compared to the application of using single hand-held devices that isolate a smaller muscle area. Evidence is still lacking on examining high powered devices, using larger muscle groups, testing biochemical markers, and sampling athletic populations. Purpose: The purpose of this study was to examine the effects of an acute dose of whole-body PBMT pre- and post-high-intensity resistance training on creatine kinase (CK) and salivary interleukin-6 (IL-6) in a sample of trained males. Methods: Twelve males (31 ± 8.3 years, 177.2 ± 5.4 cm, and 86.0 ± 7.5 kg) were part of a randomized, counterbalanced, cross-over design, whereby each subject performed a high-intensity resistance training session that consisted of the bench press, chin-up, and repeated sprints on 2 separate occasions. Each subject was assigned to either the PBMT or control condition on 2 separate weeks, with a 10-day washout period between the weeks. Creatine kinase was measured at baseline, 24 hours (hrs), 48 hours, and 72 hours post-exercise. Interleukin-6 was measured at baseline, 60 minutes (min), 90 minutes, and 120 minutes. Results: A paired t-test showed no significant difference (p = 0.669) in the area under the curve (AUC) for CK during the PBMT (191.7 ± 48.3) and control conditions (200.2 ± 68.0). A Wilcoxon signed-rank test also showed no significant median difference (p = 0.155) in the AUC for IL-6 during the PBMT (Mdn = 347.7) and control conditions (Mdn = 305.8). An additional Wilcoxon signed-rank test for CK percentage change from 24hours to 72 hours showed the PBMT condition (Mdn = −45%) to have a non-significant −18% median difference as compared to control (Mdn = −41%), producing a moderate effect size (p = 0.071, r = −0.38). Conclusions: The current study, albeit lacking statistically significant findings for salivary IL-6 levels, did find a moderate effect for decreasing CK activity through the use of whole-body bed PBMT at a dose of 15 minutes immediately before and after high-intensity resistance training, comparable to the control treatment. Practical Application: The practical application is PBMT is a possible strategy to implement during periods of recovery from high-intensity resistance training.

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Figure 1.:
Creatine kinase concentration across baseline, 24, 48, and 72 hours.

(34) Endocrine and Body Composition Changes Across a Season in Collegiate Strength-Power Track and Field Athletes

G. Mangine,1 M. Stratton,2 A. Eggerth,1 J. Gough,1 Y. Feito,1 and T. VanDusseldorp1

1Kennesaw State University; and2Texas Tech University

Over 6–7 months, collegiate track and field athletes engage in resistance and event-specific training, in addition to several competitive events that culminate in the indoor (IC) and then outdoor National Championships (OC). For strength-power athletes (e.g., sprinters, jumpers, and throwers), perturbations in circulating concentrations of resting testosterone (T) and cortisol (C) may reflect their anabolic status and the accumulated stress of training and competition. Reduced T and elevated C may negatively impact lean mass and thus, performance in these athletes. Purpose: To monitor changes in T, C, and body composition in strength-power track athletes across their entire season. Methods: Nine female (20.3 ± 1.2 years, 169 ± 5 cm, 67.6 ± 8.5 kg) and 7 male (21.1 ± 2.0 years, 181 ± 9 cm, 77.3 ± 5.9 kg) Division I strength-power track athletes reported to the Human Performance Laboratory to provide fasted (8 hours) and resting (upon waking and having refrained from exercise for 24 hours) blood samples prior to the season (baseline), prior to and upon returning from IC, at the beginning and end of a heavy (HVY) mid-season training week, and prior to leaving for OC. Body composition was also assessed at baseline and prior to IC, HVY, and OC using a 4-compartment model (bioelectrical impedance analysis, air-displacement plethysmography [ADP], and dual-energy X-ray absorptiometry). The athletes were asked to complete a 24-hour dietary recall at baseline and repeat the same diet prior to all subsequent visits. Results: Linear mixed models with repeated measures indicated a sex × time interaction for T (p < 0.001) where men, who possessed higher concentrations overall, experienced a 20% reduction (p = 0.030) from IC to the onset of HVY and then a 50% improvement (p = 0002) after HVY; no changes were seen for women. Overall, concentrations in C were higher in women (p = 0.002) while the T-C ratio was higher in men (p < 0.001), and these were consistent across time. Main time effects (p < 0.001) were noted for body fat percentage, fat mass, and fat-free mass, where these measures remained consistent through IC before changing. Compared to baseline, fat-free mass increased by 2.74% by HVY (p = 0.023) but was then reduced by 3.81% prior to OC (p = 0.022). Compared to IC and HVY, body fat mass and percentage were elevated by 1.40–1.98 kg (p < 0.05) and 2.1–2.9% (p ≤ 0.007), respectively, whereas fat-free mass was down by 3.0–4.3 kg (p ≤ 0.003) at OC for all athletes. Though men generally possessed a lower body fat percentage (p = 0.025) and greater fat-free mass (p < 0.001), no sex × time interactions were observed for these measures. Conclusions: Resting concentrations of hormones indicative of anabolic status remained relatively consistent over the course of an entire season in strength-power track athletes. Perturbations in T were noted surrounding a heavy mid-season training period, specifically in men. Although changes in fat-free mass were also seen before and after this period, they occurred in all athletes; not just men. It is not clear if changes in T influenced the changes in fat-free mass surrounding the heavy mid-season training period. Practical Applications: For strength-power track athletes, maintaining a favorable resting T-C ratio, as well as maintaining or increasing fat-free mass, could reflect a positive anabolic response to the seasonal demands of training and competition, and be important for performance.

(36) Efficacy of Wearable Technology at Quantifying Power and Total Work of Endurance Runners Against Varying Wind Resistance

M. Bello, P. Williamson, F. Price, B. Shepherd, and J. Smith

Mississippi State University

Wearable technology has increased in popularity due to live feedback allowing training session adjustment in real time. In addition to HR monitoring, measuring power and total work may supplement other performance metrics and demonstrate differences in physical measures for training sessions with similar physiological stress. Purpose: The purpose of this study was to examine the efficacy of wearable technology at determining power and total work of endurance runners while running against varying levels of wind resistance. Methods: Eight trained endurance runners (5 females, 3 males) were recruited for this study and were currently running at least 120 min·wk−1 for the past 3 months. Subjects completed 3 sessions: 1 preliminary and 2 testing. All sessions were performed at least 2 hours fasted, at the same time of day, and subjects were asked to follow the same dietary intake prior to each session. Preliminary testing included screening and a V̇o2peak protocol. Subjects then completed 2 testing sessions in randomized order: one with no wind resistance (W0), and one with a wind resistance of 10 mph (W10). Each session involved a 20-minute run at 70% V̇o2peak. Power and total work were calculated using a power meter, HR was monitored via HR monitor, and RER, V̇o2 were monitored using a metabolic cart. The middle 10 minutes were analyzed for session means to avoid non steady state measures associated with beginning exercise and anticipation of completion. Paired t-tests were used to compare differences between sessions for all variables. Significance was set at p < 0.05. Results: There were no significant differences between RER, HR, or V̇o2 (p > 0.294) between sessions. There was a significant difference for power, with higher values in W10 compared to W0 (378.2 ± 45.2 vs. 364.5 ± 43.9 W; p = 0.001) There was also a significant difference for total work, with a higher work output in W10 compared to W0 (226.9 ± 27.1 vs. 218.7 ± 26.3 kJ; p = 0.001). Conclusions: The lack of significance in RER, HR, and V̇o2 demonstrates these runners sustained a similar physiological response for both testing sessions. However, the addition of wind resistance caused a significant increase in power and work output assessed by wearable technology in these endurance runners. These data indicate differences in physical performance in combination with the similar physiological response reflects the efficacy in the power meter for quantifying power and total work. Practical Applications: The use of a power meter to provide live feedback during training may be beneficial in assessing overall training stress. The differences seen in power and total work between testing sessions indicates the potential of the technology to assess physical changes. Further, the accumulation of differences in workload over time may result in a more robust physiological response. Therefore, the use of a power meter should be used in conjunction with HR monitoring.

(37) Comparison of the Critical V̇o2 to Ventilatory Thresholds and Critical Power

P. Succi, T. Dinyer, M. Byrd, E. Soucie, C. Voskuil, and H. Bergstrom

University of Kentucky

Fatigue thresholds, such as the ventilatory threshold (VT), critical power (CP), and the respiratory compensation point (RCP) demarcate the moderate, heavy, and severe exercise intensity domains. Specifically, the VT demarcates the moderate from heavy intensity domains, while CP represents the highest power output that can be sustained for an extended period of time without fatigue, and demarcates the heavy from severe exercise intensity domains. The RCP has been shown to occur at a similar relative intensity as CP. Furthermore, the CP model can be applied to physiological parameters such as V̇o2 to derive the critical V̇o2 (CVO2), which represents the highest metabolic intensity that can be sustained for an extended period of time without fatigue. The CVO2 is an individually derived threshold that may be used to examine issues related to endurance performance, such as the V̇o2 slow component. However, it is first important to determine where the CVO2 is located relative to the exercise intensity domains. Purpose: This study compared the CVO2 to the metabolic intensity (V̇o2) associated with critical power (VO2CP), VT, and RCP. Methods: Seven men and 3 women (mean ± SD, age 23 ± 4 years, height 178 ± 7 cm, weight 72 ± 10 kg) completed a graded exercise test to exhaustion (GXT) to determine V̇o2peak (47.62 ± 6.30 ml·kg−1·× min−1) and the power at V̇o2peak (pVO2peak). The VT and RCP were determined using the V-slope method from the VE vs. V̇o2, and VE vs. V̇CO2 plots, respectively. The CVO2 and CP were determined from the linear regression of the total oxygen consumed vs. time to exhaustion (TLim) and the total work vs. TLim, respectively, from 4 constant power output trials to exhaustion at 85–100% of pVO2peak. The VO2CP was determined from the V̇o2 vs. power output relationship from the GXT. Statistical analyses included a one-way repeated measures ANOVA (p < 0.05) with post-hoc Bonferroni corrected pairwise comparisons. The relationships among the VT, RCP, CVO2, and VO2CP were examined using zero-order Pearson product-moment correlations. Results: There was no difference (p = 0.115) between CVO2 (40.61 ± 5.56 ml·kg−1·min−1; 86% V̇o2peak) and RCP (36.37 ± 4.40 ml·kg−1·min−1; 77% V̇o2peak), but the VT (30.03 ± 5.02 ml·kg−1·min−1; 63% V̇o2peak; p < 0.001) and VO2CP (34.15 ± 5.70 ml·kg−1·min−1; 72% V̇o2peak; p < 0.001) were lower than CVO2. The VO2CP was not different from the VT (p = 0.190) or RCP (p = 0.620), but the VT was less than the RCP (p = 0.004). Additionally, the CVO2 was related to the VO2CP (r = 0.916), but not the VT (r = 0.594) or RCP (r = 0.573). The RCP was related to the VT (r = 0.665) and VO2CP (r = 0.735). Conclusions: The CVO2 represented an initial metabolic intensity that was higher than VO2CP and VT, but was not different from the RCP. Therefore, CVO2 was located at the upper end of the heavy or the lower end of the severe intensity domain, whereas VO2CP was located in the heavy intensity domain. The higher initial metabolic intensity of the CVO2 compared to the VO2CP may be related to the greater sustainability of exercise anchored by V̇o2 due to the alterations in power output to maintain a constant metabolic cost and control the V̇o2 slow component. Practical Applications: The CVO2 is an individually derived performance threshold that may have a number of applications including the prediction of endurance performance and the examination of issues related to the V̇o2 slow component phenomenon.

(38) Physiological Responses to Submaximal Cycle Ergometry With and Without a Fan

S. Truax,1 A. Fernandez,1 M. Culver,2 G. Wimer,1 and G. Grosicki2

1Georgia Southern University—Armstrong Campus; and2Georgia Southern University

The effects of convective (i.e., fan) cooling are often ignored in laboratory or indoor environments where exercise testing and training are frequently performed. Purpose: We sought to comprehensively compare physiological responses to submaximal, moderate-high intensity cycle ergometry with and without a fan. Methods: A total of 16 recreationally active young adults, including 8 women (age = 25.0 ± 4.3 years, body fat = 23.0 ± 6.0%, aerobic power = 36.1 ± 6.6 ml·kg−1·min−1) and 8 men (age = 24.1 ± 3.5 years, body fat = 12.5 ± 4.9%, aerobic power = 44.1 ± 12.3 ml·kg−1·min−1) participated in the study. After an initial visit to assess cardiorespiratory fitness, each subject performed two 40-minute training sessions on a cycle ergometer either with or without a fan (∼13 km·h−1), the order of which was randomized, while workload was continually adjusted to elicit 70% of heart rate reserve. Workload, oxygen cost, and respiratory exchange ratio were monitored throughout the test, and rating of perceived exertion (RPE) and perceived thermal sensation were recorded every 5-minute. Total energy expenditure of each training session was estimated via a computerized program interfaced with the cycle ergometer. Blood lactate was recorded before, halfway through, and immediately following each training session, and nude body mass was obtained pre-post. Results: Greater (p < 0.01) mean workload (+15%) and oxygen consumption (+9%) yielded significantly greater (p < 0.01) energy expenditure with fan cooling (344 ± 124 kcals) compared to without (302 ± 103 kcals). Perceived thermal sensation, but not RPE, was lower (p < 0.01) with fan cooling (3.8 ± 0.7) compared to without (5.5 ± 0.8), and body mass loss was attenuated (p < 0.05) with fan cooling (−0.4 ± 0.2 kg) compared to the non-fan trial (−0.6 ± 0.3 kg). Significantly higher (p < 0.05) blood lactate values were observed mid- (4.3 ± 1.9 vs. 3.4 ± 1.4 mmol·L−1) but not post-fan trial (p = 0.18). Conclusions: Fan cooling during submaximal, moderate-high intensity cycle ergometry significantly enhanced work capacity and energy expenditure without increasing perceived exertion. Practical Applications: These data highlight the utility of fan cooling as a means to increase the effectiveness of heart rate-based cycle training.

(39) The Effects of Music and Music Tempo on Aerobic Performance

Z. Von Ruff,1 B. Valdez,1 B. Valdez,1 R. Pifer,1 M. Choate,2 J. Dean,1 and W. Amonette2

1University of Houston-Clear Lake; and2University of Houston—Clear Lake

Music has been shown to be an effective strategy to improve various aspects of exercise performance and enjoyment. However, the effects of music tempo on exercise outcomes have not been adequately explored in the current research. Purpose: The aims of this study were to identify potential associations between music tempo, performance measures, and exercise enjoyment. We hypothesized that faster tempo is associated with increased aerobic performance. We further hypothesized that enjoyment after a bout of moderate intensity exercise would be greater with music of any tempo compared to no music. Methods: We recruited 5 subjects aged 18–50 (age 22.4 ± 3.05 [mean ± SD], height 176.92 ± 7.83 cm, weight 73.6 ± 4.94 kg) by word of mouth and flyer. Using a random number generator to order the conditions, we assigned subjects to perform a self-paced, three-mile run in 3 separate sessions 5 to 7 days apart under one of 3 conditions: no music, slow-tempo music (50–100 b·min−1), and fast-tempo music (>140 b·min−1). Prior to the 3 sessions, each subject performed a treadmill V̇o2 max test. Subjects chose from a researcher-provided bank of songs predetermined to fall within the fast- and slow-tempo ranges. We collected the primary outcomes on a metabolic cart connected to a Bluetooth heart rate monitor: average oxygen consumption (V̇o2, ml·kg−1·min−1), respiratory exchange ratio (RER), heart rate (HR, b·min−1), and time to completion (min:s). Rating of perceived exertion (RPE) was measured using a 6–20 BORG scale, and enjoyment of exercise was measured using the Exercise-Induced Feeling Inventory (EFI). Results: Testing and survey results were calculated as mean ± SD for no music (none), slow-tempo music (slow), and fast-tempo music (fast), respectively: average V̇o2 (none: 37.8 ± 8.1 [mean ± SD] ml·kg−1·min−1, slow: 35.7 ± 6.8 ml·kg−1·min−1, fast: 36.6 ± 6.6 ml·kg−1·min−1); RER (none: 0.91 ± 0.03, slow: 0.91 ± 0.04, fast: 0.89 ± 0.02); average HR (none: 161.3 ± 5.3 b·min−1, slow: 161.0 ± 8.5 b·min−1, fast: 163.3 ± 11.5 b·min−1); time to completion (none: 25:11 ± 5:56 minutes:seconds, slow: 25:21 ± 5:38 minutes:seconds, fast: 25:29 ± 4:01 minutes:seconds); and RPE (none: 16.0 ± 2.0, slow: 16.4 ± 1.5, fast: 15.8 ± 2.5). EFI subscale scores, where higher numbers correlate with stronger feelings (maximum possible score = 12): positive engagement (none: 5.0 ± 3.2, slow: 5.6 ± 2.9, fast: 7.8 ± 2.3); revitalization (none: 5.4 ± 3.3, slow: 6.0 ± 3.2, fast: 6.2 ± 1.8); physical exhaustion (none: 4.6 ± 1.5, slow: 5.0 ± 4.9, fast: 5.2 ± 1.9); and tranquility (none: 8.0 ± 2.6, slow: 7.2 ± 2.5, fast: 7.00 ± 1.22). Conclusions: Findings suggest music did not have a substantial effect on performance outcomes or enjoyment of exercise. Practical Applications: Athletes and recreational exercisers should follow their personal preference when it comes to using music as an outside stimulus during exercise.

(41) Tracking Heart Rate Variability in College Football Players Throughout Postseason Preparation for the National Championship

A. Flatt,1 J. Allen,2 and C. Keith2

1Georgia Southern University; and2University of Alabama

After a physically and emotionally taxing regular competitive season, pressure to achieve peak physical and mental performance rises as teams campaign for a College Football Playoff berth. Despite the magnitude of these events, the physiological impact of postseason training and competition among college football players has received little investigation. Purpose: To characterize autonomic nervous system (ANS) responses in college football players throughout postseason preparation for the National Championship. Methods: Players were categorized as linemen (n = 8, height = 192 ± 5 cm; weight = 135 ± 6 kg) and non-linemen (n = 12, 188 ± 6 cm, weight = 97 ± 9 kg). ANS activity was indexed by intra-individually averaged resting heart rate (RHR) and heart rate variability (HRV) recordings throughout the following time points: preseason (4 weeks baseline); week of the Conference Championship; a playoff preparation week involving training camp-style practices; week of the National Semifinal; and week of the National Championship. HRV was approximated via an optical pulse-wave finger sensor and mobile application. Measurements were performed on training days in the seated position for 60 seconds, standardized for proximity to training sessions and meal time. The application processes and computes RHR and the natural logarithm of the root mean square of successive differences (LnRMSSD). Changes in RHR and LnRMSSD were examined with linear mixed models and effect sizes (ES). Results: RHR for linemen was higher than non-linemen (80.6 ± 9.3 vs. 73.7 ± 6.5 b·min−1, p < 0.05). As a combined group (n = 20), RHR and LnRMSSD at baseline were lower and higher, respectively, than all postseason time points (Table 1). Though position × time interactions were not observed (p = 0.17–0.19), ES demonstrated that increases in RHR for linemen throughout the postseason were of greater magnitude relative to non-linemen (ES = 0.66–1.10 vs. 0.36–0.59). Similarly, reductions in LnRMSSD for linemen throughout the postseason were of greater magnitude relative to non-linemen (ES = −0.72 to 1.27 vs. −0.42 to 0.66). Conclusions: Tracking ANS functioning in college football players throughout the postseason revealed sustained activation of the physiological stress response, which was most notable in players of the linemen position. Practical Applications: As ANS imbalance is a hallmark of training fatigue, performance staff should devise strategies aimed at prevention and mitigation of its occurrence to limit potential decrements in performance and recovery status. Sports medicine staff should be aware that chronic ANS dysregulation in the form of attenuated parasympathetic activity likely contributes to adverse changes in cardiac morphology reported to occur in linemen following a competitive season. Therefore, identifying ANS imbalance as it occurs and intervening with restorative modalities may limit clinically-relevant cardiovascular maladaptations in football players.

Table 1 - Mean and SD for RHR and LnRMSSD.

(42) Aerobic Overtraining Protocol Does Not Affect Performance and Reduces Marker of Central Fatigue

G. Davis, D. Scott, and H. Hardin

University of Louisiana at Lafayette

The central fatigue theory of overtraining syndrome (OTS) states that elevated levels of 5-hydroxytryptamine (5-HT) in the hypothalamus and brainstem plays a role in tiredness and sleep, inhibition of post-synaptic reflexes, inhibition of releasing hormones from hypothalamus. Specifically, it is involved in the stimulation of the secretion of prolactin. Thus, changes in plasma prolactin levels could be used as a surrogate marker of central fatigue in OTS. Purpose: Determine how prolactin levels are affected by 8 weeks of an established aerobic overtraining protocol. Methods: Male C57BL mice were divided into a sedentary control group (CON; n = 6), an exercise group (EXE; n = 6), and an overtraining group (OTS; n = 6). All exercise was performed on a treadmill. Exhaustion velocity (EV) was measured at baseline and repeated post-intervention. Blood was collected at baseline and 2 weeks following the post-intervention EV test. All groups exercised for a total of 8 weeks. The EXE group exercised for 60 minutes at 60% EV, 5 days per week. The OTS group matched the EXE group for the first 5 weeks, then increased to 90 minutes at 90% EV at a −14 percent grade, 5 days per week, 2 times per day, for 3 weeks. All data are presented as mean ± SD.Results: There was a significant group (F = 31.62; p < 0.01), time (F = 91.24; p < 0.01), and interaction effect (F = 9.03; p < 0.01) for performance, as measured by EV. However, EV did not differ between the EXE (24.4 ± 1.7 m·min−1) and OTS (25.0 ± 0.2 m·min−1) groups post-intervention (p = 0.91). There was a significant group (F = 8.18; p < 0.01) and time effect (F = 6.81; p = 0.02), but no interaction effect (F = 6.29; p = 0.06) for prolactin. Levels of prolactin decreased from 192.42 ± 41.22 pg/ml to 124.52 ± 57.02 pg/ml in the CON group (t = 0.05), increased from 155.12 ± 42.27 to 172.23 ± 45.43 pg·ml−1 in the EXE group (t = 0.69), and decreased from 148.34 ± 68.43 to 58.09 ± 14.81 pg·ml−1 in the OTS group (t = 0.01). Conclusions: The data suggest that the downhill running protocol did not overtrain the mice based upon performance. A decrease in prolactin levels suggest reduced central fatigue in the OTS group. Practical Applications: Exercise performance values were not different between the lower volume, lower intensity exercise protocol (EXE) and the higher volume, higher intensity protocol (OTS). Although the OTS group was not overtrained, the performance data reinforce the concept that more training does not necessarily equate to greater exercise performance. Further research in overtrained athletes is required to determine if plasma prolactin levels could be an effective marker of OTS as it pertains to central fatigue.

(43) Metabolic and Cardiovascular Comparison of Interval-Based Treadmill and Bodyweight Exercise Regimens

R. Snarr,1 E. Langford,2 and G. Hogan1

1Georgia Southern University; and2University of Kentucky

Bodyweight circuits have gained popularity as a time-efficient method to improve aerobic fitness. These regimens exhibit heart rates (HR) near an individual's maximum; however, metabolic responses (i.e., maximal oxygen uptake [V̇o2max]) have displayed moderate values. With metabolic stress being a key component in improving aerobic capacity, it is important to quantify physiological demands to determine program effectiveness. Purpose: The purpose was to examine cardio-metabolic differences between interval-based regimens consisting of either treadmill only or bodyweight exercises. Methods: Ten males (n = 5) and females (n = 5) underwent 4 days of testing to determine cardio-metabolic responses. On day one, subjects completed a graded exercise test (GXT) to determine V̇o2max. For the remaining trials, individuals completed each of the following on separate days: (a) Treadmill interval (TIVO2): intervals at intensity used to elicit V̇o2max; (b) Bodyweight circuit (BWC): burpees, mountain climbers, squats, and jump squats; (c) Treadmill interval (TIBWC): intervals at intensity to match the metabolic cost of the BWC. Each routine was randomized with a work-to-rest ratio of 2:1. A portable metabolic system and heart rate strap were used for all sessions to measure V̇o2, HR, and caloric expenditure (kcal·min−1). Ratings of perceived exertion (RPE) were gathered for each session for subjective scores of difficulty. A 3 × 3 repeated measures analysis of variance, with a Bonferroni post-hoc, was run to examine differences between sessions (a priori α = 0.05). Effect sizes and probability sampling (PSdep) were used to determine practical significance. RPE was assessed using non-parametric comparisons. Results: All data is provided in Table 1. For %V̇o2max, results indicated large and moderate effects between TIVO2 and TIBWC (ES = 2.15), TIVO2 and BWC (ES = 0.50), BWC and TIBWC (ES = 1.96). For %HRmax, no difference was observed between TIVO2 and BWC (trivial effect); however, there was a ∼10% decrease in HR response for TIBWC (TIVO2 ES = 1.9; BWC ES = 3.1). Findings indicated a mean decrease of 2.5–3 kcal/min when individuals performed the TIBWC (TIVO2 ES = 1.5; BWC ES = 1.2). RPE did not differ between TIVO2 and BWC; although, TIBWC displayed a lower overall RPE (14.5 vs. 11.5; PSdep = 1.0). Conclusions: Results demonstrated large practical differences between TIBWC and the other interval routines. Findings are consistent with previous literature demonstrating moderate-to-high HR responses during interval routines. However, all routines were classified as moderate activity based on metabolic demands (i.e., <64%). Practical Applications: While results of the investigation showed no differences in the observed variables between TIVO2 and BWC, neither regimen obtained metabolic stress values necessary to elicit large adaptations to aerobic capacity in trained individuals. Thus, for trained individuals looking to improve cardiorespiratory fitness, greater intensities are required.

Table 1 - Metabolic and cardiovascular demands of interval-based exercise routines (reported as mean and SD).

(45) Physiological Characteristics of Competitive Masters-Level Rowers: A Comparison Amongst Varying Age Groups

M. Grammenou,1 K. Cardwell,1 and K. Kendall2

1Edith Cowan University; and2Center for Exercise and Sports Science Research, Edith Cowan University

Although there is considerable amount of research describing the physiological characteristics of competitive junior and senior-level rowers, these same characteristics in Masters-level rowers is lacking. High levels of physiological function, such as maximal oxygen consumption (V̇o2max), peak power output (PPO), and metabolic thresholds (i.e., ventilatory threshold (VT) and lactate threshold (LT) are strongly associated with rowing performance, and are often used to identify the training status of an athlete. However, due to physiological changes associated with aging, comparing these variables between younger and older rowers may result in inappropriate categorization of these athletes. PURPOSE:T he purpose of this study was to (a) establish a physiological profile for Masters-level rowers; and (b) compare these results to previously published reports for junior, collegiate, national, and international-level rowers. Methods: Twenty one male (n = 7) and female (n = 14) Masters-level rowers performed a graded exercise test (GXT) to volitional exhaustion on rowing ergometer (Concept II, Model D) to determine V̇o2max, PPO, power output at ventilatory threshold (PVT), and maximal heart rate (HRmax). Results: Data is presented as means ± SD. Values for all variables of interest measured during the GXT are presented in Table 1, alongside previously reported data from our laboratory and others. Compared to young adult rowers, Masters-level rowers expressed lower V̇o2max (both absolute and relative), PPO, and PVTvalues. Conclusions: The aim of this study was to determine if Masters-level rowing data can be accurately assessed using established young adult normative data. Findings from this study show V̇o2max, PPO, and PVT decline with age, despite a training frequency of 5.5 and 6.7 h·wk−1 for males and females, respectively. This observation suggests that continued participation in competitive rowing does not necessarily attenuate the age-related declines in aerobic fitness. Practical Applications: Despite continued engagement in rowing activities, competitive rowing does not appear to attenuate the declines in aerobic fitness and muscular power associated with aging. The comparison of physiological indices from Masters-level rowers with normative data from younger rowers can lead to misinterpretation of the data and subsequent inaccuracies in predicting performance and determining training intensities.

Table 1 - Physiological characteristics (mean ± SD) for Masters, Junior, Collegiate, and Elite-level rowers

(46) Validity of Ultra-Short Measurements of Heart Rate Variability Before and After Exhaustive Resistance Exercise

W. Dobbs,1 D. Tolusso,2 M. Fedewa,3 and M. Esco3

1University of Wisconsin-La Crosse;2Western Kentucky University; and3The University of Alabama

The use of heart rate variability (HRV) for monitoring autonomic modulation in field settings has grown in popularity. There is a growing body of research supporting the use of more convenient methods for acquiring HRV, such as ultra-short recordings (recordings of 1-minute). Ultra-short recordings have shown acceptable agreement against traditional short-term (10-minute) recordings, however, the agreement of all HRV metrics, linear and non-linear, acquired through ultra-short analysis remains controversial. Consequently, there is a need to further validate the use of ultra-short recordings across the broad spectrum of HRV metrics at rest and following physical exertion. Purpose: The purpose of this study was to determine the level of agreement between the ultra-short and traditional recording times of a multitude of log-transformed (ln) HRV metrics throughout 6 data collections before and after an exhaustive resistance exercise protocol. Methods: Eight resistance-trained males [mean (SD)] [age = 23.3 (3.9) y, mass = 90.4 (10.9) kg; height = 180.8 (8.3) cm], volunteered to participate in the study. An electrocardiogram with a modified lead II arrangement was used for each HRV assessment while subjects assumed a seated position. The standard, short-term timeframe of a 5-minute epoch following a 5-minute stabilization period was used as the criterion HRV recording. The ultra-short HRV measurement occurred during a 1-minute epoch following a 1-minute stabilization period, which took place during the first 2-minute of the criterion stabilization period. Each HRV measurement occurred at the same time of day (±15 minutes) across 2 baseline days and immediately prior to a resistance exercise protocol consisting of 8-sets of 10 back squat repetitions at an intensity equal to 70% one-repetition max. Additional HRV recordings occurred at 0.5, 24, 48, and 72-hour post-exercise. The level of agreement between the ultrashort and criterion HRV measures at each time point were quantified by two-tailed dependent t-test, two-way mixed intraclass correlation coefficient (ICC) for absolute agreement, Cohen's d effect size (ES), and the Bland Altman method for limits of agreement (LOA). Results: Compared to all HRV metrics, the highest levels of agreement were displayed in the log-transformed root mean square of successive R-R differences (lnRMSSD) [LOA = −0.93– 0.72, ICC = 0.91, ES = −0.14, p = 0.082] and SD of the points through the width of the plot (lnSD1) [LOA = −0.91–0.75, ICC = 0.91, ES = 0.13, p = 0.156]. The lowest level of agreement was displayed in low-frequency (lnLF) [LOA = −3.08 to 1.88, ICC = 0.61, ES = −0.48, p = 0.003]. Conclusions: Our results indicate ultra-short lnRMSSD and lnSD1 obtained in the seated position provided accurate measures compared to the criterion recordings. Furthermore, our findings support previous literature that suggested the ultra-short timeframe of only 1-minute is insufficient for frequency domain parameters, such as lnLF. Practical Applications: As lnRMSSD is becoming one of the most utilized HRV metrics for field settings, the use of ultra-short recordings offer a more efficient means of collection. When compared to the criterion recordings, the accuracy of lnRMSSD and lnSD1 obtained from ultra-short recordings was not influenced by exhausted resistance exercise. Therefore, practitioners should consider using ultra-short recordings of lnRMSSD or lnSD1 when using HRV as an internal indicator of training-related stress.

(47) Using the Critical Speed Concept to Improve Pacing Strategy and 5K Performance in Distance Runners: Two Case Studies

K. Capello,1 L. Wolff,1 M. Kantor,2 R. Pettitt,2 and J. Dexheimer1

1Azusa Pacific University; and2Rocky Mountain University of Health Professions

Optimal pacing strategy is a major component of distance running performance, preventing premature fatigue while also ensuring maximal exertion by the end of the race. For the 5K race distance, most runners adopt one of 2 pacing strategies: either a U-shaped pattern characterized by a faster start and finish or a more evenly paced strategy with a final surge (“kick”). The critical speed (CS) concept is an under-utilized third strategy with the potential to predict and improve 5K performance. Purpose: The purpose of these case studies was to assess whether self-selected pacing strategy and 5K performance in experienced distance runners could be improved by prescribing a pace based on the CS concept from the 3-minute all-out exercise test (3 MT). Methods: A former and current collegiate distance runner (Runner #1: female; age: 23 years; height: 165 cm; weight: 54 kg; BF%: 20.4%; Runner #2: male; age: 19; height: 183 cm; weight: 59 kg; BF%: 5.8%) completed an initial 5K time trial on the track with individual lap splits given. They then completed a customized graded exercise test (GXT) for the attainment of peak maximum oxygen uptake (V̇o2peak) (Runner #1: 53.5 ml·kg−1·min−1; Runner #2: 58.0 ml·kg−1·min−1). This was followed by a 3 MT on the track for the attainment of CS and the finite capacity for exercise > CS, known as distance prime (D′) (Runner #1: CS: 3.98 m·s−1; D': 144 m; Runner #2: CS: 4.17 m·s−1; D': 119 m). 5K time trial performance was predicted by the equation tLIM = (5000-D′)/CS (Equation 1). The running speed associated with this tLIM was found by the equation S = D'/tLIM + CS (Equation 2). The runners were then instructed to run a second 5K time trial at the calculated speed. In addition to individual lap splits, the runners monitored accuracy to the prescribed pace using real-time speed feedback from a GPS watch. Comparisons were made between 5K #1, predicted time from CS and D′, and 5K #2. Results: Runner #1: The finishing time for 5K#1 was 22:15 (7:10/mi, 8.4 mph). The predicted time based on Equation 1 was 20:19 (6:33/mi, 9.2 mph). The finishing time for 5K #2 was 21:35 (6:56/mi, 8.7 mph), which represents a 40-second improvement from 5K #1 and a difference of 76 seconds from the predicted time. Runner #2: The finishing time for 5K #1 was 22:00 (7:04/mi, 8.5 mph). The predicted time based on Equation 1 was 19:30 (6:16/mi, 9.6 mph). The finishing time for 5K #2 was 21:42 (6:59/mi, 8.6 mph), an improvement of 18 seconds from his initial 5K and a 162-second difference from the predicted time. Conclusions: Despite the subjects' experience at the competitive level, their self-selected pacing strategy was suboptimal compared to the prescribed pace from the 3 MT. Practical Applications: When performed properly, the 3 MT may enable athletes to run closer to their physiological potential by providing them with an individualized pacing strategy based on their unique CS/D′ profile.

(48) Maximal Effort 3-Minute Rowing Test as Benchmark for 2,000-Meter Time in Female Collegiate Rowers: A Pilot Study

K. Hammond, M. Magrini, and J. Eckerson

Creighton University

Rowing ergometers are commonly used as a training tool for increasing rowing-specific aerobic capacity and provide quantitative, individualized performance data. Historically, 2,000-m time trials have been used to evaluate aerobic fitness, however, these tests are taxing and require adequate recovery. Therefore, a 3-minute maximal effort test may provide a more efficient benchmark for rowing performance that correlates with 2,000-m time with a lower degree of fatigue. Purpose: The purpose of this study was to investigate whether a maximal effort 3-minute rowing test is correlated with 2,000-meter time in female collegiate rowers. Methods: Sixteen female collegiate rowers (means ± SD; age: 19.4 ± 1 year old; experience: 1.3 ± 0.8 years experience) volunteered to participate in the study. On the first day, following a warm-up, the athletes completed a 2,000-m time trial on a rowing ergometer. Total time and average 500-m split times were recorded for each athlete. Nine days later, following the same warm-up, athletes completed a 3-minute, all-out distance trial on the rowing ergometer. Total meters and average 500-m split time were recorded for each athlete. During both rowing trials, athletes were given strong verbal encouragement by testers and teammates to maximize their performance. Descriptive and correlation statistics were calculated using SPSS statistical software (v. 26, IBM, Inc., Armonk, NY). Results: Statistical analysis revealed an average 2,000-m time trial of 8.16 ± 0.49 minutes with an average 2,000-m split of 2.04 ± 0.12 min/500-m. The average 3-minute distance trial of 771.5 ± 41.2 meters had an average of 1.95 ± 0.10 min/500-m split. The 2,000-m time trial was negatively correlated with the meters rowed (r (14) = −0.925, p < 0.001) during the 3-minute distance trial. Further, the 2,000-m time trial was positively correlated with average 500-m split during the 3-minute distance trial (r (14) = 0.922, p < 0.001). Conclusions: These data suggest that a maximal effort 3-minute distance trial was highly correlated with a 2,000-m time trial on a rowing ergometer. Although this sample is small and the athletes were relatively new to the sport, the strong, positive correlations found herein suggest that the 3-minute test may be a time efficient assessment of rowing performance between 2,000-m tests. Practical Applications: Strength and conditioning professionals, coaches, and practitioners may elect to use the less systemically-taxing 3-minute test to track fitness progress in rowers during the winter season in preparation for moving outdoors onto the water.

F9
Figure 1.:
2,000-meter rowing time is negatively correlated with 3-minute distance trial.

(49) No More of the Same Old Same: Strength and Conditioning Coaches Learning to Generate New and Creative Movement Practices

C. Kuklick1 and B. Gearity2

1University of Denver; and2University of Denver

Normative strength and conditioning (S&C) coaching practices are informed by biophysical sciences (i.e., biology and technology). Researchers have demonstrated that these practices elicit desirable physiological outcomes for athletic performance, however, sociologists of sport have shown that when such practices are used regularly (i.e., dominant), they produce docile, apathetic, and underperforming athletes. Social scientists, using Foucault's disciplinary theoretical framework to guide their research, have shown in many studies how negative outcomes are produced from coaches' control of time, space, flow, and efficiency, which coerces athletes' adherence and supports and reproduces coaches' reliance on biophysical knowledge. Purpose: The purpose of this case study was to examine how S&C coaches learn to problematize disciplinary practices and create new and creative practices. Methods: Three S&C coaches and 2 coach developers participated in a sociological intervention where disciplinary practices (i.e., the control of time, space, flow) were presented and discussed in regular learning community meetings. Data were collected from 7 learning community meetings, coaching observations and debriefs, interviews, and personal communications. Data were analyzed by coding the initial meaning units and then grouping them into subthemes and themes, which explained how coaches learned to problematize disciplinary practices, and resultantly, developed and implemented new and creative coaching practices. Findings: The learning community meetings, which formulated the sociological intervention, contained various facilitators and barriers to S&C coaches learning to problematize disciplinary practices. These facilitators and barriers either initiated or impeded the learning to problematize disciplinary practices process and the creation of new and creative movement practices. The learning process began with epiphanic contradictions to modernity, which were “aha” moments where S&C coaches realize paradoxes to normative and traditional coaching truth regimes. After S&C coaches had an epiphany that changes to typical disciplinary practices are possible, they rationalized the alternatives. Coaches justified how and why alternatives to disciplinary practices are appropriate or fathomable. After contemplating alternative rationales, catalytic mediators were forces that affected the likeliness of S&C coaches to adopt and implement the new and creative practice into their coaching. Catalytic mediators included situations outside of the learning community that created comfortable opportunities for coaches to use new and creative coaching practices. The specific facilitators, barriers, epiphanies, rationalizations, and catalytic mediators impacting the learning process will be provided in the full poster presentation. Conclusions: This sociological intervention study is the first study to investigate how S&C coaches learn to problematize dominant coaching practices. The findings provide an understanding for how S&C learn to change their practices. Practical Applications: S&C practitioners benefit from this research by understanding how to diversify their knowledge, create new and creative practices, and facilitate a coaching staff's ability to problematize disciplinary practices. Likewise, coach educators can better facilitate coaches' understandings of their use of power, knowledge, and how to create novel practices.

(50) Harmony in My Practice, Conflicts in My Head: Values Squeeze and Job Satisfaction in Strength and Conditioning Coaches

P. Handcock,1 T. Cassidy,2 and B. Gearity3

1Institute of Sport, Exercise & Health, Otago Polytechnic;2School of Physical Education Sport and Exercise Sciences, University of Otago; and3University of Denver

Professional integrity has traditionally been considered to depend on espoused personal values, moral concerns, and deeds (Tomlinson et al., 2014; Orvik et al., 2015). Values can, in turn, determine an individual's professional ethical behaviours, and how they conceptualize, contemplate, and prioritize their work. Yet, these elements of professionalism are rarely explored in strength and conditioning (S&C) (e.g., Masey & Manual, 2014). In healthcare settings, professions' organizational constraints have resulted in organizational values that are often at odds with personal and professional values - described as ‘values squeezing’ (Siebert & Costley, 2003; Orvik et al., 2015). S&C is a relatively new profession, so it is unclear how its members acquire their professional values, and how they reconcile personal and professional values with organizational values. Purpose: The purpose of this qualitative study was to consider the professional values of strength and conditioning coaches (SCCs) and their congruence with personal and organizational values. Methods: Using convenience sampling, 11 full-time SCCs (mean = 7.3 years experience), working in US NCAA Division 1 collegiate athletic programs, agreed to participate in face-to-face interviews that sought their interpretations of values pertaining to their employment. Using grounded theory, transcribed interviews were analysed using open coding, followed by focused coding to ‘sift, sort and synthesise’ key themes (Charmaz, 2006). Findings: Subjects described strong nurturing personal values that privileged a holistic vision of athlete wellness and wellbeing. Their professional values typically focused on protecting and advancing the integrity of the profession through educating themselves and others, and by building harmonious professional interactions. Most reported “values squeeze” when contemplating the agendas and expectations of sport coaches and administrators. These organisational expectations were often perceived to be in conflict with personal values pertaining to athlete care, and professional ideologies and values concerning best practice. In particular, the management of injured athletes and the use of conditioning to promote toughness conflicted with subject values. Conclusions: The intersection of personal and professional values were described by subjects as reasons they chose and enjoyed S&C. Yet the conflict between those values and organizational values were a source of ongoing discontent. Nonetheless, subjects were optimistic that educating others offered a positive pathway to resolving those tensions. Practical Applications: Values squeeze occurs in S&C work, with SCCs aware of these conflicts which impacted on their job satisfaction and left SCCs feeling professionally marginalised. Improved communication, reflection, and re-educating self and others on the stereotypical perceptions of S&C, can allow SCCs to share their professional values with decision makers to help reduce or remove values squeeze and improve professional standing.

(51) Comparison of the Effects of Moderate Intensity Aerobic and High Intensity Interval Training on Cognitive Function

T. Keating, K. Kalaj, and M. Doyle

Manhattan College

Purpose: Moderate-intensity aerobic exercise is shown to acutely improve working memory. Recent studies suggest that high-intensity interval training (HIIT) is more efficient in improving aerobic capacity than moderate-intensity aerobic exercise. However, effects of HIIT on cognition are still uncertain. Thus, in this study we sought to directly compare the effects of moderate-intensity aerobic exercise and HIIT on cognitive function after recovery. Methods: Eight healthy subjects between 18 and 21 years of age from the Manhattan College student population each participated in a control trial, a moderate-intensity aerobic exercise protocol, and a HIIT protocol. The moderate-intensity aerobic intervention involved a 30-minute treadmill session at 50% heart rate reserve. The HIIT intervention consisted of 2 sets of thirty-second burpees with a one-minute recovery interval in between the sets, with a warm-up and a rest period before and after the activity. To measure improvements in cognitive function, a Stroop color-word task was completed before and after exercise. Results: Dependent t tests showed that all conditions significantly decreased in reaction time (p < 0.01). Only the control and HIIT conditions showed increased response accuracy (p < 0.05). Conclusions: Results demonstrated that neither moderate intensity aerobic exercise nor HIIT improved reaction time more than the control during the Stroop task, and HIIT was the only exercise intervention to result in increased response accuracy. Practical Applications: While more data are needed, coaches and fitness professionals may be confident that short-term HIIT fails to impair and may possibly enhance some aspects of cognitive function.

(53) The Effect of Body Composition on CD8+ T Cell Activation: A Pilot Study

M. Padgett, J. Sparks, E. Bredahl, and J. Siedlik

Creighton University

Cytotoxic, or CD8+, T cells are the foot soldiers of the adaptive immune system in that they can recognize and destroy virally infected and/or cancerous cells. Activation of this subset of cells can occur under a variety of disease conditions and, consequently, may be exposed to vast array of cytokine signals. Fat tissue is a potent endocrine organ that generates low-grade, chronic inflammation that could potentially alter cytotoxic T cell activation. Purpose: To quantify the relationship between body composition and CD8+ T cell activation states following in vitro cell stimulation. Methods: Using an observational study design, 14 (12 males, 2 females) subjects (age: 24 ± 6 years; height: 180 ± 7 cm; weight: 86.1 ± 9.2 kg) participated in this study. Body fat percentage was measured via air displacement plethysmography (BodPod) and each subject completed an extensive health history questionnaire. Fasted venous blood samples (20 ml) were collected and CD3+ T cell isolation from peripheral blood was conducted through negative selection using a Human CD3+ T cell enrichment kit (Stemcell Technologies, Vancouver, BC, Canada). Cells were stimulated via plate bound antibodies and analyzed in response to co-stimulation through CD28. Cells were incubated for 3 days at 37° C in a humidified incubator with 5% CO2 and then analyzed by flow cytometry. Activation states were assessed by quantifying both the percent of the total cells expressing CD25 and the median fluorescence intensity (MFI) of CD25 expression. Regression equations were calculated to estimate the effect of body fat percentage on CD4+ T cell activation state while adjusting for age. Results: Neither body fat percentage (b = −0.004, p = 0.9) nor age (b = −0.08, p = 0.2) were significant predictors for the percent of CD4+CD25+ T cells following in vitro stimulation. Intensity of CD25 expression (MFI) was also not significantly predicted by either body fat percentage (b = −0.02, p = 0.6) or age (b = −0.05, p = 0.3). Conclusions: The generalizability of these results is limited due to the small sample size at this time. Of note, however, is that in this limited sample the effects of percent body fat and age remain relatively stable in that measures of activation are inversely related to both variables. It is anticipated that other health variables need to be controlled for and will be included in statistical models as sample size increases. Practical Applications: Athlete health and resilience to training stress is of the utmost importance. Improved understanding of how body composition moderates immunosurveillance capabilities will help coaches better manage concerns related to athlete health particularly for those involved in weight regulated sports.

(54) Relationship Between Anaerobic Performance and Fat-Free Mass Assessed From a 2D Image Processing System in NCAA D1 Female Rowers

C. Metoyer,1 K. Sullivan,2 B. Hornikel,2 C. Holmes,3 M. Esco,2 and M. Fedewa2

1University of Alabama;2The University of Alabama; and3Washing University School of Medicine

Fat-free mass (FFM) is an important body composition metric that is strongly associated with athletic performance. However, FFM is not commonly assessed in practical settings for several reasons. For instance, the most accurate methods are mainly found in research laboratories and are generally less accessible to practitioners. On the other hand, the ranges of error associated with the available field techniques are exacerbated with improper technique and minimal formal or standardized training. Thus, practitioners need simple assessment methods when evaluating FFM and its association with athletic performance. Purpose: The purpose of this study was to determine if the relationships between anaerobic performance from a Wingate test and FFM were different when FFM was assessed from 3 different methods: a portable 2D digital image processing system (FFMIMAGE), the skinfold technique (FFMSKF), and underwater weighing (FFMUWW). Methods: A convenience sample of 18 female NCAA division 1 rowers (age = 20.4 ± 1.0 years, body mass index = 24.3 ± 2.6 kg·m−2) were recruited for this study. A single 2D digital image of each subject was taken from the rear/posterior view using a 12.9 inch, 64 g iPad Pro. From the image, body volume was estimated using an automated image analysis program (U.S. Provisional Patent 62/842,826) and then converted to FFMIMAGE. Additionally, FFMSKF and FFMUWW were determined from the Jackson-Pollack 7-site skinfold technique and underwater weighing, respectively. Anaerobic sprint performance was assessed using a 30-second maximal effort Wingate sprint, with average power (PWRAVG) and peak power (PWRPEAK) serving as the primary outcomes of interest. Repeated measures ANOVA was used to assess potential differences between FFM measures. Bivariate correlations between sprint performance and the FFM measures were assessed using Pearson's r and R2, and directly compared using Fisher's r to z transformation. Results: FFMIMAGE (59.2 ± 5.0 kg) was not different from FFMSKF (58.9 ± 4.5 kg) or FFMUWW (58.3 ± 4.9 kg) (p > 0.99 and p = 0.11, respectively). FFMIMAGE (r = 0.66), FFMSKF (r = 0.61) and FFMUWW (r = 0.61) were all significantly correlated with PWRAVG (r values ranged from 0.61 to 0.66, p < 0.05) and PWRPEAK (r values ranged from 0.60 to 0.63, p < 0.05). When comparing the correlations coefficients, no significant differences were found between the FFM methods and either PWRAVG or PWRPEAK (all p values >0.05). Conclusions: The findings of the study demonstrated that mean FFM values were comparable between the 2D image processing system, 7-site skinfold method, and UWW. In addition, FFMIMAGE correlated with PWRAVG and PWRPEAK just as well as FFMSKF, and FFMUWW. More research is needed to further determine the suitability of the 2D imaging method for relating body composition to performance among other athletic populations. Practical Applications: Practitioners are presented with a novel method of estimating body composition parameters, such as FFM, from a single 2D image. The method appears to agree with traditional techniques for both measuring FFM and associating it with anaerobic performance.

(56) Relationship Between Rowing Performance and Fat-Free Mass Assessed From a Novel 2D Image Processing System

C. Holmes,1 K. Sullivan,2 B. Hornikel,2 M. Esco,2 and M. Fedewa2

1Washing University School of Medicine; and2The University of Alabama

Body composition is strongly correlated with athletic performance, especially among rowers. Unfortunately, laboratory-based methods used to assess parameters such as fat-free-mass (FFM) are often time-consuming and cannot be performed in field settings. However, a novel method of measuring FFM from a single 2D image has been proposed as a surrogate to laboratory techniques, such as underwater weighing (UWW). Purpose: The purpose of this study was to determine if the association between rowing performance and FFM was similar when FFM was measured from either a 2D digital image (FFMIMAGE) or UWW (FFMUWW). Methods: A convenience sample of female NCAA Division 1 rowing athletes (n = 16, ages = 20.4 ± 1.0 years, body mass index = 23.8 ± 2.1 kg·m−2), were recruited for this study. A single digital image of each subject was taken from the rear/posterior view using a 12.9 inch, 64 g iPad Pro, and used to estimate FFMIMAGE using an automated image analysis program (U.S. Provisional Patent 62/842,826). Criterion FFMUWW assessment was derived from UWW. Rowing performance was determined from timed-trials over both 2-kilometer (2K) and 6-kilometer (6K) distances on an indoor rowing ergometer. A paired-samples t-test was used to assess potential differences between body composition measures. Bivariate Pearson's correlations coefficients (r) were used to determine the relationships between the FFM measures and rowing performances. Data are presented as mean ± SD, with p < 0.05 used to determine statistical significance. Results: FFMIMAGE was strongly correlated with FFMUWW (r = 0.94, p < 0.001), with no significant differences observed between the measures (58.5 ± 4.2 kg vs. 57.8 ± 4.5 kg, respectively, p = 0.10). FFMIMAGE (r = −0.59, p = 0.016) and FFMUWW (r = −0.61, p < 0.011) were significantly correlated with 2K time. Although FFMIMAGE and FFMUWW were also moderately correlated with 6K time (r = −0.46 and r = −0.43) neither was statistically significant (both p >0 .05). Conclusions: FFMIMAGE was strongly correlated and comparable to FFMUWW, with no differences observed between measures. Although FFMIMAGE and FFMUWW were associated with 2K time and 6K time, the correlations were moderate and indicate that FFM may serve as a better predictor of performance in shorter distance rowing events. Practical Applications: The 2D image system is comparable to UWW for both measuring FFM and associating it with rowing performance. Thus, practitioners are encouraged to utilize this novel method for estimating body composition in athletic field settings.

(58) Relationship of Body Composition Components to 1.5-Mile Run Performance in Air Force Men

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

1Kirtland Air Force Base;2United States Military Academy; and3Truman State University

Currently, Air Force men undergo routine waist circumference (WC) screening as a component of physical fitness testing. The most important element of this testing is the endurance run, as it constitutes 60% of the total score. Lacking are determinations of the effect of body composition elements on endurance running performance in Air Force men. Purpose: To evaluate the relationship of selected body composition components to 1.5-mile run in active-duty Air Force men. Methods: Active-duty men (n = 123, age = 28.4 ± 6.0 years, height = 178.7 ± 7.0 cm, weight = 85.6 = 12.3 kg) volunteered to be evaluated for body composition using air displacement plethysmography and to perform a 1.5-mile run. Height and weight were used to calculate BMI (kg·m−2). Body composition components include fat mass (FM), fat-free mass (FFM), fat-free mass index (FFMI), fat mass index (FMI), and percent body fat (%fat). Waist circumference (WC) was measured at the level of the iliac crest and used to calculate a body shape Index (ABSI) and a body roundness index (BRI). A randomly selected validation groups (n = 100) was not significantly different in age, height, or weight from a cross-validation group (n = 23). Results: Principle components factor analysis isolated 3 components. Component 1 was dominated by fat measurements (FM, FMI, and BMI). Component 2 was dominated by lean measurements (FFM and FFMI). Component 3 was dominated by ABSI. Using these factors in a stepwise multiple regression produced the following equation: Run time (seconds) = 589.40 + 18.946 BMI − 18.881 FFMI (R = 0.63, SEE = 61.7 seconds, CV = 8.8%). Applying this equation to the cross-validation sample resulted in a predicted run time (705.1 ± 53.7 seconds) that was nonsignificantly (p = 0.73) lower than actual time (710.4 ± 94.0 seconds) and moderately correlated (r = 0.65, p < 0.01). Heavier airmen (>80 kg, n = 46) were significantly older (30.1 ± 5.5 years), had greater %fat (26.0 ± 6.4%), and slower run time (732.1 ± 71.7 seconds) than lighter airmen (<70 kg, n = 46, 26.5 ± 5.1 years, 15.5 ± 6.8%, and 667.1 ± 71.7 seconds, respectively). Every kilogram of FM adds approximately 5.5 seconds to the 1.5-mile run time. Kilograms of FFM did not seen to have a measurable effect. Conclusions: Greater proportions of body fatness appear to moderately and negatively affect a continuous endurance task among active-duty Air Force men. Practical Applications: Body size and fatness may have a negative effect on continuous endurance tasks such as a 1.5-mile run. Quantification of this effect allows the prediction of improvement in 1.5 mile run time by the loss of excess body fat. By contrast, FFM does not appear to significantly affect run time. As a result, Airmen should be encouraged to lose FM and gain FFM without concern that FFM will result in slower 1.5 mile run times.

(59) Relationship Between Bone Mineral Density and Handgrip Strength in Collegiate Athletes

S. Lanham, G. Hogan, R. Snarr, and G. Ryan

Georgia Southern University

Background: Bone mineral density (BMD) and hand-grip strength (HGS) may provide useful quantitative information in regards to an athlete's resistance training regimen. Due to stress placed on bones during resistance training, it is feasible that stronger athletes may have increased BMD. Purpose: To determine the relationship between BMD and HGS in male and female Division I collegiate athletes. Methods: A total of 53 (male = 19, female = 34) collegiate athletes participated. BMD was determined using dual energy x-ray absorptiometry (DEXA) and HGS was assessed with a dynamometer. Each subject completed 2 trials of HGS, alternating with each hand, and the best result was used for analysis. Pearson's product correlations were used to determine the significance of the relationship between BMD and dominant hand grip (DHG) and non-dominant hand grip (NDHG) for all athletes, and within each gender. Results: For the entire group, results indicated a nonsignificant weak positive correlation between BMD and DHG (r = 0.19, p = 0.19) and NDHG (r = 0.23, p = 0.10). Nonsignificant relationships between BMD and HGS existed when factored by gender for male (DHG: r = −0.37, p = 0.13; NDHG: r = −0.27, p = 0.27) and female (DHG: r = 0.11, p = 0.57; NDHG: r = 0.11, p = 0.55). Conclusions: While athletes may have higher BMD than non-athletes, it does not appear that BMD variations among athletes can be contributed directly to upper body strength.

(60) Expedited Protocol for the Bottle Buoyancy Method of Body Composition Assessment

R. Pettitt,1 C. Pettitt,1 S. Fretti,1 M. Kantor,1 J. Dexheimer,2 N. Dicks,3 and M. Kramer4

1Rocky Mountain University of Health Professions;2Azusa Pacific University;3Concordia College; and4North West University/Potchefstroom 2520, South Africa

The bottle buoyancy method (BBM) relies upon a reversal of Archimedes' principle whereby those with greater body density (BD) require a higher volume of air within the bottle to establish neutral buoyancy (i.e., neither float nor sink). Stronger validity and reliability of the BBM in comparison to bioelectric impedance analysis (BIA) has been observed using air displacement plethysmography and hydrostatic densitometry (HD) as criterion measures. Unfortunately, when implementing the published protocol with university athletic programs, we observed that the protocol took longer than anticipated (∼30 minutes) despite using trained testers and black lines marked on the bottle to assist faster measurement of pouring and adding water to the bottle. We asked one the most efficient testers: “what's your secret?” He stated, “I guess their percent body fat (BF%) and then pour out what I think would be closest.” That revelation led to the purpose of the present study. Purpose: We examined if a new expedited protocol for the BBM would reduce the time for testing. Methods: Twenty-one testers naïve to the BBM volunteered to conduct our expedited protocol inside of a pool using 12.15 L bottles. The testers received brief instruction which included a video on the technique without physical practice. A series of equations, aided by pre-loaded spreadsheet, calculated the initial volume to remove from the bottle. The basis of the equation is as follows: H2O volume removed (L) = %BFBIA →(a) Db →(b) Ht & Age (RV) →(c) pool temp correction →(d) BM, where arrow (a) is a reversal of the Siri equation to estimate body density (Db) from %BFBIA determined with a handheld device valued at $100 USD, arrow(b) is estimation of residual volume (RV), arrow (c) corrects for water density, and arrow (d) adjust final measure relative to BM (see Table for full script). Should the bottle and subject sink upon full exhalation, a metered syringe was used to add 500 ml to the bottle and conversely 500 ml would be removed should the bottle and subject float. Hypothetically, the volume of air associated with neutral buoyancy would be equivalent to the underwater mass (1 L = 1 kg) using HD; therefore, the standard equation to calculate Db for HD is used for the BBM and ultimately the Siri equation to estimate BF%. Results: The M ± SD measures of BF% in the present study were fairly diverse (21.5 ± 6.5; low = 9.6, high = 30.3). Consistent with the original study, variation between BBM and BIA for the 21 testers was 2.7 %BF. The total duration for the expedited protocol was 6.80 ± 3.44 minutes. Conclusions: We observed naïve testers with the expedited protocol implement the BBM in less than 1/3 of the time of experienced testers. Practical Applications: The expedited BBM represents a convenient, low-cost method of estimating BF% on a large scale basis; however, strength and conditioning professionals should have an alternative option for those uncomfortable fully exhaling while submerged in a pool.

Table 1 - Script for estimating volume of water to remove from a 12.15 L bottle at the start of the BBM using %BF from BIA.
= IF(male = 1, BM − ((((BM/(4.57/((%BFBIA/100) + 4.142)) + (((0.033*((Height*100)/2.54)) + (0.022*Age) − 1.232) + 0.1))*((Pool temperature*-0.0003) + 1.004627)) + 0.18)),BM-((((BM/(4.57/((%BFBIA/100) + 4.142)) + (((0.046*((Height*100)/2.54)) + (0.016*Age)-2.003) + 0.1))*((Pool temperature*-0.0003) + 1.004627)) + 0.18))), where BM is in kg, standing height is in m, pool temperature is in C.

(61) Body Fat Percentage Estimation From 2-Dimensional Digital Image Analysis Compared to DXA and a Multi-Compartment Model in Competitive D1 Swimmers

B. Hornikel, K. Sullivan, M. Esco, and M. Fedewa

The University of Alabama

Body fat percentage (BF%) is often assessed in competitive swimming due to its relationship to in-water performance. However, obtaining accurate measures with most field techniques is questionable and multi-compartment models can be time consuming and costly for an entire team. Recently, a novel method has been developed for estimating BF% from a single 2D image of a person standing in anatomical position. Though the simplicity of the approach is attractive, validation research is lacking. Purpose: The purpose of this study was to determine the agreement between BF% measures from a 2D digital image application (BF%IMAGE), dual-energy x-ray absorptiometry (BF%DXA), and a laboratory-based multi-compartment model (BF%4C) in a sample of D1 swimmers. Methods: A convenience sample of 20 subjects from the University of Alabama Division-1 swim team was recruited for this study (55% female, 75% Caucasian, 20.00 ± 1.27 years, 22.98 ± 1.61 kg·m−2). Body mass was measured (to the nearest 0.1 kg) with a calibrated digital scale (Tanita BWB-800, Tanita Corporation, Tokyo, Japan), and standing height was measured (to the nearest 0.1 cm) with a stadiometer (SECA 213, Seca Ltd., Hamburg, Germany). A single digital image was taken of the subjects from the rear/posterior view using a 12.9 inch, 64 g iPad Pro. The subjects stood in anatomical position while wearing compressive clothing. Body volume (BV) was estimated using an automated image analysis program (U.S. Provisional Patent 62/842,826) and was converted to BF%IMAGE with the Siri equation. BF%DXA was measured using DXA (Lunar Prodigy, v 14.10.022, GE Healthcare, Madison, WI). For the criterion 4C, BV and bone mineral content were assessed with dual energy x-ray absorptiometry, while total body water was derived from bioimpedance spectroscopy. The method of Lohman et al. converted the variables into BF%4C. A repeated measures ANOVA was used to assess potential differences between body composition measures. Bivariate correlations between body composition measures were assessed using Pearson's r. Data are presented as mean ± SD, with p < 0.05 used to determine statistical significance. Results: BF%IMAGE (14.7 ± 6.2%) was comparable to the criterion BF%4C (14.3 ± 5.0%) with trivial non-significant differences noted between measures (ES = 0.07, p > 0.99). In contrast, BF%DXA (18.2 ± 5.3%) overestimated when compared to the criterion, with large difference observed between the 2 measures (ES = 0.78, p < 0.001). The correlations between BF%IMAGE and BF%4C (r = 0.70, SEE = 3.7%) and between BF%DXA and BF%4C (r = 0.83, SEE = 2.8%) were not significantly different from each other (p = 0.25). Conclusions: When compared to a 4C model, the studied method of predicting BF% from a 2D image showed no mean difference, a strong correlation, and an acceptable SEE within a relatively small sample of D1 swimmers. In addition, the correlations and SEE were comparable to DXA, with a significantly smaller constant error. Additional research comparing BF%IMAGE to more advanced multi-compartment modeling in other athletic and non-athletic populations is needed. Practical Applications: The BF%IMAGE appears to offer an acceptable method for estimating BF% in practical settings, and may be a viable alternative to DXA when access to this technology is limited. Requiring only a single 2D photo, this approach for estimating BF% may be simpler compared to other commonly used field methods.

(63) A Comparison of Rapid Weight Loss Practices Within Regional, National and International Powerlifters

T. Gee, P. Campbell, M. Bargh, and D. Martin

University of Lincoln

Purpose: Rapid weight loss (RWL) strategies are common practice amongst strength sport athletes, in order to “make weight” for a chosen bodyweight class. The aim of this study was to compare the rapid weight loss practices of International Powerlifting Federation (IPF) Powerlifters from Great Britain competing at regional, national and international level. Methods: Subjects (n = 51, of which male = 33, female = 18, age; 30.2 ± 8.0; competitive experience; 6.2 ± 6.6 years) were recruited from both Equipped and Classic category IPF lifting populations (mandatory 2 hour competition weigh-in) via a direct approach at training venues and competitions. Subjects were categorised and grouped based on their highest level of competition within the previous 12 months (Regional = 15, National = 19, International = 17). The previously validated Rapid Weight Loss Questionnaire (RWLQ) (Artioli et al., 2010) was used to establish the common weight making practices and the magnitude of RWL across groups. The questionnaire was adapted to include questions on practices of “hot water immersion,” “hot salt water immersion” and “water loading.” Results: Of total responses, 96% of subjects surveyed had previously purposely acutely reduced bodyweight to compete, with an average acute bodyweight loss leading into competition of 3.4 ± 2.1 kg. International competitors demonstrated a lower habitual bodyweight loss (2.1 ± 1.2 kg) when compared to regional (4.5 ± 2.5 kg, p = 0.001) and national (3.7 ± 1.8 kg, p = 0.03). One-week post competition, regional (4.2 ± 2.7 kg) and national (3.6 ± 1.8 kg) competitors re-gained more bodyweight (p < 0.05) than international (1.9 ± 1.3 kg). The RWL score for the sample was 23.8 ± 9.5. There was no significant difference in RWL score across groups (p > 0.05), however, there was a tendency for higher RWL scores for regional (24.2 ± 9.4, d = 0.43) and national (26.6 ± 10.3, d = 0.66) when compared to international (20.5 ± 7.9). The most common time allocated to cut bodyweight before competition was 0–7 days (47%), followed by 8–14 days (35%), then 15 days and over (18%). For RWL methods used, frequencies of “always” and “sometimes” were reported highest for “fluid restriction”’ (88%), “water loading” (63%) and “skipping one or 2 meals” (49%). “Saunas” (22%) and “hot salt water immersion” (20%) were used less frequently. Individuals who were “very influential” and/or offered “some influence” to weight loss practices were athletes within the same sport (65%), coaches (56%) and internet sources (50%). Conclusions: The prevalence of RWL is high amongst competitive Powerlifters across regional, national and international levels. Regional and national level competitors demonstrated a significantly higher pre-competition bodyweight loss and subsequent bodyweight gain one week post competition. RWL methods commonly adopted were fluid restriction, water loading and skipping one or 2 meals. Practical Applications: Regional and national standard Powerlifters should consider if cutting weight to meet a specific bodyweight category is benefiting their performance since international competitors were shown to reduce bodyweight pre-competition to a smaller extent. Additionally, gaining nutritional advice from an appropriately certified professional may support bodyweight management post competition and prevent large weight cuts leading into future competitions.

(64) The Relative Accuracy of Body Composition Assessed via Body Mass Index and a 2-Dimensional Digital Image Compared to a 3-Compartment Model

K. Sullivan,1 B. Hornikel,1 C. Holmes,2 M. Esco,1 and M. Fedewa1

1The University of Alabama; and2Washing University School of Medicine

Multi-compartment models of body composition provide health and fitness professionals with the most accurate measures of adiposity. However, laboratory-based, multi-compartment measures are often time-consuming, expensive, and require trained personnel to perform. In addition, the equipment needed can be complex and not portable. Simple, portable, and accurate field-based methods of body composition assessment are of tremendous interest to practitioners and provide a more practical means of estimating body composition. Due to its simplicity and noninvasive nature, Body Mass Index (BMI)-based percent body fat (BF%) estimates are commonly used as an alternative to lab-based methods. An automated image analysis program was recently developed to measure BF% from a single digital image (BF%IMAGE), however it has yet to be extensively validated against a multi-compartment criterion. Purpose: The purpose of this study was to determine the relative accuracy of BMI-based BF% and BF%IMAGE field-methods when compared to a criterion 3 compartment model (BF%3C). Methods: A convenience sample of 28 adults was recruited for this study (N = 28, 57.1% female, N = 24 White, N = 1 Black, N = 1 Hispanic, N = 1 Multiple Races). Body mass was measured (to the nearest 0.1 kg) with a calibrated digital scale (Tanita BWB-800, Tanita Corporation, Tokyo, Japan). Standing height was measured (to the nearest 0.1 cm) with a stadiometer (SECA 213, Seca Ltd., Hamburg, Germany). BMI was calculated by weight (kg) divided by height (m2). Three BMI-based equations were used to estimate BF%: Jackson (BMIJA), Deurenberg (BMIDE), Womersley and Durnin (BMIWD). A single digital image of each subject was taken from the rear/posterior view using a 12.9 inch, 64 g iPad Pro, and used to estimate BF%IMAGE. BF%3C included, body volume derived from underwater weighing, and total body water from bioimpedance spectroscopy (SFB7, Impedimed Ltd., Brisbane, AUS). A repeated measures ANOVA was performed to evaluate potential differences between BMIJA, BMIDE, BMIWD, BF%IMAGE, and BF%3C. An effect size (ES) was calculated, such that an overestimated BF% yielded a positive ES. Data are presented as mean ± standard deviation, with p < 0.05 used to determine statistical significance. Results: Body composition estimates ranged from 9.17 to 36.75 BF% (17.96 ± 5.92 BF%) as measured by BF%3C. Results from the ANOVA showed significant differences between BF% measures (p = 0.009). BMIJA (23.03 ± 5.62 BF%, ES = 0.86), BMIDE (22.44 ± 4.76 BF%, ES = 0.76), BMIWD (24.03 ± 4.70 BF%, ES = 1.02) produced significantly higher results than BF%3C (17.96 ± 5.92) (all p < 0.001). However, BF%IMAGE (17.20 ± 5.22 BF%) was comparable to BF%3C (ES = −0.13, p > 0.999). Conclusions: All BMI-based BF% equations significantly overestimated body composition when compared to BF%3C. BF%IMAGE produced results that were not significantly different than BF%3C, and indicate that BF% estimates derived from a single digital image provide a comparable measure of body composition in field settings. Current results are promising, however, this study should be replicated with a larger and more diverse sample. Practical Applications: Based on these preliminary data, body composition can be accurately measured using only a single 2-dimensional digital image. This novel approach could provide practitioners with an accurate method of estimating body composition when access to traditional laboratory methods is limited.

(65) Nutrition, Supplement, and Performance Enhancement Drug Practices OF In-Season Female Physique Competitors

J. Heredia, A. Khartabil, E. Ramirez, J. Mora, and G. Escalante

CSU, San Bernardino

INTRODUCTION: Female physique competitors (FPCs) utilize various nutrition, supplement, and performance enhancement drug (PED) practices to achieve low levels of body fat and maintain fat free mass (FFM) to succeed in their sport. Research in this area is scarce, particularly when it comes to FPCs. Purpose: To investigate the nutrition, supplement, and PED practices of in-season FPCs. Methods: Eight amateur female physique competitors (age 30.4 ± 3.6 years, height 160.31 ± 5.23 cm, weight 58.5 ± 6.7 kg) volunteered for this study. The subjects' height and weight were measured with a stadiometer and standard electric scale. Hydration levels were assessed with a refractometer by measuring the specific gravity of urine. Body composition was assessed with an A-mode ultrasound device (US) per the manufacturer recommended guidelines using the Jackson-Pollock 3 site formula to estimate body composition based on the body density prediction equation from the subcutaneous fat measurements of the triceps, suprailiac, and thigh. Subjects then answered specific questions about their nutrition, supplement, and PED practices over the last 30 days via a survey on Qualtrics.com. Results: Body fat percentage measures for the US were 13.9 ± 3.1%. A diet-recall 3 days prior to the competition revealed FPCs had an average daily intake of 226.8 ± 166 g protein, 47 ± 48 g fat, and 69 ± 64 g carbs. Daily water intake decreased gradually from 4.8 ± 2.6 L·d−1 3 days prior to competition down to 3.0 ± 2.6 L·d−1 one day prior to competition. The mean specific gravity of urine was 1.019 ± 0.01. The supplements used included caffeine (88%), thermogenic blends (88%), branched chain amino acids (75%), multi-vitamins (63%), glutamine (50%), whey protein (50%), vitamin C (38%), vitamin D (38%), essential amino acids (38%), Omega-3 (38%), casein protein (25%), zinc (13%), vitamin E (13%), vitamin B (13%), and other (13%). The PEDs used were testosterone propionate (13%), oxandrolone (13%), stanozolol (13%), and clenbuterol (13%). Other drugs used were diuretics (25%), tamoxifen (25%), and marijuana (13%). Conclusions: FPCs utilize several nutrition, supplement, and PED practices to prepare for competitions, but the evidence is scarce about their efficacy and safety. The large standard deviations on macronutrient and water intake indicate there is significant variability in the nutrition strategies used by competitors. Practical Applications: Future studies on FPCs are necessary to evaluate whether the current practices utilized are safe, effective, and efficient for them to succeed in their sport.

(66) Transcranial Direct Current Stimulation (TDCS) as an Aid to Esports Performance

C. Garner, R. Dykstra, B. Roth, T. Dundore, M. Miller, and N. Hanson

Western Michigan University

In recent years, organized, high-level video game competitions known as eSports (electronic sports) have grown increasingly popular. As eSports gaming expertise develops, it is imperative to understand the neurocognitive processes that would improve performance, for example, processing speed, stimulus detection, and stimulus interpretation. Previous research has suggested that transcranial direct current stimulation (tDCS) may be an effective method for improving various aspects of cognitive performance. However, preceding research is limited to healthy, non-gaming populations. Purpose: To assess whether the use of tDCS improves cognitive performance in eSports gamers. Methods: Subjects consisted of twenty-three healthy males (age 21.3 ± 3.2 years, BMI 25.6 ± 4.6 kg·m−2) who reported at least 5 hours of gaming per week for the preceding 3 months. All were asked to come to the lab for 2 visits; one experimental condition (∼2 mA of current) and one sham (no stimulation), the order of which was blinded and counterbalanced. All tDCS treatments were administered over the motor cortex for 20 minutes using the Halo Sport 2 headphones (Halo Neuroscience). Reaction time (RT) and response accuracy (RA) were assessed via the Stroop Color Word Task (SCWT) before and after the administration of tDCS. Reaction time and response accuracy data were grouped into 3 categories relating to the nature of the stimuli for analysis: control (CT), congruent (CG), and incongruent (ICG). 2 (condition: experimental & control) x 2 (time: pre & post) repeated measures ANOVAs were used to analyze the data. Results: For RT, there was a main effect of time for all 3 variables (CT, CG, & ICG; all p < 0.01); respondents had faster RT in the “post” stimulation measurement, regardless of tDCS condition. No differences in RT were found for tDCS condition. For RA, a main effect of condition (p = 0.018) for the CG variable was found. However, CG response accuracy was greater with the sham condition, not the experimental condition. Conclusions: This study suggests tDCS is not an effective method for enhancing reaction time or response accuracy in eSports gamers. Practical Applications: Future research should seek to determine whether physical fitness, cognitive capacity, or perception of the efficacy of tDCS has an effect on tDCS interventions. Additionally, future tDCS treatments should attempt to identify other focus points for stimulation that may result in enhancement of cognitive performance. Given that previous research has suggested tDCS as an effective intervention for aspects of cognitive performance, consideration of these attributes could provide insight into population or individual characteristics that suggest particular subjects to be more likely to benefit from tDCS.

(67) The Relative Contributions of Muscle Cross-Sectional Area, Muscle Quality, and Sex to the Prediction of Maximal Isometric Leg Extension Force

T. Neltner,1 J. Anders,1 J. Keller,2 K. Hergenrader,3 T. Housh,1 R. Schmidt,1 and G. Johnson3

1University of Nebraska-Lincoln;2University of South Alabama; and3University of Nebraska—Lincoln

Measurements of muscle cross-sectional area (mCSA) and muscle quality may provide information regarding the factors that contribute to the force production capabilities of a muscle. Purpose: The purpose of this study was to examine the relative contributions of mCSA, muscle quality, and sex to the prediction of maximal voluntary isometric contraction (MVIC) leg extension force. Methods: Thirty adults (15 males, 15 females; mean (±SD) = 20.2 ± 1.5 years) were assessed for mCSA and muscle quality based on echo intensity (EI) of the vastus lateralis of the right leg via ultrasound imaging and performed 2 bilateral MVICs. The MVIC force was measured at a knee joint angle of 120° (180° corresponding to full extension) using a load cell attached to the right leg lever arm of the isokinetic dynamometer. Zero-order correlations were used to determine the relationships among mCSA and EI, and MVIC force. Full-model and stepwise regression analyses were used to determine the relative contributions of mCSA, EI, and sex to MVIC force. Results: Mean (±SD) right leg extension MVIC force was 55.86 ± 14.79 kg and 39.28 ± 9.86 kg, for males and females, respectively. Zero-order correlations indicated that mCSA (r = 0.774, p < 0.001) and EI (r = −0.459, p = 0.011) were significantly correlated with MVIC force. Muscle CSA was also significantly correlated with EI (r = −0.663, p < 0.001). The stepwise regression model indicated that only mCSA significantly contributed to the prediction of MVIC force, and the full-model regression analysis indicated that mCSA was a 7 times more potent predictor of MVIC force than EI (Table 1). Conclusions: The current results were consistent with previous studies that have reported moderate to high coefficients of determination (r2 = 0.16–0.88) among mCSA, EI, and force. In the current study, mCSA and EI accounted for 60 and 21% of the variance in force production, respectively. Furthermore, the standardized coefficients from the full-model regression analysis indicated that mCSA was a 7 and 9 times more potent predictor of force than EI and sex, respectively. The stepwise regression analysis indicated that EI and sex did not contribute significantly to the explained variance in force, beyond that from mCSA alone. Thus, mCSA was the strongest predictor of isometric leg extension force regardless of sex. Practical Applications: The current findings suggested that resistance training programs aimed at improving isometric leg extension force in men and women should be designed to increase mCSA without concern for changes in muscle quality (as measured by EI).

Table 1 - Prediction of leg extension MVIC force (kg) from muscle CSA (cm2), echo intensity (AU) and sex using stepwise and full-model regression.

(9) Sex-Specific Muscle Activation During Fatiguing Tasks Anchored to Low and High Perceptual Based Loads

J. Keller,1 T. Housh,2 J. Anders,2 T. Neltner,2 R. Schmidt,2 and G. Johnson3

1University of South Alabama;2University of Nebraska-Lincoln; and3University of Nebraska—Lincoln

Performance fatigability (PF) is defined as the magnitude of change in maximal voluntary isometric contractions (MVIC) following a fatiguing task and 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 differences in muscle activation and force patterns of responses as well as PF resulting from sustained isometric muscle actions above and below critical force (CF). Methods: Twenty-four adults (12 men, 12 women) performed sustained, bilateral, isometric leg extension muscle actions anchored to RPE = 1 and 8 (10-point scale). MVICs were performed before (pretest) and after (posttest) the sustained muscle actions. Electromyographic (EMG) amplitude (AMP) was assessed from the vastus lateralis of each leg. EMG AMP and force values were normalized to the respective MVIC and were calculated every 5% of time to task completion (TTC). A 2 (Sex: Men, Women) × 2 (RPE: 1,8) × 2 (Test: Pretest, Posttest) mixed factorial ANOVA was used to examine absolute MVIC values (i.e., PF). Polynomial regression analyses were used to examine the EMG AMP and force vs. time relationships. Students' t-tests were used to test for differences between the right and left legs. Results: There was no difference (p > 0.05) in CF values between the men and women (14.5 ± 3.7% MVIC vs. 14.6 ± 2.4% MVIC, respectively). In addition, there were no differences (p > 0.05) between the right and left legs, thus values were collapsed across legs. For the absolute MVIC values, there were no significant interactions, but main effects for Sex (p < 0.001) and Time (p < 0.001). The pairwise comparisons (collapsed across Sex and RPE) indicated that pretest MVIC (47.7 ± 14.8 kg) was significantly (p < 0.001; d = 0.38) greater than posttest MVIC (42.3 ± 13.8 kg). The men (55.4 ± 12.2 kg) exhibited significantly (p < 0.001; d = 2.1; collapsed across Time and RPE) greater MVIC force than women (34.6 ± 7.2 kg). During each sustained muscle action, the men and women exhibited significant (p < 0.05), negative, quadratic force vs. time relationships (R = −0.958 to −0.977). The men exhibited plateaus in the decrease in force at ∼92% (RPE = 1) and ∼84% (RPE = 8) of TTC. During RPE = 1, the women exhibited a significant (p < 0.05), negative, quadratic EMG AMP vs. time relationship (R = −0.856). For RPE = 8, the men and women exhibited significant (p < 0.05), negative EMG AMP vs. time relationships, but the men displayed a quadratic model (R = −0.828), whereas the women displayed a linear model (r = −0.930). Conclusions: Typically, as a result sustained muscle actions anchored to forces below CF, women demonstrate a greater resistance to fatigue (i.e., less PF than men). The current findings, however, suggested that when anchored to an RPE, men and women demonstrated similar degrees of PF (11%; collapsed across Sex) above and below CF. During the sustained muscle actions, the men exhibited a plateau in the decrease in force, whereas the women continued to decrease force, which occurred concurrently with sex- and intensity-related differences in muscle activation (EMG AMP). Thus, the men and women likely utilized different motor unit activation strategies to maintain RPE = 1 and 8, but this did not result in PF differences. Practical Applications: These results contribute to the overall understanding RPE-based resistance exercise responses and suggest a need for sex-specific guidelines to potentially maximize neural adaptations.

(10) The Effects of a 7-Week Sprint vs. Nordic Training Intervention on the Modifiable Risk Factors of Hamstring Strain Injury and Performance

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

University of Salford

The effect of the Nordic hamstring exercises (NHE) or sprint training (ST), in an ecologically valid training program, on the modifiable risk factors of hamstring strain injuries (HSIs) and athletic performance has received limited attention. Purpose: The purpose of this study was to observe the effect of NHE or ST on the modifiable risk factors of HSIs and dynamic and isometric force-time characteristics. Methods: Thirty-eight collegiate athletes (age = 22 ± 2.6 years, height = 175.6 ± 6.6 cm; mass = 74.2 ± 15.2 kg) were randomly assigned to either NHE, ST or control group. All groups performed an identical resistance training program twice per week, including clean derivatives, back squat, reverse lunge and Romanian deadlift. The NHE and ST groups performed additional NHE or ST. Pre- and post-intervention testing included; bicep femoris fascicle length (BFL) collected using a 10 cm field of view ultrasound with images taken at the mid-point between ischial tuberosity and lateral epicondyle. Eccentric hamstring strength (EHS) was assessed by subjects performing 3 NHE repetitions on the Nordbord device, sampling at 50 Hz. Performance testing included countermovement jump (CMJ) and isometric mid-thigh pull (IMTP) performed on a Kistler force platform sampling at 1000 Hz. BFL was analyzed using ImageJ software and the following equation OFL+(h÷SIN(PA)), where OFL is the observed fascicle, h is the perpendicular distance between aponeurosis and BF end point and PA is the pennation angle. Peak EHS, CMJ height and IMTP peak force was analyzed using custom designed excel spreadsheets. RMANOVAs were used to determine training induced changes. Post-hoc testing with Bonferroni corrections and Hedge's g effect sizes were performed to determine the magnitude of differences. An a priori alpha level was set at p ≤ 0.05. Hedge's g effect sizes interpreted as trivial (≤0.19), small (0.20–0.59), moderate (0.60–1.19) and large (>1.20). Results: A significant group × time interaction was found for peak EHS (p < 0.001) (Figure 1). The NHE group had a significant, large increase (p < 0.001,g = 1.40), ST group had a significant and moderate increase (p < 0.001,g = 1.02), while the control group had a significant and small increase (p < 0.001,g = 0.44). A significant group x time interaction was also found for IMTP peak force (p = 0.009), with significant and small increases observed for the NHE and ST groups only (p < 0.001,g = 0.33–0.40). Contrastingly, BFL and CMJ Height had a non-significant group × time interaction (p > 0.05), however significant and small-moderate increases were observed for all training groups (p < 0.001,g = 0.38–0.87). Conclusions: Similar adaptive responses can be achieved from the supplementation of either NHE or ST, however, the NHE is more effective at increasing EHS than ST. Practical Applications: Multiple methods (NHE & ST) could be used by practitioners to improve the modifiable risk factors of HSIs, while being effectively employed in an ecologically valid training program.

F10
Figure 1.:
Pre-to post intervention individual (black) and mean (red) changes in peak eccentric hamstring strength for the nordic, sprint and control groups.

(12) Quantifying Effort in Collegiate Football Players During Practice: Do Coaches Need Heart Rate Monitors?

V. Smith,1 T. Hew-Butler,2 W. Moore,2 R. Mendoza,2 C. Vargo,2 M. Schoen,3 L. Jimenez,2 J. Sabou,2 and M. Vansumeren2

1Wayne State Universiy;2Wayne State University; and3Cornell University

Heart rate (HR) monitors are gaining popularity as a useful tool for strength and conditioning coaches (SCC) to monitor athletes' “internal” (stress) loads in real-time. Quantifiable assessment of internal load may help SCCs make acute adjustments to workouts which maximize performance while enhancing recovery. Traditionally, rating of perceived exertion (RPE) has been a validated, cost-effective measure of physical effort. Purpose: To evaluate relationships between athletes reported and SCCs' perceived RPE vs. HR measures of effort in collegiate American football players during pre-season practice. Methods: During 6 pre-season practices, 29 NCAA DII male athletes' (age = 19.83 ± 1.65 years; body mass index = 33.45 ± 6.04 kg·m−2; weight = 116.55 ± 21.11 kg) were pre-assigned chest strap HR monitors they wore for the duration of each practice. Throughout practice a software system collected continuous percent of HRmax (%HRmax), training impulse (TRIMP), and percent of heart rate reserve (%HRR); these were visible to researchers only. At the conclusion of each practice athletes reported practice session rating of perceived exertion (sRPE) on a Borg CR-10 scale from 0 (nothing at all) to 10 (maximal). Additionally, one SCC reported observational sRPE for each athlete on the same scale. Results: Correlations across the 6 days were averaged to examine the general pattern of relationships. Athletes reported sRPE was negatively correlated with SCCs' perception of athletes' RPE (r = −0.21, range: −0.49 to 0.19). Athletes' reported RPE was correlated with each of the physiological measures: %HRmax (r = 0.34, range: 0.14–0.55), %HRR (r = 0.22, range: 0.12–0.33) and TRIMP (r = 0.37, range: 0.11–0.57). SCCs' perceived RPE was correlated with each of the physiological measures: %HRmax (r = −0.09, range: −0.26 to 0.36), %HRR (r = 0.03, range: −0.30 to 0.23) and TRIMP (r = −0.05, range: −0.33 to 0.17). TRIMP was strongly correlated with %HRRmax (r = 0.94, range: 0.78–0.99) and %HRR (r = 0.71, range: 0.62–0.85). The 29 athletes were then subdivided into linemen (n = 21) and non-linemen (n = 8) position groups (Table). On Days 5 and 6, linemen's sRPE was significantly (p < 0.05) lower than their %HRmax compared to non-linemen. Athletes' sRPE best correlated with TRIMP. Overall, there was high variability in the correlations between SCC RPE and physiological measures for both groups. Conclusions: SCCs' and athletes' sRPE poorly related to physiological measures. This is exacerbated among the lineman whose positions are more anaerobic in nature. HR is a good assessment of internal load during football practice. Practical Applications: Athletes need more education on accurately reporting their sRPE, especially if it is to be used to adjust training intensity. SCCs perceptions of athletes' load could also be better informed by capturing heart rate during practices (self-measure or monitor). HR monitors and informed self-report can be useful for understanding athletes' internal load.

Table 1 - Lineman and non-lineman correlations.

(1) Does Aerobic Fitness Contribute to Total Repetitions and Volume Load Performed During Intense Resistance Training?

C. Watts,1 E. Bass,1 B. Oddi,2 and A. Flatt1

1Georgia Southern University; and2California University of Pennsylvania

Acute resistance training (RT) performance is primarily fueled by anaerobic metabolism, but inter-set recovery is facilitated by aerobic processes. Thus, resistance-trained individuals with greater aerobic fitness may accumulate more volume during a standardized RT session relative to less-fit individuals. Purpose: We aimed to investigate potential associations between markers of aerobic fitness, total repetitions and total volume load performed during an intense bout of RT. Methods: Eleven males (25 ± 5 years; 178 ± 5 cm; 89 ± 12 kg) with at least 1 year of RT experience (10 repetition maximum barbell squat = 94.7 ± 12.7 kg) performed a graded maximal exercise test on a treadmill for the determination of maximal oxygen consumption (V̇o2max) and time-to-exhaustion (TTE). On a separate occasion, subjects performed 6 sets to momentary muscular failure in the barbell back squat, bench press and latissimus dorsi pull-down with loads corresponding to 90% of their 10 repetition maximum. Inter-set and inter-exercise rest periods were 90 and 120 seconds, respectively. Number of repetitions were recorded during each exercise and summed to determine total repetitions. Volume load was calculated for each exercise (volume load = repetitions × resistance) and summed to determine total volume load. Associations between variables were quantified with Pearson's correlations. Results: Mean and standard deviation for V̇o2max and TTE were 43.3 ± 6.6 ml·kg·min−1 and 704.3 ± 212.4 seconds, respectively. Subjects performed 226.4 ± 26.0 repetitions and accumulated 11,070.0 ± 1,464.0 kg of total volume load. V̇o2max was not associated with total repetitions (r = −0.14, p = 0.68) or total volume load (r = 0.08, p = 0.81). Similarly, TTE was not associated with total repetitions (r = −0.19, p = 0.58) or total volume load (r = 0.04, p = 0.91). Large, but non-significant associations between fitness parameters and volume load for the squat only were observed (r = 0.52–0.55, p = 0.08–0.10). Conclusions: Though non-significant, the large association between fitness parameters and squat volume load suggest that aerobic fitness derived from a treadmill test explains ∼25% of the variance in lower-body RT capacity in trained men. Practical Applications: RT volume load is a main driver of muscular strength and hypertrophy adaptations. These data suggest that segment-specific aerobic fitness (e.g., lower body) may partly contribute to lower-body work capacity during a standardized RT protocol, possibly by facilitating greater inter-set recovery.

(2) The Influence of Fatigue on the Intrasession Reliability of Performance Indices Following a High-Volume Back Squat Protocol

D. Tolusso,1 W. Dobbs,2 M. Esco,3 and S. Arnett1

1Western Kentucky University;2University of Wisconsin-La Crosse; and3The University of Alabama

A metric used to monitor individuals during a training program must be reliable, sensitive, and quickly administered. However, random variability will have a negative impact on measurement reliability and sensitivity. Fatigue increases this random variability in the form of movement and neuromuscular variability. While the reliability of monitoring tools has been assessed previously, it has generally been done in non-fatigued individuals. However, individuals will experience a continuum of fatigue over the course of a training cycle. It may be that this increased biological variability due to fatigue is deleterious to the reliability and sensitivity of popular tools used to assess recovery. Purpose: The purpose of this study was to evaluate the impact that fatigue had on the reliability of tools designed to monitor recovery during training. Methods: Eleven healthy, resistance trained men were recruited for the study. The first testing session consisted of performance tests followed by fatiguing back squat protocol. Performance tests consisted of 3 countermovement jumps (CMJ) separated by 1-minute of recovery between each attempt and 2 back squats at 70% 1RM with 3-minutes of recovery between each attempt. The fatiguing protocol consisted of 8 sets of 10 back squats at 70%1RM with 2-minute of recovery between sets. Individuals returned to the laboratory 24, 48, and 72 hours after the protocol to complete the performance tests again. Raw CMJ height and mean bar velocity (MBV) within each day were recorded for use in later analyses. To account for between subject variability in fatigue trends following the back squat protocol, subjects daily performance was reclassified as a fatigue status (FS). Briefly, recovery scores for CMJ and MBV were calculated and averaged to compute a daily recovery score for each individual. The highest daily recovery score (i.e., lowest fatigue state) was denoted as FS1 and lowest daily recovery score was denoted as FS4. Two-way, mixed effect intraclass correlation coefficients (ICC) were used as a measure of relative reliability. Standard error of the measurement (SEM) was utilized as a measure of intrasession absolute reliability. Results: Lower bound ICC values for both metrics were high, indicating moderate to good reliability with no apparent trend involving FS. There was one instance where the lower bound ICC value for MBV indicated low reliability, but this could have been an artifact of low between-subject variability. However, SEM values for both CMJ and MBV were lower in FS1 to FS4, indicating a role of fatigue on reliability (Figure 1). Conclusions: The current findings suggest that fatigue negatively affects the intrasession reliability of CMJ and MBV. Practical Applications: It is suggested that practitioners take the average of multiple CMJ and MBV attempts within a session. This will allow for a more stable and sensitive metric for comparisons, but at the cost of increased time for the additional attempts.

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Figure 1.:
The relationship between fatigue status and standard error of the measurement for countermovement jump height and mean bar velocity.

(03) An Acute Bout of Resistance Exercise Increases Skeletal Muscle Oxygen Extraction Rate in the Postprandial Period

H. Bryan, E. Roger, N. Banks, and N. Jenkins

Oklahoma State University

Purpose: To examine the effects of an acute bout of resistance exercise the night prior to a high-fat meal (HFM) on non-invasive measurements of oxygen consumption rate and microvascular reactivity in the postprandial period in younger and older males. Methods: Eight younger males (age = 24.3 ± 3.5) and 6 older males (age = 60.8 ± 5.1) completed 2 conditions, resistance exercise (RE) or control (CON), which consisted of passive rest, the night prior to consuming a standardized HFM (12 kcal·kg−1 bodyweight; 63% fat). Prior to, and 1-, 3-, and 5-hour after consuming the HFM, skeletal muscle oxygen extraction/utilization and microvascular function were assessed using the near-infrared spectroscopy with vascular occlusion test (NIRS-VOT). During the NIRS-VOT, tissue saturation (StO2) was monitored, and the rate of decrease in StO2 (Slope 1) and minimum tissue saturation (StO2min) achieved during cuff inflation were quantified, as were the reperfusion magnitude (Repmag), the rate of increase in StO2 (Slope 2), and the reperfusion area under the curve (StO2auc) following cuff deflation. Two-way (condition × time) ANOVAs were used to examine each of the dependent variables. Results: There were significant condition × time interactions for Slope 1 (p = 0.03) and StO2min (p = 0.048). Follow-up analyses indicated that Slope 1 became steeper (e.g., decreased) from baseline to 3-h (−0.03 ± 0.02%·s−1, p = 0.01), before increasing back to baseline values from 3- to 5-h (+0.03 ± 0.03%·s−1, p = 0.05). There were no significant change (p = 0.0X) in Slope 1 across time in the CON condition. Consequently, slope 1 was more negative in RE than CON at 1-hour (p = 0.009), but not at 3-hour (p = 0.07) or 5-hour (p = 0.15). StO2min decreased from baseline to 1- (p = 0.01) and 3-hour (p = 0.03), and then increased back to baseline levels from 3- to 5-hour (p = 0.026) in the RE condition. There were no changes in StO2min across time (p = 0.88) in the CON condition. Consequently, the StO2min achieved was lower during RE than CON at 1-hour (p = 0.018). There were no significant condition × time interactions or main effects for Repmag, Slope 2, or StO2auc (all p > 0.05). Conclusions: Overall, these results show that an acute bout of resistance exercise increases skeletal muscle oxygen consumption and/or extraction rate in the postprandial period. However, it did not influence microvascular reactivity, as assessed using the NIRS-VOT technique. Practical Applications: It has previously been suggested that postprandial lipemia causes an impairment in blood-tissue oxygen transport. Although we did not observe HFM-induced changes in Slope 1 or StO2min in the postprandial period in our sample, we did see a steepening of Slope 1 and a reduction in StO2min in the RE condition following the HFM. Thus, RE the night prior to a HFM improves peripheral oxygen extraction and/or consumption rate in the postprandial period. Additional studies are needed to examine the utility of RE for improving oxygen extraction and microvascular reactivity in populations who have peripheral physiological derangements that result in lower oxygen extraction, such as those with heart failure with preserved ejection fraction (HFpEF).

(4) A Preliminary Investigation Into the Validity of a Submaximal Protocol to Predict One Repetition Maximum (1-RM) in the Back Squat

D. Bishop,1 H. Dorrell,1 S. Dias,1 S. Thompson,2 and J. Moore3

1University of Lincoln;2Sheffield Hallam University; and3University of Portsmouth

Purpose: To assess the validity of a submaximal protocol designed to predict the one repetition maximum (1-RM) in the free-weight back squat. Undertaking a 1-RM carries a risk of injury due to the maximal nature of the assessment, however, if a protocol and equipment can be used to accurately predict an individual's strength through a submaximal assessment then this will negate the need to take athletes to maximal levels. Methods: Fifteen resistance trained individuals (mean ± SD, stature: 178.0 ± 6 cm, body mass: 85.0 ± 11.3 kg 1-RM: 148.5 kg), were recruited. Subjects completed 2 visits, the first a habituation of the protocol and the second, testing of a submaximal predication of 1-RM using the Flex laser optic device. The Flex software sets a series of progressive incremental loads based on a subject's estimated 1-RM. At each load, the device captures concentric movement displacement and time, enabling the calculation of mean concentric velocity (MCV). Linear regression is then applied to the captured data between absolute load and attained MCV, facilitating the prediction of 1-RM. Following the Flex prediction, subjects were blinded to the result and a standardised 1-RM protocol was followed, loading the bar in increments until the subject could no longer complete an unaided repetition. For all repetitions, subjects were instructed to maintain eccentric control before completing the concentric phase as explosively as possible. Least products regression (LPR) were used to assess linearity and proportional bias, enabling quantification of validity between the 2 measures. Systematic and random error of the Flex were assessed by quantifying the 95% limits of agreement (LOA) between predicted and actual 1-RM data. Results: Back squat mean and standard deviation for the predictive and actual 1-RM was 166.9 ± 52.1 kg and 1-RM was 148.5 ± 46.1 kg, respectively. LOA from −21 to 52 kg indicate that on average the Flex submaximal protocol has a systematic error over predicting an individual's 1-RM by 15.5 kg, with a random error of 36.8 kg. Whilst the LPR between the predicted and actual measures resulted in an R2 ≥ 0.89 demonstrating a degree of similarity in the 2 values, the intercept, y = 16.01+(0.81*x) demonstrates that there appears to be proportional bias that is, as strength increases the error also increases. Conclusions: The preliminary findings suggest that whilst there is a degree of correlation between the Flex predicted value and actual 1-RM, it does not provide a sufficiently valid measure of 1-RM strength for the free-weight back squat in trained individuals, generally over predicting 1-RM values. In addition, the random bias of the device increases in proportion to maximal strength. The sample size of 15 subjects in the current study was small and therefore there is a need for further research using a larger subject pool in addition to the examination of the validity for the deadlift and bench-press lifts before full conclusions are drawn. Practical Applications: At present, practitioners wanting to examine maximal strength levels for the free-weight back squat should continue to use conventional 1-RM protocols.

(5) Mean Force, Power, and Velocity Responses to Rest Redistribution With Heavier Loads for the Squat Exercise

S. Chae, S. McMullen, S. Moses, C. Bailey, D. Hill, and J. Vingren

University of North Texas

When using the same resistance exercise load, rest redistribution (RR) that incorporates intra-set rest results in greater force, power, and velocity compared with traditional set (TS). RR may allow for heavier loads during exercise, but, no study has directly compared RR combined with a heavier load to TS. Purpose: The purpose of this study was to investigate the effect of RR combined with heavier loads (RR + L) on mean force, power, and velocity in resistance trained-men. Methods: 10 resistance-trained men (mean ± SD; 23.3 ± 4.6 years; 175.6 ± 6.3 cm; 77.7 ± 10.8 kg; 4 ± 3 years training) completed 3 sessions, each of which were separated by at least 3 days. One-repetition maximum (1RM) back squat (BS) (138.7 ± 30.2 kg), and 1RM BS:body mass (1.8 ± 0.2) were determined in Session 1. For Session 2 and 3, subjects were randomly assigned to either RR + L (3 sets of (2 × 5 reps) with 30 seconds (s) intra-set rest and 90 seconds inter-set rest using 75% 1RM BS) or TS (3 sets of 10 reps with 120 seconds inter-set rest using 70% 1RM BS). Subjects were instructed to perform every repetition “as explosively as possible.” Mean force (x̄F), power (x̄P), and velocity (x̄V) were collected for each repetition by a linear position transducer (GymAware Power Tool, Kinetic Performance Technologies, Canberra, Australia). Data were analyzed using two-way ANOVAs with repeated measures. Results: A condition by repetition (p < 0.05) interaction was observed for x̄F and x̄V. x̄F was significantly greater in RR + L compared with TS for repetition 1 to 10 during set 3 (p < 0.01). x̄V was significantly greater in TS compared with RR + L for repetition 1 to 5 during set 2 and for repetition 1 to 6 during set 3 (p < 0.05). A main effect of condition (p < 0.05) interaction was also observed for x̄F and x̄V. When averaged across 10 repetitions, x̄F was significantly greater (p < 0.01) in RR + L compared with TS during set 1 (1856.03 ± 104.28 vs. 1791.21 ± 99.82 N), set 2 (1733.56 ± 108.02 vs. 1,673.22 ± 103.72), and set 3 (1815.95 ± 98.38 vs. 1745.37 vs. 91.31). x̄V was significantly greater (p < 0.05) in TS compared with RR + L during set 2 (0.50 ± 0.02 vs. 0.46 ± 0.02 m·s−1) and set 3 (0.47 ± 0.03 vs. 0.42 ± 0.02). Conclusions: RR + L resulted in greater x̄F compared with TS likely due to the greater loads. RR + L had similar x̄V to TS during the last repetitions despite the greater loads. Practical Applications: Despite heavier squat exercise loads, 30 seconds intra-set rest allowed for greater force while maintaining velocity during the last repetitions compared with TS. Thus, coaches could consider incorporating short intra-set rests as it allows for additional loads, and thus increased force while largely maintaining velocity for the squat exercise.

(6) Eccentric Utilization Ratio in Collegiate Baseball Athletes: Theory and Application

B. Guthrie,1 C. Haun,2 M. Jones,1 C. Bellon,3 and C. Williams4

1George Mason University;2LaGrange College;3The Citadel; and4University of North Florida

The eccentric utilization ratio (EUR) provides information on stretch shortening cycle performance in explosive movements, and can provide insight on neuromuscular adaptation across training phases. Purpose: To develop a theoretical framework for analysis and interpretation of EUR relative to training phase. Methods: National Collegiate Athletic Association Division III baseball athletes (n = 24) participated as part of their 10-week periodized, off-season strength and conditioning program. Squat jumps (SJ) and countermovement jumps (CMJ) were evaluated via jump contact mats. EUR was calculated from jump height (JH, inches) and peak power (PP, Watts) with the equations: EURJH = CMJJH/SJJH and EURPP = CMJPP/SJPP. Testing sessions began with a supervised dynamic warm-up followed by 3 familiarization trials per jump. For SJ, the same trained tester visually estimated the starting point of 90° knee flexion for each subject. Next, athletes jumped with maximal effort straight up with no downward movement. The CMJ began from a tall standing position followed by a rapid downward action followed by a maximal effort jump. All jumps began on the cadence of “3,2,1, JUMP!”. Athletes were instructed to be explosive and jump as high as they could for each trial. Hands remained on the hips and a controlled landing was expected. Two maximal effort trials for SJ and CMJ were recorded with a third, if the first 2 did not fall within ±0.1 in of each other. Descriptive statistics (mean ± SD) were calculated for performance variables, and T-tests were utilized to examine differences in pre- and post-test measures (p < 0.05). Pearson product-moment correlations were used to evaluate relationships between variables. Results: Increases in CMJPP (121.47 W ± 214.57 W, p = 0.01) and SJPP (152.52 W ± 210.58 W, p = 0.002) occurred over the training period. There were no increases in CMJJH. The SJJH trended upwards (p = 0.08). Further, the EURJH (p = 0.42) and EURPP (p = 0.49) remained unchanged. There was a negative relationship between EURJH and SJJH (r = −0.592, p = 0.002). EURPP was positively related to CMJPP (r = 0.440, p = 0.03) and negatively related to SJPP (r = −0.531, p = 0.01). A schematic figure that represents changes in EUR, SJ, and CMJ based upon findings of the current study (i.e., striped bar) and previous research (i.e., gray bar) across training phases is depicted in Figure 1. Conclusions: These data support previous findings and the theory that EUR is sensitive to training phase. In this study, athletes showed decreases in EUR over their 10-week program, which emphasized muscular strength and size, relative to changes in vertical jump performance. Practical Applications: EUR is a simple and cost-effective measure that is sensitive to training phase. Relative to changes in vertical jump, EUR can assist in comparing desired to actual training outcomes specific to the demands of the sport and thus, can be used as part of a comprehensive monitoring program.

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Figure 1.:
Theoretical annual EUR outcomes. GPP, general preparation phase; SPP, specific preparation phase; Pre, pre-competitive phase; Comp, competitive phase; Post, post-competitive phase; SE, strength endurance; EUR, eccentric utilization ratio; CMJ, countermovement jump; SJ, squat jump.

(7) Physical Fitness and Anthropometric Correlates for Three Baseball Skill Drills in 32 Male Division II Baseball Players

A. Williams, A. Thompson, and J. Keeler

Kentucky State University

Baseball specific skill and performance is difficult to determine, however common baseball skill drills (BBSD) have been widely used to predict potential in baseball athletes. Some common BBSD include the maximum throwing distance, the 60-yard dash, and more recently exit hitting velocity. Previous research has demonstrated that these BBSD can be improved through traditional strength and power training regimes, but no study to the researchers' knowledge has identified predictors of aforementioned BBSD in NCAA division II baseball players. Purpose: To identify physical fitness and anthropometric correlates and predictors for 3 baseball skill drills including max throwing distance, 60-yard dash, and hitting exit velocity. Methods: Retrospective analysis was performed on 32 male division II baseball players' preseason data. Subjects completed physical fitness (max squat: 254.7 ± 52.9 lbs, max deadlift: 352.4 ± 57.1 lbs, max repetition chin ups: 9.1 ± 5.5, broad jump: 92.0 ± 9.1 in) and anthropometric measures (age: 19.8 ± 1.4 years, height: 72.5 ± 2.8 in, weight: 189.8 ± 35.9 lbs, body mass index (BMI): 25.4 ± 4.3) prior to completing 3 BBSD, including the 60-yard dash, exit hitting velocity (off a tee), and max distance throw. Pearson product moment correlations and multiple linear regression were used to identify correlates of each BBSD. Significance set at p < 0.05. Results: The broad jump and BMI together served as the best predictors for the 60 yard dash (adj. R2 = 0.72, p < 0.001). The deadlift was the only predictor of hitting exit velocity, but only explained 23% of the variance (adj. R2 = 0.24, p = 0.02). No significant variance could be explained for max distance throw, but its highest correlate was the broad jump (r = 0.35). Conclusions: The purpose of this investigation was to determine predictors of performance on 3 BBSD. This investigation found that lower body power (broad jump) and BMI were the best predictors of performance on the 60-yard dash. The max deadlift almost explained a quarter of the variance in the hitting exit velocity, which means lower leg strength might play a key role in that drill. However for the max distance throw there was little correlation among the physical fitness tests performed. Future studies could use large sample size and a broader range of fitness testing to determine better predictors of all 3 BBSD. Practical Applications: Baseball coaches and strength coaches working with baseball athletes should focus on lower body power exercises to improve 60-yard dash performance.

(8) Effect of the Repetition-In-Reserve Resistance Training Strategy on Total Work Completed, Perception of Effort, and Muscle Damage in Well-Trained Men

N. Velazquez,1 P. Serafini,1 M. Stratton,2 A. Olmos,1 M. Lee,1 T. VanDusseldorp,1 Y. Feito,1 and G. Mangine1

1Kennesaw State University; and2Texas Tech University

Maximizing training volume has been used as a resistance training strategy for individuals training for muscle hypertrophy. One method for increasing volume is to take sets to failure. However, this may lead to excessive fatigue and damage that could negatively impact subsequent exercises and workouts. The repetitions-in-reserve (RIR) strategy may help minimize the amount of damage sustained while still allowing the trainee to achieve sufficient or greater volume for stimulating hypertrophy. Currently, there is little scientific evidence to support the use of the RIR training strategy. Purpose: To compare the effects of RIR vs. sets to failure during an acute bout of bench press on total work completed, perception of effort, and damage in well-trained males. Methods: Fourteen males (24.6 ± 3.0 years, 176 ± 5 cm, 85.7 ± 14.0 kg) with resistance training experience (>3 years), who have participated in regular resistance training (≥3 sessions per week) for more than one year and qualified as class III athletes for the bench press under United States Power Lifting Association guidelines, volunteered for this crossover-design study. Following an initial assessment of one-repetition maximum (1RM) in the bench press and a familiarization of one set to failure at 80% of 1RM on their first visit (V1), subjects were randomly assigned to complete 5 sets at 80% of 1RM using one of 2 repetition conditions (3-RIR: 4 sets to 3 repetitions-in-reserve and a final set to failure; or 0-RIR: all sets to failure) on the next visit (V2). Ratings of perceived exertion (RPE) were collected following each set, while blood samples were collected prior to and following activity on V2, as well as at 24-, 48-, and 72-hrs post-exercise (V3 − V5). After one week, subjects completed the opposite repetition condition (visit 6; V6) and returned for blood sampling on visits 7 − 9 (V7 − V9). Blood samples were analyzed for concentrations of creatine kinase (CK). Results: Two-way (condition x time) analysis of variance with repeated measures indicated significant (p < 0.001) interactions for total work completed and RPE. Across all sets, 3-RIR reported lower RPE (8.2 ± 1.2) and completed more work (8,708 ± 1751 J) compared to 0-RIR (RPE = 10 ± 0; Total work = 8,249 ± 1655 J). Although post-exercise CK concentrations increased from pre-exercise by 40.8 ± 66.0%, and remained elevated (14.8–66.1%) over the following 72 hours for 0-RIR, these were not statistically (p = 0.430) different from 3-RIR (post-exercise = 32.2 ± 55.3%; 24–72-hours post-exercise = −7.2 to 20.3%). Conclusions: The 3-RIR strategy with one final set to failure enabled resistance-trained men to perform more work at a lower perceived effort while producing comparable damage in comparison to performing 5 sets to failure. Practical Applications: Coaches and athletes wishing to use resistance training to build muscle might utilize the repetitions-in-reserve method to increase the total amount of work performed on specific exercises while also subjectively reducing perceived effort and without increasing fatigue and damage. Over time, this strategy may facilitate work completed over training and potentially elicit greater hypertrophy.

(9) Peak Force, Power, and Velocity Responses to Rest Redistribution With Heavier Loads for the Squat Exercise

S. McMullen, S. Chae, S. Moses, C. Bailey, D. Hill, and J. Vingren

University of North Texas

Rest Redistribution (RR) with intra-set rest and similar loading parameters has shown an increase in force, power, and velocity when compared to traditional sets (TS) potentially allowing an increased load to be utilized if repetitions remain constant. No studies have been conducted comparing RR with heavier loads to TS using the same rep/set protocol. Purpose: The purpose of this study was to investigate the effect of RR combined with heavier loads (RR + L) on peak force, power, and velocity in resistance trained-men. Methods: Ten resistance-trained men (mean ± SD; 23.3 ± 4.6 years; 175.6 ± 6.3 cm; 77.7 ± 10.8 kg; 4 ± 3 years training) completed 3 sessions, each of which were separated by at least 3 days. One-repetition maximum (1RM) back squat (BS) (138.7 ± 30.2 kg), and 1RM BS:body mass (1.8 ± 0.2) were determined in Session 1. For Session 2 and 3, subjects were randomly assigned to either RR + L (3 sets of (2 × 5 reps) with 30 seconds (s) intra-set rest and 90 seconds inter-set rest using 75% 1RM BS) or TS (3 sets of 10 reps with 120 seconds inter-set rest using 70% 1RM BS). Subjects were instructed to perform every repetition “as explosively as possible.” Peak force (PF), power (PP), and velocity (PV) were collected for each repetition by a linear position transducer (GymAware Power Tool, Kinetic Performance Technologies, Canberra, Australia). Data were analyzed using two-way ANOVAs with repeated measures. Results: A main effect of condition (p < 0.01) was observed for PF. When averaged across 10 repetitions, PF was significantly greater (p < 0.01) in RR + L than TS during set 1 (2,458.42 ± 173.65 vs. 2,394.66 ± 168.30 N). No main effect of condition for PF was observed during set 2 and 3. No main effect of condition was observed for PP and PV. No main effect of condition by repetition was observed for PF, PP, and PV. Conclusions: RR + L resulted in greater PF than TS during the first set likely due to the greater loads. Both RR + L and TS showed losses in PP and PV across sets regardless of exercise loads. Practical Applications: RR + L with 30 seconds intra-set rest allowed for the use of heavier loads resulting in greater force while maintaining velocity compared with TS. Further longitudinal studies should be conducted to measure long-term potential power adaptations using RR + L compared with TS.

(10) Electromyographical Analysis of the Landmine Squat in College-Aged Men and Women

K. Collins, B. Christensen, L. Klawitter, R. Waldera, and S. Mahoney

North Dakota State University

Introduction: The squat is a commonly used exercise in a variety of settings and is central to many resistance training programs. The landmine squat (LS) is a variation where one end of the barbell is anchored to the floor and the other is held in front of the lifter. The arced bar path moving down and back into the lifter could encourage heel contact and good posture, and maintain a certain amount of mass anteriorly while pushing the lifter into a more hip dominant position. This position can reduce torque on the knee and be well suited for learning squat progressions or rehabilitation purposes. Little research exists on the LS, and eliciting muscle activation differences between men and women is of importance for proper exercise prescription. Purpose: To investigate the electromyographic (EMG) characteristics of the LS and differences between college-aged men and women. Methods: This study included 16 men and 16 women (age: 22 ± 3 years, height: 1.73 ± 0.09 m, body mass: 75.94 ± 12.44 kg). Surface EMG electrodes were placed on the vastus medialis (VM), vastus lateralis (VL), semitendinosus (ST), and biceps femoris (BF) muscles in accordance with SENIAM guidelines, with an inter-electrode distance of 2 cm. EMG signals were band pass filtered at 10–500 Hz and smoothed using RMS with a 50-millisecond window. Maximal voluntary isometric contractions (MVIC) were performed with seated knee extension and prone knee flexion against manual resistance. Peak values were obtained from 2, 5 seconds (s) attempts for each MVIC position. Subjects completed 5 repetitions (2-s eccentric; 2-s concentric) of the LS with the load set to 30% (rounded to nearest 5 lbs.) of their body mass. Peak signal of all 5 repetitions were averaged and normalized as percent MVIC (%MVIC) for each muscle. Ratios were calculated using the average %MVIC values for hamstring to quadricep (ST:VM and BF:VL) and medial to lateral quadricep (VM:VL). Results: One-way analyses of variance (p < 0.05) revealed significant differences; women produced higher %MVIC activity in the VM (30% more, F = 9.62, p = 0.004), VL (27% more, F = 4.66, p = 0.039), and ST (5% more, F = 4.93, p = 0.034) muscles. Men produced slightly higher BF and BF:VL ratio, but the level did not reach statistical significance. No significant differences were found between the other ratios. Conclusions: Women displayed greater quadricep activation than men during the LS, which may indicate quadricep dominance. However, the lack of difference in the hamstring to quadricep ratios (ST:VM, BF:VL) or the VM:VL ratio points toward no discernible difference in muscle activation between men and women. Additionally, women displayed higher activation of the medial hamstring (ST) musculature which evens out the increased quadricep activation and is positive for increasing hamstring strength along with the quadriceps. The LS appears to illicit a balanced muscle activation response in terms of the medial to lateral quadricep ratio, and the 2 hamstring to quadricep ratios despite the overall difference between men and women. Practical Applications: The differences in quadricep and medial hamstring activation between men and women should be taken under advisement while programming the LS squat for training. The LS should be included with other exercises that promote hamstring activation along with the quadriceps, especially for injury prevention or rehabilitation purposes.

(11) Maximal Eccentric Exercise Induces Greater Decreases in Strength and Greater Soreness Compared to Concentric and Submaximal Eccentric Exercise

A. Brannon,1 R. Colquhoun,1 M. Magrini,2 S. Fleming,1 N. Banks,3 E. Rogers,3 and N. Jenkins3

1University of South Alabama;2Creighton University; and3Oklahoma State University

Purpose: The purpose of this study was to examine the time-course of changes in maximal strength and soreness following maximal eccentric, maximal concentric, and concentric work-matched eccentric exercise of the elbow flexors. Methods: Eighteen strength-trained males (mean ± SD; age = 24 ± 3 years) completed 6 sets of 10 repetitions of maximal eccentric (ECC), maximal concentric (CON) and concentric work-matched eccentric (ECCWM) contractions of the elbow flexor muscles through a ∼90° range of motion. The order of conditions and arm utilized was quasi-randomized for each subject and 2 minutes of rest were given between each set. For all testing, subjects were seated in an isokinetic dynamometer, with force recorded from a load cell attached to a custom-built handle secured on the arm of the dynamometer. Maximal voluntary isometric contraction (MVIC) strength was recorded prior to (PRE), as well as immediately (POST), 1-hour (POST1), and 48-hours (POST48) post-exercise. Muscle soreness (DOMS) of the biceps brachii, via a visual analog scale, was measured at PRE, POST1, and POST48. All visits took place at the same time of day (±1 hour) and all exercise conditions were separated by 6 ± 1 day. MVIC strength was calculated offline using custom-written LabView software. All statistical analyses were run in SPSS (v. 23, IBM, Inc., Armonk, NY, USA) with an a priori Type I error rate of 5%. Results: Repeated measures ANOVAs indicated significant Condition × Time interactions for both MVIC (p < 0.001) and DOMS (p < 0.001). Post-hoc one-way ANOVAs indicated that MVIC was significantly different at all time points in the ECC condition (PRE: 43.1 ± 10.1 kg; POST: 25.2 ± 10.9 kg; POST1: 28.9 ± 10.6 kg; POST48: 36.3 ± 10.8 kg; p < 0.001–0.012). In the CON condition, MVIC was significantly greater at PRE (43.6 ± 7.7 kg) when compared to POST (32.7 ± 9.0 kg; < 0.001) and POST1 (37.1 ± 9.1 kg; p = 0.003), but not POST48 (42.7 ± 8.8 kg; p > 0.99). CON POST MVIC was significantly less than POST1 (p = 0.003) and POST48 (p < 0.001), and CON POST48 MVIC was significantly greater than POST1 (p = 0.002). In the ECCWM condition, MVIC was greater at PRE (44.9 ± 7.9 kg) than POST (36.8 ± 6.9 kg) and POST1 (38.3 ± 7.2 kg; p < 0.001 for both), but not POST48 (43.4 ± 8.0 kg; p = 0.731). Analyses also revealed significantly greater MVIC at POST48 when compared to POST and POST1 in the ECCWM condition (p < 0.001 for both). No significant differences in MVIC were observed at PRE across conditions (p = 0.395–0.99). ECC MVIC was significantly lower than both CON and ECCWM at POST, POST1 and POST48 (p ≤ 0.001–0.002). POST CON MVIC was significantly lower than POST ECCWM MVIC (p = 0.031), but no differences were observed at POST1 or POST48 (p > 0.99 for both) between CON and ECCWM. Post-hoc analyses also revealed significantly greater DOMS at POST48 ECC (3.2 ± 1.9 au) than at PRE in all conditions (0.0–0.1 au; p < 0.001 for all), at POST48 in CON (1.0 ± 1.2 au; p < 0.001), POST1 in ECCWM (1.2 ± 1.7 au; p < 0.001), and POST48 in ECCWM (0.9 ± 1.3 au; p < 0.001). Conclusions: Acute maximal eccentric exercise induces greater and more prolonged decrements in muscular strength, as well as greater and more prolonged muscle soreness when compared to concentric and submaximal eccentric exercise. Practical Applications: Due to the impaired recovery of maximal strength and increased soreness, practitioners should carefully plan the implementation of maximal eccentric exercise with clients and athletes.

(12) An Examination of Squat bar Position, Body Segment Length and Squat Strength in Advanced Resistance Trained Individuals

R. Johnson,1 C. Ruot,1 L. Edwards,1 J. O'Sheilds,1 and A. Bane2

1Hardin-Simmons University; and2Abilene Christian University

The main consensus in strength training has been that high bar squats are either for quadricep hypertrophy or used as an accessory for Olympic lifting (Glassbrook, 2019). Low bar squats are for powerlifting, as it is thought to be best for maximal strength. However, there are many cases where top level powerlifters utilize high bar squats for maximal strength. This success of high bar squats in maximal strength may be due to greater lower body lean mass, or preferable limb and torso proportions for this type of squat. Purpose: The purpose of the study is two-fold: (a) to examine the difference in squat strength between high and low squat bar positions, and (b) to examine the relationship between body segment length and squat strength. Methods: The study included 14 strength trained individuals (N = 14, age: = 28.5 years ±6.87). Prior to the initial testing, subjects underwent a DEXA scan, as well as body segment length measurements. A 3 RM squat test for high bar and low bar positions at 72 hours apart was used to determine strength. A dependent t test was used to assess differences, and a Pearson correlation was used to assess relationships between variables. Significance was tested at 0.05. Results: A significant difference was found in squat strength between the high and low bar position (HB = 325.00 ± 109.30 lbs, LB = 344.64 ± 115.02lbs, t = −4.74, p < 0.05). There was no significant relationship between body segment lengths and weight lifted in the HB and LB positions. There were significant correlations between High Bar Squats and Full-Body Body Fat (r = −0.732, p = 0.003); Full Body Lean Mass (r = 0.812, p = 0.000); Full Body BMC (r = 0.761, p = 0.002); Full Body Lean Mass + BMC (r = 0.812, p = 0.000); Trunk body fat (r = −0.556, p = 0.039); Trunk Lean Mass (r = 0.767, p = 0.001); Trunk BMC (r = 0.839, p = 0.000); Trunk Lean Mass + Trunk BMC (r = 0.772, p = 0.001); Lower-Body Body Fat (r = −0.805, p = 0.001); Lower Body Lean Mass (r = 0.855, p = 0.000); Lower Body BMC (r = 0.732, p = 0.003); Lower Body Lean Mass + Lower Body BMC (r = 0.852, p = 0.000). There were significant correlations between Low Bar Squats and Full-Body Body Fat (r = −0.724, r = 0.003); Full Body Lean Mass (r = 0.819, p = 0.000); Full Body BMC (r = 0.777, p = 0.001); Full Body Lean Mass + Full Body BMC (r = 0.820, p = 0.000); Trunk body fat (r = −0.552, p = 0.041); Trunk Lean Mass (r = 0.774, p = 0.001); Trunk BMC (r = 0.851, p = 0.000); Trunk Lean Mass + Trunk BMC (r = 0.778, p = 0.001); Lower-Body Body Fat (r = −0.794, p = 0.001); Lower Body Lean Mass (r = 0.862, p = 0.000); Lower Body BMC (r = 0.746, p = 0.002); Lower Body Lean Mass + Lower Body BMC (r = 0.859, p = 0.000). Conclusions: The results indicate greater strength is exhibited in the low squat bar position. Lean mass and BMC had a significant positive relationship with squat strength in the high and low bar positions. Body fat had a significant negative relationship with squat strength in the high and low bar positions. Therefore, a lean person is able to demonstrate greater squat strength in the low bar position. Practical Applications: Based on the results of this study it appears greater lean body mass, higher BMC, lower body fat percentage, and bar position are contributing factors to squat strength. These factors being considered, the lower bar position produces the highest strength output in the squat exercise.

(13) The Effectiveness of Shorter But More Frequent Rest Periods on Mechanical and Perceptual Fatigue Management During a Weightlifting Derivative

I. Jukic1 and J. Tufano2

1Sport Performance Research Institute New Zealand (SPRINZ); and2Charles University

Research has shown that extra intra-set res periods maintain weightlifting performance, but increase total training time, which may not always be plausible. Purpose: This study investigated the effects of redistributing rest periods to be shorter but more frequent (and equal) on peak vertical barbell displacement (DISP), concentric repetition duration increment (CRDI), peak velocity decline (PVD), and perceptual exertion (RPE) over multiple repetitions, sets, and loads during a clean pull exercise. Methods: Fifteen strength-trained men performed a one repetition maximum (1RM) power clean session and 6 experimental sessions that included: 3 traditional sets of 6 clean pulls using 80% (TS80), 100% (TS100) and 120% (TS120) of power clean 1RM with 180 seconds of inter-set rest; and 3 “rest redistribution” protocols of 9 sets of 2 clean pulls using 80% (RR80), 100% (RR100), and 120% (RR120) of power clean 1RM with 45 seconds of inter-set rest. Results: When all 18 repetitions were averaged together, DISP was greater during RR100 (p = 0.008; g = 0.39) and RR120 (p < 0.001; g = 0.56) compared to TS100 and TS120, respectively. In addition, PVD was less during RR120 than TS120 (p = 0.008; g = 1.18), while CRDI was greater during TS100 (p = 0.010; g = 0.98) and TS120 (p = 0.003; g = 0.89) when compared to RR100 and RR120, respectively. The RR protocols resulted in lower RPE across the sets at all loads (p < 0.001; g = 1.11–1.24). Repetition-by-repetition analyses revealed greater maintenance of PV, PVD as well as CRD during RR compared to TS (Figure 1). Conclusions: This study is the first to show that extra intra-set rest intervals (i.e., basic cluster sets) might not always be needed to maintain performance during weightlifting movements since simply redistributing long inter-set rest intervals into shorter but more frequent inter-set rest intervals can also maintain performance through lower levels of perceptual and mechanical fatigue. Practical Applications: This study shows that, in practice, coaches should strongly consider using rest redistribution during weightlifting movements, especially at greater loads. Compared to other compound movements such as back squats and the bench press where the range of motion and technique are fairly constant regardless of the load, weightlifting movements are highly technical, and traditional sets should be avoided if maximal barbell velocity and displacement are desired. Lastly, the data in this study show that RPE mimics the changes in mechanical performance, especially with heavier loads. Therefore, RPE could be used to monitor acute fatigue during weightlifting movements. However, caution should be taken with lower (farther from failure) intensities, as RPE does not seem to be sensitive enough to detect changes in performance.

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Figure 1.:
Means and SDs for 6 collapsed repetitions (i.e., the first, seventh, and 13th repetition etc) for peak velocity decrement (panel A), peak vertical displacement (panel B), and concentric repetition duration increment (panel C) data during: rest redistribution sets (closed circles) at 80, 100 and 120% load (RR80, RR100, RR120), and traditional sets (open circles) at 80, 100 and 120% load (TS80, TS100, TS120). *Significantly less than TS (p < 0.05); **significantly less than TS (p < 0.001); †moderate effect size (g = 0.5–0.79); ††large effect size (g > 0.8).

(14) Change of Direction Deficit and Maximum Deceleration Variations Between Different Age Groups in Academy Soccer Players

L. Adams,1 K. Thomas,2 and J. Newton3

1Nuffield Health;2Northumbria University; and3Newcastle United Football Academy

Change of direction (COD) and linear sprint qualities are integral for team sport athletes, occurring during key moments within matches (i.e., scoring). One factor influencing COD ability is maturation, as the onset of adolescent awkwardness around peak height velocity might negatively affect performance of skilled, coordinative tasks; specifically, the ability to accelerate, decelerate and change direction, while effecting physical qualities such as eccentric strength. Purpose: The purpose of this study was to examine COD performance and linear acceleration and deceleration capabilities between different age groups in academy football players. Methods: Twenty-three academy soccer players (U18:n = 5,U16:n = 9 and U15:n = 9) performed 2 max effort modified 505 (M505) for both limbs, and three 40 m max sprints, with a 10 m split time (acceleration). Max deceleration performance was assessed by having the athletes stop in the shortest distance possible following the 40 m sprints. All times were recorded via electronic timing gates (Browser Timing systems, Draper) placed 2 m apart at hip height. Subjects started 1 m behind the first timing gates, with a two-point staggered stance with no countermovement. A tape measure was placed from the 40 m mark, with an athlete's distance marked for each deceleration. Three minutes of recovery was provided between each rep. A standardised warm up was performed prior to testing. Change of direction deficit (CODD) was calculated using the formula: 505 time—10 m sprint time. Mean and SD was calculated for all variables. A Shapiro Wilks test was used to assess normality. Absolute and relative reliability was measured with coefficients of variation (CV) and an interclass correlation coefficients (ICCs). A one-way-between-subject non-parametric ANOVA (Kruskal Wallace), with Bonferroni-adjusted pairwise comparisons and Hedge's g effect sizes were calculated. Results: All measures achieved acceptable reliability (CV = 0.271–1.93, ICC >0.74), except maximum deceleration stopping distance (CV = 13.5, ICC = 0.58). The U18 players were, faster than the younger age groups for all test, albeit non-significant, trivial-moderate in magnitude. However, CODD could not discriminate between age groups (p = 0.61–1.00, g = 0.11–0.61) (Figure 1). For maximal deceleration, the U15 s were significantly greater than the U18 s (p = 0.05, g = 0.79), with a non-significant trivial difference between U18 s vs. U16 s (p = 1.00, g = 0.02). The U15 s were also greater than the U16 s, albeit non-significant (p = 0.06, g = 0.81). Conclusions: The oldest age group i.e., U18's, had a greater linear speed and COD performance compared to younger athletes, but not for CODD or maximal deceleration. Practical Applications: For COD performance, both CODD and total performance time should be observed. As across age groups CODD did not change despite improvements in linear sprint qualities and M505 total performance time which would be more relevant for sports performance.

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Figure 1.:
Change of direction performance times showing the mean and individual differences between age groups. A) M505 left time, B. M505 right time, C. Change of direction deficit time left, and D. Change of direction deficit time right.

(15) Relationships Between the Jumping and Sprinting Kinetics of Elite, Collegiate Football Athletes

J. Boone,1 G. Mangine,2 T. VanDusseldorp,2 Y. Feito,2 J. McDougle,2 M. Stratton,2 and N. Velazquez2

1O2X Human Performance; and2Kennesaw State University

Speed and power are thought to be important in football athletes and these traits are indirectly assessed through a variety of field tests. Sprinting time over 10–40 yards is used as a speed metric, while standing broad jump (SBJ) distance and vertical jump (VJ) height are indicative of power. However, the resultant test scores (i.e., time, height, or distance) do not adequately describe the kinetics occurring throughout each movement, which may have greater importance to on-field success. Further, it is not clear whether kinetics during each movement are related. Strong relationships would eliminate the need to perform each assessment. Purpose: To evaluate the relationships between jumping and sprinting kinetics in elite, collegiate football athletes. Methods: Over a three-year period, 72 collegiate football athletes (22.4 ± 0.9 years, 187.0 ± 7.0 cm, 112.8 ± 23.2 kg) volunteered to complete baseline assessments of 10-yard sprinting, SBJ, and VJ, prior to initiating a preparatory training program for their respective professional football combine or pro-day. Following a standardized warm-up, each athlete completed 1–3 maximal efforts in each performance test. To measure kinetics, athletes were tethered via a waist belt to a robotic, cable-resistance device for the 10-yard sprint and SBJ, and to a linear position transducer during VJ. Peak rate of force development (RFDPeak), total work, and average force (FAVG), velocity (VAVG), and power (PAVG) were quantified during the first (STP1) and second (STP2) steps of the 10-yard sprint, while their slope was calculated across remaining steps (STPR). Peak and average values for each kinetic measure were also calculated during SBJ and VJ. To account for the influence of cord angle on resultant kinetics, partial correlations controlling for height were calculated between all sprinting and jumping variables. Results: FAVG was the only kinetic measure from STP1 related to jumping performance (SBJ RFDPeak: r = −0.24, p = 0.046). From STP2, total work was positively related to SBJ PAVG (r = 25, p = 0.039) and negatively related to average VJ force and power (r = −0.26 to −0.34, p < 0.05). Further, VJ FAVG and PAVG were negatively associated (p < 0.05) with several kinetic measures during STP2 (r = −0.25 to −0.38). Positive relationships were seen for FAVG during both STPR and VJ (r = 0.26, p = 0032), as well as between VAVG from STPR and SBJ VPeak (r = 0.39, p = 0.001), PPeak (r = 0.35, p = 0.003), and RFDPeak (r = 0.28, p = 0.018). The only negative relationship observed in relation to STPR was between its RFDPeak and SBJ PPeak (r = −0.24, p = 0.046). No other significant relationships were observed. Conclusions: The data suggests that relationships exist between standing broad jump and sprinting kinetics, but they are weak. In contrast, vertical jump kinetics only appear to be related to sprinting kinetics in a limited capacity, with higher vertical jump kinetics being associated with reduced second step sprinting kinetics. Practical Applications: Force, velocity, and power are uniquely expressed during jumping and sprinting, and enhanced performance in one movement may not translate to the other. Since short-distance sprinting, standing broad jump, and vertical jump are all thought to be important in football, athletes and coaches should continue to train for and test each of these specific movements.

(17) Influence of Rectus Femoris Cross-Sectional Area and Stiffness on Velocity, Power, and Force Production

J. Williams, L. Pacinelli, E. Serrano, and R. Thiele

Kansas State University

Muscle cross-sectional area (CSA) and mechanical muscle properties play a significant role in force production during functional movement. Previous investigations into musculotendinous stiffness have primarily utilized ultrasonography (US) imaging and dynamometry. However, few investigations have explored isolated intrinsic mechanical properties and their relationship between muscle architectural and functional performance characteristics. Purpose: Evaluate the relationship between rectus femoris CSA (CSARF), muscle stiffness (assessed via mytonometry), and peak velocity (PV), peak power (PP), and peak force (PF) production during the countermovement jump. Methods: Eleven resistance-trained males (mean ± SD; age 22 ± 3 years) volunteered to participate in this investigation. Extended-field of view US scans of the dominant limb were captured in the transverse position (Gain 50, Depth 6) and then measured via a third party image analysis software. Stiffness of the RF (RFST) was assessed using a digital mytonometry device where the average stiffness (N/m) was captured through 5 automated mechanical oscillations. All CSARF and RFST measures were assessed at 50% of the distance from the anterior superior iliac spine to superior pole of the patella with the subject leg in a relaxed position (∼0° of knee flexion). Following a 5-minute warm-up using a cycle ergometer, PV, PP, and PF were assessed with a linear positional transducer using 2 consecutive countermovement jumps (CMJ). Jumps were performed by initiating a rapid downward squat and jumping as high as possible (hands-on-hips and no knee-tuck). The mean of the 2 the CMJs were used for further analysis. Pearson product-moment correlation coefficients (r) were used to examine the relationship between CSARF and RFST as well as all CMJ characteristics with a significance level of p = ≤ 0.05. Results: Significant strong correlations were observed between CSARF and RFST (r = 0.778, p = 0.005) as well as between CSARF and all CMJ characteristics (r = 0.641–0.810, p = 0.005–0.033). Additionally, a significant strong correlation between RFST and PF (r = 0.667, p = 0.025) was observed. Interestingly, no correlations were observed between RFST and PV or PP (r = 0.406–0.519, p = 0.102–0.215). Conclusions: The results indicate that greater muscle stiffness may be associated with larger CSARF. Subsequently, functional performance, specifically peak force production measured during the CMJ, may be the result of increased muscle size and stiffness. Practical Applications: These findings suggest that larger quadriceps muscles may store more elastic energy (stiffness) potentially producing greater force during explosive movements. Programs including exercises focused on increasing muscle size and stiffness (mid-to high-repetition, eccentric-focused, resistance training), as well as rapid force production, may improve performance in explosive movements such as sprinting, jumping, and weight lifting.

(18) Short Sprints Are More Related to On-Ice Speed than Other Traditional Off-Ice Power Performance Tests

J. Hamil1, A. Triplett1, M. Vorkapich2, and J. Pivarnik1

1Michigan State University, Department of Kinesiology; and2Michigan State University, Athletic Department

Ice hockey is a high-intensity sport and players must produce substantial power and reach high skating velocities during competition. Game analyses demonstrate elite players perform 19 sprints averaging 26 m and 94 high-intensity skating bouts averaging 15–16 m during competition (Lignell et al. 2018). Consequently, power performance evaluation is critical to identify player talent for hockey professionals. Off-ice performance tests are used to evaluate ice hockey players' power, but little is known about their relationships to on-ice tests. Purpose: To compare power performance measures obtained during off- and on-ice performance tests in collegiate ice hockey players. Methods: Twenty-three male, collegiate ice hockey players (age = 18–24 years, ht = 1.82 ± 0.05 m, wt = 84.9 ± 4.74 kg) were assessed during the first transition phase of the 2019–2020 season. Off-ice performance tests included 5- and 10-yard running sprints, vertical jump (VJ), and the 30-second Wingate cycle test. The on-ice performance test was the repeat shift ability (RSA) test (Peterson et al. 2014). All tests were performed on separate days to maximize performance and rest between evaluations. Five- and 10-yard sprints were measured for time (sec) using timing gates. Sprints were performed on an indoor turf surface and players were given 2 opportunities for each distance with ∼3 minutes rest. The VJ test was used to measure jump height using a VJ tester. Players were given opportunity to retest until failure to improve on their previous jump height. The Wingate was used to assess peak power on a Monark cycle ergometer. Results were compared to the time it took to go through the first gate (G1) of the electronically timed RSA. Spearman correlations were used to assess relationships between results from each off-ice test with the on-ice test. Results: Sprint times for the 5- and 10-yard tests averaged 1.06 ± 0.06 and 1.79 ± 0.06 seconds respectively. VJ heights were 30.3 ± 2.5 in and Wingate peak power measured 997 ± 134 W. Fastest G1 skate times averaged 9.55 ± 0.43 sec. The 5- and 10-yard sprints were both significantly related to the G1 time (r = 0.416, p < 0.05; r = 0.436, p < 0.05). There were no significant relationships between VJ height (r = −0.366, ns) or Wingate peak power (r = 0.003, ns) and G1 times. Conclusions: Moderate correlations between the 5- and 10-yard sprint times and the G1 times were not surprising given both tests rely on similar energy systems and are largely influenced by players' ability to develop speed. Based on previous literature, we expect VJ and Wingate are valuable for identifying player performance potential, but these tests did not relate to the on-ice performance test. Lack of relationship between these off-ice tests and the on-ice test however should not fully discredit the use of these off-ice tests for assessing player performance as previous literature suggests off-ice tests are predictive of performance during competition. Practical Applications: When selecting an off-ice performance test to evaluate ability to develop power, on or off the ice, the 5- and 10-yard running sprints may be most applicable. Bipedal, weight bearing requirements for this test are most similar to skating locomotion compared to other tests evaluated. These tests may provide insight into players' ability to develop speed, which is necessary for achieving position or finding space during competition -elements critical to hockey strategy.

(20) Gender Differences in Peak Power During Barbell Back Squat

I. Toliver,1 R. Grow,1 E. Lindermuth,1 T. Mack,1 K. Bookamer,2 and K. Beyer1

1Bloomsburg University; and2Bloomsburg University

Purpose: The purpose of this study was to investigate the differences in absolute and relative peak power during the barbell back squat between men and women at incremental intensities. Methods: Body composition and 1-repetition maximum (1RM) of the barbell back squat were assessed in college aged men (n = 11) and women (n = 7). Fat-free mass was recorded via whole-body dual energy x-ray absorptiometry scan. Seven randomized submaximal sets of the barbell back squat ranging from 30 to 90% of 1RM were completed 48 hours after 1RM testing. For the 6 sets between 30 and 80% of 1RM, subjects completed 5 repetitions, while 3 repetitions were completed for the set at 90% of 1RM. Subjects were instructed to complete each repetition “as fast as possible,” and were provided 3–5 minutes of rest between sets. Peak power (PP) was assessed during each repetition using an accelerometer attached to the barbell. Average PP was calculated for each set and used for analysis. To ensure accuracy of loads calibrated weight plates were used during all squat testing. Furthermore, a Certified Strength and Conditioning Specialist was present for all testing to assess squat technique and maintain subject safety. Absolute PP and PP relative to FFM at all 7 loads was compared between genders using a 2 × 7 mixed factorial ANOVA with Bonferroni-adjusted post hoc tests. The alpha level was set a p ≤ 0.05, and all data are presented as mean ± SD. Results: There were no significant gender×load interactions for absolute PP (p = 0.950) or PP relative to FFM (p = 0.755). However, there were significant main effects of load for absolute (p = 0.031) and relative (p = 0.012) PP. Regardless of measure, PP at 90% was significantly lower than, or trended lower, than all other loads. Additionally, there was a significant main effect of gender when assessing absolute PP (p = 0.019), but not relative PP (p = 0.555). Regardless of load, men (1962.8 ± 542.8 W) produced significantly greater absolute PP when compared to women (1,295.3 ± 517.6 W). Conclusions: Our results suggest that men produce greater absolute PP during barbell back squat than women regardless of load. However, when comparing PP relative to body composition, men and women produce similar peak power outputs at all exercise intensities when performing the barbell back squat. Practical Applications: When assessing PP in men and women during barbell back squat, it is important to present and interpret data relative to the individual's body composition, specifically FFM. This will be especially important for any strength and conditioning coaches working with both male and female athletes and their training approach.

(21) Effects of Rotary Power & Percent Body Fat on Male Division I Tennis Athletes Serve Velocity

R. Bonnette

Texas A&M University Corpus Christi

Purpose: The purpose of this study was to investigate the effect of rotary power and percent body fat on the serve velocity of NCAA Division I male tennis athletes. Methods: Ten NCAA Division I college tennis athletes participated in this study. One month before the competitive season began subjects were tested to obtain rotary power measurements of their core (RP), percent body fat (BF) and maximum serve velocity (SV). Rotary power was assessed using the Spaniol Rotary Power test (Spaniol, 2005) and percent body fat was obtained using a Skyndex 1000B electronic skinfold caliper. Once completed, subjects were put through a brief warm-up consisting of shoulder complex exercises and practice serves. Once warm, each athlete completed 10 serves. Their maximum velocity was recorded using a Stalker Sport 2 radar gun. Results: There was a strong positive correlation between RP and SV (r = 0.775, p = 0.002). Additionally, there was a strong negative correlation between BF and serve velocity (r = −0.723, p = 0.002). Conclusions: The results of this study indicate that athletes with greater rotational power serve with superior velocity. Additionally, an inverse relationship was found between BF and serve velocity. Therefore, the athletes with more fat hit the ball with less velocity while leaner players hit it harder. These results imply that if collegiate tennis players reduce body fat, thereby increasing lean body tissue, as well as improving their rotational power, they should serve with more velocity. Practical Applications: Based on these results, collegiate strength coaches that train tennis athletes should not only include rotational power exercises in the athlete's workouts, but also address their body composition. Thus, appropriate nutritional guidelines should be shared with the athletes, as well as including aerobic training regimens to reduce body fat.

(22) Time-Motion Analysis of Division 1 Mid-Major Men's Soccer Players Relative to Quality of Competition

J. Noel, R. Lockie, J. Coburn, and S. Lynn

California State University, Fullerton

Introduction: The game of soccer requires a high level of tactical skill and fitness. Depending on the level of competition, certain players may display higher fitness capabilities than others. The quality of the opposition is thought to play a factor in determining the physiological demands of each match, which could influence movement speeds and time spent above typical high-intensity thresholds. As a result, players must be prepared for these physical demands by increasing both their aerobic and anaerobic capacities. This could be especially important for mid-major schools, whose player recruitment pools may be different from larger colleges. Purpose: To determine the difference in total distance (TD), sprint distance (SD), time spent at high-intensity thresholds, meterage, and player load performed by mid-major soccer players against higher-quality and lower-quality competition. Methods: 27 male soccer players (4 forwards, 13 midfielders, 9 defenders) from the same Division I mid-major school were assessed during the 2019 season via typical player monitoring practices. Data was collected on 20 matches. Opponents were separated into top 5 higher-quality and bottom 5 lower-quality teams based on win percentage at the end of the season, which resulted in 10 games being utilized for this study. Catapult GPS units were used for measurement, and the following metrics were analyzed: TD, SD (sprint defined as traveling above 5.5 m·s−1), time spent in high-intensity speed zones (zone 4: 5.0–7.5 m·s−1; zone 5: >7.5 m·s−1), meterage (distance covered per minute), and player load (total accelerations in 3 planes of motion/match duration; measured in arbitrary units). Averages across the 5 games for the higher- and lower-quality teams were analyzed. A 3 × 2 ANOVA (p < 0.05) and partial eta2 (small effect = 0.01; medium effect = 0.09; large effect = 0.25) calculated differences between the 3 positions and higher-quality versus lower-quality opponents. Results: A significant difference was found between opponents in TD (p = 0.015; ηp2 = 0.230) and player load (p = 0.022; ηp2 = 0.209), both of which had medium effect sizes. However, no significance differences between positions was found (p = 0.206, 0.486; ηp2 = 0.129, 0.061). No significant differences were found between opponents and position in SD (p = 0.438, 0.176; ηp2 = 0.026, 0.140), time in zone 4 (p = 0.444, 0.249; ηp2 = 0.026, 0.114), time in zone 5 (p = 0.648, 0.188; ηp2 = 0.009, 0.135), and meterage (p = 0.065, 0.192; ηp2 = 0.141, 0.134). However, each of these comparisons did have medium effect sizes. Conclusions: The quality of opponent appeared to influence the TD and player load accumulated over the course of a match, with greater values recorded against higher-quality opponents. Against better opponents, mid-major players had to cover greater running distances during the match and experiencing greater load. Although there were no significant differences in SD, time spent in zones 4 and 5, and meterage, the effect sizes may suggest some practical differences, with higher values recorded against higher-quality opponents. Practical Application: Practitioners from mid-major schools need to ensure their players have the fitness levels to tolerate the greater physiological demands (TD and player load) of the match against higher quality opposition. Ensuring players are physically prepared for the greater demands could potentially assist collegiate male soccer players through the course of the season to be more successful in match-play.

(23) The Relationship Between Softball Specific Testing and Batted-Ball Velocity in High School Softball Players

F. Spaniol

Texas A&M Univ-Corpus Christi

Purpose: To investigate the relationship between softball specific testing and batted-ball velocity in high school softball players. Methods: The subjects were 108 female athletes (age = 16.65 ± 0.89 years) who participated in summer recruiting camps sponsored by the National Fastpitch Coaches Association (NFCA). Trained test administrators used the Baseball/Softball Athletic Testing System (BATS) to collect data for height, weight, percent body fat, lean body mass, grip strength, leg power, rotary power, agility, speed, throwing velocity, and batted-ball velocity. A standard stadiometer and scale was used to measure height (65.44 ± 2.14 in) and weight (147.21 ± 22.64 lb). Biolelectrical impedance analysis was used to determine percent body fat (22.87 ± 5.66%) and lean body mass (112.54 ± 11.45 lb). A hand dynamometer was used to assess grip strength (30.59 ± 4.87 kg) while the standing long jump was used to assess leg power (69.03 ± 8.19 in). Rotational power (20.14 ± 1.96 mph) was measured with the rotary power test using a 1 kg medicine ball and radar gun. Agility (9.79 ± 0.74 seconds) was measured with the 10-yard shuttle run while running speed (3.50 ± 1.70 seconds) was determined by the 20-yard dash. Throwing velocity (52.83 ± 3.69 mph) was measured on flat ground from the traditional pitcher's stretch position, and batted-ball velocity (60.06 ± 4.08 mph) was assessed by a radar gun from 5 swings on a batting tee. Results: A correlation matrix was used to perform data analysis and correlation coefficients were calculated for all variables. Significant relationships (p < 0.05) were determined for the following: height and batted-ball velocity, r (106) = 0.31, p < 0.001; weight and batted-ball velocity, r (106) = 0.29, p < 0.002; lean body mass and batted-ball velocity, r (106) = 0.31, p < 0.001; grip strength and batted-ball velocity, r (106) = 0.39, p < 0.001; leg power and batted-ball velocity, r (106) = 0.25, p < 0.009; rotary power and batted-ball velocity, r (106) = 0.48, p < 0.001; and throwing velocity and batted-ball velocity, r (106) = 0.41, p < 0.001. Conclusions: The results of this study indicate statistically significant relationships between batted-ball velocity and height, weight, lean body mass, grip strength, leg power, rotary power, and throwing velocity. Practical Application: While it is true that correlation does not imply causation, based on the results of this study, coaches and players wishing to increase batted-ball velocity may consider strength and conditioning training to improve lean body mass, grip strength, leg power, and rotary power.

(24) Strength Predictors of Reaction Time and Movement Time During Simulated Forward Fall Arm Responses in Women Over 60

H. Legg,1 C. Arnold,2 C. Trask,2 and J. Lanovaz2

1St Mary's University, London; and2University of Saskatchewan

Purpose: Older adults may avoid serious fall-related injuries by reaching quickly with one or more hands to a sturdy surface or preparing for impact with rapid hand re-positioning to control the descent. Upper limb reaction time (RT) and movement time (MT) may be important factors contributing to this ability to avoid or mitigate a fall. Other modifiable factors such as physical function and muscle strength have also been linked to reductions in fall related injuries. The purpose of this study is to investigate the relationship of physical function, strength and falls risk to RT and MT in women over the age of 60. Methods: A convenience sample of 75 older women (72 ± 8 years, 1.6 ± 0.05 m, 72 ± 14 kg) were recruited. Arm movement was recorded using a 3D-motion capture system. From a standing position with arms by their side, subjects responded to an audible signal by reaching both arms forward to touch force plate targets positioned just below shoulder height. Three trials were conducted, with RT defined as the time from the audible sound to initiation of movement, and MT, defined as the time from initial arm movement to contact with the target. The selected physical function and strength variables were handgrip (HG), sit-to-stand (STS), timed-up and go (TUG), hand-held dynamometry (HHD) isometric shoulder flexion (SF), HHD shoulder abduction (SA), HHD elbow extension (EE), one-legged balance (OLB) and a physical activity scale for the elderly (PASE) score. Fall risk was determined by having one or more falls in the previous 12 months. Potential regression variables were first identified using correlation analyses and bivariate linear regressions. Suitable variables were utilised in separate multiple regression analyses with a step-wise backward selection method for RT and MT. Significance was set at p < 0.05 for the multiple regression analysis. Results: There were significant regression equations for both RT (F (2, 72) = 5.049, p = 0.009) and MT (F (1, 73) = 4.562, p = 0.036). Faster RT was associated with stronger HG (Beta = −0.242, p = 0.036) and a higher number of STS (Beta = −0.209, p = 0.068), accounting for 12% of the variance in RT. Additionally, women with stronger SF (Beta = −0.243, p = 0.036) had faster MT, with the model explaining 6% of the variance. Conclusions: This study provides insight into the relationship of strength and physical capabilities to RT and MT during a task simulating rapid hand and arm repositioning seen during a forward fall impact preparation. RT was related to global functional measures while MT was related to specific arm strength measures. The data suggests that a 10–20% improvement in strength and functional outcomes could reduce overall response time by up to 5% and even more for weaker individuals. This could be the difference between successful or unsuccessful arm repositioning during a forward fall. Practical Applications: An understanding of the relationship of modifiable factors to arm RT and MT provides important information for strength and conditioning practitioners working with older women, especially when designing fall injury prevention programs.

(25) A Community-Based Boxing Program Is Associated With Improved Balance in Individuals With Parkinson's Disease

A. Moore,1 E. Yee,1 B. Willis,1 E. Prost,1 A. Gray, and 2 B. Mann3

1University of Missouri;2University of Missouri-Department of Orthopaedics; and3University of Miami

Parkinson's disease (PD), a chronic and progressive neurological disorder, is estimated to impact 930,000 individuals in the United States by 2020. Impairments of PD include but are not limited to loss of balance and an increase in their fall risk by 3 times compared to age-matched clients without the disease. Community-based boxing programs are suggested to help manage the negative consequences of PD. Unfortunately, studies examining the association between participating in community-based boxing programs and disease progression in clients with PD are limited. Purpose: The purpose of this study was to examine if participation in a community-based boxing program was associated with changes in balance, as measured by the Fullerton Advanced Balance (FAB) Scale and the Timed-Up and Go (TUG) test, among clients with PD. Methods: Data was collected retrospectively from a convenience sample of individuals diagnosed with PD (n = 11 [mean age = 68 ± 4.05 years; male 73%]) participating in a Rock Steady Boxing (RSB) program. Upon being cleared by a physician to enroll, RSB classes included a 15-minute warm, 60 minutes of a high intensity boxing circuit training regimen, and a 15-minute cool down. Clients averaged 2.73 ± 1.11 visits per week over 6.73 ± 1.95 months between pre and post balance assessment completed by the same physical therapist. Balance assessment included the valid and reliable FAB Scale and the TUG. The FAB Scale includes 10 static and dynamic balance activities on a 5-point performance-based ordinal scale (0–4), with a 40/40 demonstrating the highest level of ability and a reported minimal detectable change (MDC) of 2.33. The TUG is a commonly used dynamic balance test to evaluate fall risk in older adults with a reported MDC of 3.5 seconds. Paired t-tests were used to examine differences in pre and post FAB Scale and TUG scores, with statistical significance accepted at p < 0.025 following a Bonferroni correction. Cohen's d was used to calculate effect size with ≥0.8 interpreted as large. Results: Results included a statistically significant improvement in pre and post FAB Scale scores (FAB-Pre: 32.73 ± 4.17, FAB-Post: 36.55 ± 2.84, p = 0.022), demonstrating a mean increase of 3.82 ± 1.33, above previously reported MCD, and a large effect size (d = 1.1). No statistically significant difference in the pre and post TUG scores was seen (TUG-Pre: 8.78 ± 1.77 seconds, TUG-Post: 7.36 ± 1.77 seconds, p = 0.076). Conclusions: This study found that participation in a community-based boxing program was associated with improved balance, as measured by the FAB Scale, among clients with PD. No significant differences in TUG performance was seen, underscoring the potential role of exercise specificity and balance assessment selection. Practical Application: Although the majority of PD interventions aim to slow the disease progression through maintenance of current functional abilities, this investigation found that participation in a community-based boxing program was associated with improvements in static and dynamic balance over approximately six-months. These results are encouraging with implications for clients as well as health care and fitness professionals, underscoring the value for older adults with chronic and progressive neurologic disorders to regularly participate in targeted community-based exercise programs to optimize function and reduce fall risk.

(26) Relationship Between Repeated Sprint Speed and Sprint Speed Degradation to Maximal Aerobic Capacity in Collegiate Male Soccer Players

G. Ryan, M. Eisenman, D. DeJohn, and S. Phillips

Georgia Southern University

Soccer requires significant contribution of both the aerobic and anaerobic energy systems. Coaches and technical staffs use a variety of field tests to estimate maximal aerobic capacity (V̇o2max) as well as maximum sprint speed (Smax) to determine fitness of players prior to the season. While there are benefits to field tests, such as the 12-minute Cooper Test (CT) to estimate V̇o2max, there are a number of limitations, including time and motivation, which may impact values obtained via these tests. Due to the vigorous and intermittent demands of the sport, repeated sprint performance and speed degradation (SD) may be a more sport-specific, and useful, predictor of V̇o2max in sports like soccer. Purpose: To examine the relationship between Smax and SD during 3 repeated 30 × 15 yard sprints to estimated V̇o2max in collegiate male soccer players. Methods: 17 Division I male soccer players wore a GPS bioharness and underwent the CT and 3, 30 × 15 yard repeated sprints as a team, separated by a week, as part of their conditioning program. The CT was completed using established protocol. For the 30 × 15 repeated sprints, players sprinted maximally for 30 yards, touched a line, and immediately sprinted back for 15 yards, then walked the remaining 15 yards to the initial starting point. Upon reaching the starting line, players repeated the sprint in the same manner 2 more times. Smax for each 30 (Smax30-1,2,3) and 15 yard (Smax15-1,2,3) sprint, as well as SD (difference in Smax from Smax30-1 to Smax30-3 and Smax15-1 to Smax15-3) were recorded in miles per hour from the GPS software after testing. Pearson correlations were run to evaluate the relationship between V̇o2max and all Smax and SD variables. Additionally, a forward simple linear regression was calculated to predict V̇o2max based on all variables. Significance of correlations and prediction equations was set at p ≤ 0.05. Results: A significant, moderate, positive correlation existed between V̇o2max and Smax30-2 (r (17) = 0.49, p = 0.05) and a significant, moderate, negative correlation existed between V̇o2max and S30D (r (17) = −0.50, p = 0.04). A significant regression equation was found (F (1,16) = 4.95, p = 0.04; R2 = 0.25). S30D was the only significant predictor of V̇o2max (V̇o2max = 65.197–4.260(S30D)). 95% CIs were (57.266–73.129) and (−8.343 to −0.178) respectively. Neither S15D nor any Smax values were significant contributors (p > 0.05). Conclusions: Players who maintained Smax (smaller SD) across sprints had higher V̇o2max compared to those with higher SD during the test. Only a modest relationship existed between Smax during any sprint (Smax30-2) and V̇o2max, indicating that the ability to maintain speed during 30 yard repeated sprints is a better predictor of aerobic performance than Smax. S30D shows promise as an estimator of V̇o2max in collegiate male soccer players. Practical Applications: The ability to maintain Smax is a major determining factor to increased aerobic capacity among soccer players. Strength and conditioning staffs may want to focus on repeated sprint performance in training to help match both aerobic and anaerobic demands of the sport. Lastly, due to the smaller time commitment of the 30 × 15 repeated sprints (∼3 minutes) and increased specificity, coaches and technical staffs may want to consider S30D as a value for estimating V̇o2max in collegiate soccer players. However, more testing is needed before relying solely on this method for determining V̇o2max.

(27) Effect of Maturity Status on Drop Jump Performance in Elite Male Youth Soccer Players

J. Pedley,1 R. Lloyd,1 P. Read,2 Z. Gould,1 and J. Oliver1

1Cardiff Metropolitan University; and2Aspetar Sports Medicine Hospital

Introduction: Good drop jump performance is characterised by spring-mass like behaviour underpinned by effective use of the stretch-shortening cycle (SSC) to store kinetic energy in the elastic components of the muscle-tendon unit [1–3]. Drop jump ground reaction forces have been shown to be sensitive to the physiological changes that occur as a result of maturation [4] though little is currently known about the effect of maturity status on these variables. Purpose: To assess the effects of maturity status on a range of novel and traditional drop jump ground reaction force variables in elite male youth soccer players. Methods: 264 subjects (age: 13.95 ± 1.99 years; height; 162.3 ± 15.2 cm; body mass; 52.27 ± 13.99 kg; maturity offset: −0.19 ± 1.85 years) from the academies of 6 elite English soccer clubs agreed to take part in the study. Maturity offset was calculated using the equation of Mirwald et al. [7]; subjects were then determined to be either pre-PHV (maturity offset < −1.0), circa-PHV (−0.5 < maturity offset < +0.5) or post-PHV (maturity offset > +1.0). Following familiarization, subjects performed the testing session which required 3 trials of a 30 cm drop jump onto a force plate (Pasco, USA) sampling at 1,000 Hz. Ground reaction force data was processed to calculate a variety of variables; jump height (JH), ground contact time (GCT), reactive strength index (RSI), center of mass displacement (CoM), vertical stiffness, peak force (PF), peak braking force (PBF), peak propulsive force (PPF), timing of PBF and PPF and spring-like behaviour correlation (SLC). Results: There were no significant differences between any of the groups for GCT (p < 0.05). Significant increases in JH (pre-PHV: 23.74 ± 4.53 cm; circa-PHV: 28.36 ± 6.61 cm; 32.10 ± 4.78 cm) and RSI (pre-PHV: 0.79 ± 0.22; circa-PHV: 0.91 ± 0.24; post-PHV: 1.09 ± 0.31) were observed between consecutive maturity groups (p < 0.05). PBF was significantly greater in pre-PHV (4.17 ± 1.03 BW) than both circa- (3.66 ± 0.75 BW) and post-PHV (3.63 ± 0.80 BW) (p < 0.05). There were no significant differences between maturity groups for PPF (p < 0.05). PBF occurred significantly earlier in pre-PHV (57 ± 14 ms) than circa-PHV (68 ± 20 ms) and post-PHV (74 ± 18 ms) (p < 0.05). There were no differences between any maturity groups for the timing of peak propulsive force (p < 0.05). SLC increased significantly between each maturity group (pre-PHV: 0.82 ± 0.16; circa-PHV: 0.89 ± 0.09; post-PHV: 0.91 ± 0.09) (p < 0.05). Conclusions: Pre-PHV elite male soccer players tend to display poor spring-like behaviour which is characterised by greater ground reaction force in the early period of GCT; this is typically considerably larger than the PPF. Improved SSC function would facilitate improved reutilisation of elastic energy which appears to manifest as greater jump height rather than shorter ground contact times as young athletes mature. Practical Application: RSI is traditionally used to determine drop jump performance but the underlying kinetic variables that drive SSC function might offer greater insight into suitable coaching and training interventions in order to direct athletes towards a more spring-like profile. Research addressing the effect of cueing styles on drop jump performance demonstrates that directing an athlete's attention towards minimising ground contact time results in a larger peak landing force that occurs earlier during ground contact [8, 9].

(28) The Association Between Body Composition and Performance Assessments With External Workload Metrics in Division II Collegiate Women's Soccer

S. Wroblewski, T. Morrison, K. Anderson, A. Murphy, A. Bedsole, J. Sullivan, E. Souza, and J. Andersen

University of Tampa

Introduction: Aerobic fitness is known to be critical for performance in intermittent sports such as soccer. The Yo-Yo intermittent test is a soccer-specific assessment that measures an athlete's capacity to continually perform interval running and is reflective of aerobic fitness. There are many factors, including body composition that are thought to play a role in an athletes' aerobic capacity and performance. For instance, a higher percentage of body fat has been associated with a decrease in athletic performance, particularly in sports where body mass is transferred horizontally and/or vertically. Global Positioning System (GPS) and Inertial Movement Units (IMU) allow for field performance, specifically external workloads such as volume (Total Distance-TD), intensity (Meters Per Minute-M·Min−1), and explosiveness (Total Acceleration Load-TAL) to be measured during practices and matches. Unfortunately, such technology is not available to most coaches in collegiate Division II women's soccer (D2S). Therefore, the association between body composition and on-field assessments with GPS metrics related to field performance is still unknown within D2S. Purpose: The purpose of this investigation was to determine the relationship between body composition and the Yo-Yo intermittent test with GPS field metrics. Methods: Sixteen female soccer athletes (19.6 ± 0.86 year old; 62.0 ± 9.6 kg) were monitored during the Yo-Yo endurance assessment (20-meter shuttle run with 10-second recovery) during off-season practice in Spring 2020 using GPS and IMUs (Catapult Sports Innovations). The final level completed prior to failure for each athlete was recorded and data was collected for TD, M·min−1, and TAL. Dual energy X-ray absorptiometry (DEXA) was used to measure whole and regional body composition. Additionally, a region of interest marked from the iliac crest to lateral condyle (ROI-FFM) was assessed in the lower extremities. GraphPad Prism 8.1 was used to examine the correlation between Yo-Yo level, FFM, FM, ∑ROI-FFM, ∑ROI-FM, and BF% with TD, M·min−1, and TAL utilizing a multiple variable analysis, with p < 0.05 considered statistically significant. Results: The results of the correlation analyses and their respective 95%-confidence intervals are presented in Table 1. Conclusions: Moderate negative relationships were found for FFM, FM, ∑ROI-FFM and ∑ROI-FM with M·MIN−1, TD, and TAL. Interestingly, we observed moderate negative relationships between FFM and ∑ROI-FFM with M·MIN−1, plausibly due to an increase in the individual's total mass. A strong positive relationship between Yo-Yo level completed and each field metric was observed, particularly with the explosiveness measure (TAL). Practical Application: Coaches who do not have access to GPS technology may consider the correlation between the Yo-Yo intermittent test and GPS field metrics, suggesting the higher the completed level, the more intense and explosive the athlete's session.

Table 1 - Correlation and 95%-confidence intervals summary.
M·min- meters per minute; TD- total distance; TAL- total acceleration load; FFM- fat-free mass, FM- fat mass; BF%- body fat percentage; FFMI- fat-free mass index; ∑ROI-FFM-sum of regional fat free mass in both legs; ∑ ROI-FM- sum of regional fat mass in both legs * = Indicates significant correlation between variables (p < 0.05).

(29) A 10-Week Sit and Resistance Training Intervention Evaluating Body Composition, Aerobic Fitness, and Muscular Strength Changes in Sedentary Women

A. Peart, K. Suire, M. Merritt, J. McDonald, and D. Wadsworth

Auburn University

Current literature indicates that combined aerobic and resistance training (RT) is an effective modality to elicit physiological benefits to increase human performance (Banitalebi et al., 2019 Maiorana et al., 2000). However, there is limited research on the effects of combined exercise interventions on sedentary women that include sprint interval training (SIT) as the aerobic component. Purpose: The purpose of this study was to examine how the application of a 10-week combined SIT and RT intervention would affect body composition, aerobic fitness, and muscular strength in sedentary women. Methods: This intervention consisted of one experimental group, a SIT and RT combined group attending 10 weeks of exercise training (3×·wk−1; total of 30 sessions). Paired samples t-tests compared pre and post body composition, and V̇o2max. A repeated-measures ANOVA examined differences in the pre, mid (week 5), and post estimated one repetition maximum (1-RM) for the squat and bench press measures. Only individuals that completed all measurements for that specific variable were included in analysis. Results: Fat mass decreased significantly (p = 0.004; pre 41.57 ± 14.65 kg; post 40.67 ± 15.09 kg), and lean body mass increased significantly (p < 0.001; pre 46.36 ± 14.91; post 47.55 ± 7.13 kg). V̇o2max significantly increased (p < 0.001; pre 23.65 ± 4.96 ml·kg−1·min−1; post 28.11 ± 6.46 ml·kg−1·min−1). Back squat significantly increased (p < 0.001) from pre (27.73 ± 9.83 kg) to mid (46.92 ± 11.67 kg), pre to post (60.32 ± 13.49 kg), and mid to post training. Bench press significantly increased (p < 0.001) from pre (22.32 ± 7.64 kg) to mid (36.36 ± 7.58 kg), pre to post (41.53 ± 8.24 kg), and mid to post-training. Conclusions: This study revealed that a combined 10-week SIT and RT intervention can significantly decrease fat mass while also increasing lean body mass, V̇o2max, and muscular strength in sedentary women. In addition, there are limited combined (SIT + RT) exercise interventions to compare data for this population which makes this study novel. Practical Application: Physicians, coaches,and personal trainers can utilize this exercise intervention to improve the health and human performance of sedentary women in their care.

Table 1 - Physiological changes in body composition, aerobic fitness, and muscular Strength, Mean ± SD.

(30) The Effect of a 12-Week Resistance Training Program on Anaerobic Performance in First-Year Collegiate Dancers

B. Parker,1 J. Sudock,1 R. Amylon,2 C. Schall,1 and M. Mays1

1Shenandoah University; and2Boston University

Purpose: The purpose of the present study was to assess anaerobic performance in first-year collegiate dancers following a 12-week resistance training program. Methods: Five first-year female dance students (N = 5; age: 18 ± 0 years) from the same institution volunteered to participate in this study, which was conducted during the first semester of the dance program. Prior to a twice-weekly, 12-week resistance training (RT) program, subjects completed the Wingate Anaerobic Test (WAnT), a 30-second all out cycling test. The WAnT resistance was set at 0.075 kp·kg−1 body mass (BM). The mean absolute peak power (PP), relative PP normalized to the BM, and the fatigue index were calculated. Following the RT program, subjects were tested again utilizing the same parameters and calculations. Results: No significant differences were found from baseline (7.58 ± 1.92 W·kg−1) to post-testing (8.82 ± 1.39 W·kg−1) for peak relative power (p = 0.052). No significant differences were found from baseline (41.53 ± 9.33%) to post-testing (33.27 ± 6.31%) for fatigue index (p = 0.143). A significant difference was found from baseline (377.98 ± 83.59 W) to post-testing (486.32 ± 53.98 W) for mean absolute power (p = 0.012). A significant difference was found from baseline (5.73 ± 1.49 W·kg−1) to post-testing (7.14 ± 0.67 W·kg−1) for mean relative power (p = 0.028). Conclusions: An improvement was seen in terms of the dancers' anaerobic capacity after completing the 12-week resistance training program, indicating the dancers were able to produce a higher amount of muscular power. While not significant, the trend in relative peak power indicates an overall improvement. Improvements in peak power enable dancers to produce a greater amount of force in a 5-second time frame. Decreasing fatigue index represents the ability to maintain power output for a longer duration of exercise. Improvements in mean power indicated that the dancers were able to produce a greater amount of force for the entire duration of the WAnT. Practical Application: The implementation of a formalized RT program is vital to the improvement of power in dancers. Previously, the anaerobic contribution to a dance performance has been analyzed and indicated that dancers have multiple high intensity powerful bouts during a dance performance (Koutedakis & Jamurtas, 2004). Through periodized resistance training programs, dancers can improve their anaerobic power and decrease the rate at which they are fatiguing the anaerobic energy systems. Decreasing the rate of fatigue (fatigue index) will improve dancers' longevity in performance. Improvements in power output will translate to improved performance of dance specific movements requiring large surges in power, such as grand allées and series of adagios (Koutedakis & Jamurtas, 2004). Dancers are performing athletes whose training often overlooks strength and power in favor of technique and artistry; leading to the inability to generate sufficient power to sustain multiple performances containing high intensity movements and increased risk of injury (Koutedakis & Jamurtas, 2004). As demonstrated within this study, the implementation of a periodized strength and conditioning program can benefit collegiate dancers anaerobic performance.

(31) Effect of Moderate vs. High-Intensity Resistance Training on Oxidative Stress Markers and Antioxidant Capacity in Older Women

F. Martin,1 P. Gargallo,2 G. Saez,2 C. Bañuls,2 J. Flandez,3 A. Juesas,2 and J. Colado2

1University of Valencia-Spain;2University of Valencia; and3University of Valdivia

Aging is associated with an imbalance between the reactive oxygen species (ROS) and the antioxidant defense system, in favor of the first one. It is well known that ROS could react with several different organic structures, such as lipids and proteins, causing cell dysfunctions in the elderly. Oxidative stress (OS) and antioxidant response induced by physical exercise may vary with the characteristics of the exercise, such as intensity or modality. Little is known about the effects of the resistance training on the OS and the antioxidant capacity in older women. PURPOSE: to investigate the effects of 16-week progressive resistance training (PRT) with elastic bands (EB) at 2 different intensities on OS makers and the antioxidant capacity in older women. Methods: 70 sedentary older women (70 ± 6.26 years) were randomized into moderate intensity group (MOD) (n = 23), high intensity group (HIGH) (n = 28) and control group (CG) (n = 19). The exercise groups performed a PRT program twice a week for 16 weeks. Both training groups performed 3–4 sets of 6 (HIGH) or 15 (MOD) repetitions of 6 overall body exercises (3 for upper and 3 for lower extremities) with a speech of execution of 2 seconds for each phase, and a rate of perceived exertion (OMNI-RES EB scale) of 6–7 during the first 4 weeks and 8–9 for the rest of the training period. All training groups used EB. Lipid peroxidation markers (malondialdehyde [MDA], F2-isoprostane [F2-iso]) along with makers of protein oxidative damage (protein carbonyls [PCO]) were assayed in blood mononuclear cells and urine. The antioxidant capacity was determined by evaluation of the enzymatic activity of catalase (CAT), glutathione peroxidase (GPX) and superoxide dismutase (SOD). Intention-to-treat analysis with repeated measures ANCOVA (3 group × 2 time) adjusting for age and baseline values was performed. Results: MOD showed a significant (p < 0.05) reduction in lipid peroxidation (MDA: −16.8%) and a significant increase in the CAT activity (+4.7%). In addition, MOD also found improvements in F2-iso (−8.3%) and SOD activity (+2.1%) without statistical significance as also happened in PCO (+2.1) and GPX (−3.7). HIGH increased significantly the lipid peroxidation (F2-iso: +14.6%) and the antioxidant capacity thought the decrease of the GPX activity (−8.9%). No significant changes were found in the rest of the parameters (MDA: −5.9%; CAT: +1.7%; SOD: +0.4%; PCO: +1.7%). There were significant differences between MOD and CG in MDA and between HIGH and CG in GPX. Conclusions: 16-week PRT program with EB at a moderate intensity can improve OS by decreasing the lipid damage and increasing the antioxidant capacity in older women while a similar high-intensity training protocol produces the opposite effect. These findings reveal a possible dose–response relationship. Practical Application: Due to the chronic OS state has been associated with important diseases, disability and death in the elderly, trainers and clinician have to know that implementing a resistance training program at moderate intensity may be better strategy for reducing OS and improving antioxidant capacity than high intensity in older women.

(32) Perceived Exertion and Recovery Status Scores Comparisons in Professional Male Soccer Players and Coaches

S. Rossi, M. Eisenman, D. DeJohn, S. Phillips, and G. Ryan

Georgia Southern University

Perceived Recovery Status (PRS) and Rating of Perceived Exertion (RPE) are 2 subjective methods coaches, athletes, and sport scientists have used to quantify training load (TL) and recovery to improve athletic performance. While these values are important to monitor, these tools are more useful if there is an agreement between coaches and players. It is important the prescribed TL matches what the athlete is experiencing during training. Purpose: The intent of this study was to assess subjective measures (PRS and RPE scores) received from athletes and coaches during the course of a 36 weeks competitive season. Methods: PRS scores prior to, and RPE scores after, each practice were collected on 24 professional male soccer players (P) and 2 coaches (C). Athletes were provided a visual of the scale prior to answering each day and each athlete reported their scores away from other athletes and coaches. Coaches were instructed to provide answers to PRS and RPE as to how the players on the team felt. The average of RPE and PRS values from each week (Wk) for both P and C was used for all analyses. Due to the categorical nature of the data, nonparametric Mann-Whitney U Tests were run comparing P to C data for each Wk. Significance was set at p ≤ 0.05. Results: P and C PRS comparisons were significantly different for half of the Wks during the season: Wk9 (median P: 7.0, C: 6.0; p = 0.01), Wk16 (P: 7.0, C: 6.0; p = 0.02); Wk17 (P: 7.0, C: 6.0; p = 0.01); Wk19 (P: 7.0, C: 6.0; p = 0.01); Wk21 (P: 7.0, C: 6.0; p = 0.01); Wk24 (P: 7.0, C: 6.0; p = 0.03); Wk25 (P: 8.0, C: 6.0; p < 0.01); Wk26 (P: 7.0, C: 4.0; p < 0.01); Wk27 (P: 7.0, C: 6.0; p = 0.01); Wk28 (P: 7.0, C: 6.0; p < 0.01); Wk29 (P: 7.0, C: 6.0; p < 0.01); Wk30 (P: 7.0, C: 4.5; p = 0.01); Wk31 (P: 7.0, C: 5.5; p = 0.01); Wk32 (P: 7.0, C: 4.5; p = 0.01); Wk33 (P: 7.0, C: 5.5; p < 0.01); Wk34 (P: 7.0, C: 5.5; p = 0.02); Wk35 (P: 7.0, C: 6.0; p = 0.01) and Wk36 (P: 7.0, C: 6.0; p < 0.01). Average P and C RPE were not significantly different (p > 0.05) for any of the 36 weeks. Conclusions: Results indicate that RPE of practice were similar between P and C throughout the season. C tended to underestimate P self-reported recovery, especially as the season progressed into the latter third of the season. P PRS scores were more consistent throughout the season compared to C. Practical Applications: This is an important consideration for coaching and training staffs when managing athlete TL and recovery. While team averages of PRS and RPE are important, individual P data is also important to track due to individual differences in response to TL. Individual athlete data allows the coaching staff to make specific changes to a specific athlete's recovery plan and future TL.

(33) Game Demands in Male Elite U20 Basketball

T. McGann,1 S. Snodgrass,2 A. Schultz,1 M. Drew,3 K. Dooley,2 L. Donnan,4 T. Pizzari,5 E. Rio,5 and S. Edwards2

1The University of Newcastle;2The university of Newcastle;3The Australian Institute of Sport;4Charles Sturt University; and5La Trobe Sport and Exercise Medicine Research Center, (ACRISP one of the IOC Centers), La Trobe University

Physical game demand data and indices of player participation load in indoor sports like basketball are used by coaches and training support staff to monitor athlete wellbeing and prescribe appropriate individualised training. Measuring game demands indoors have previously been limited to 2-dimensional video monitoring technologies that inherently provide limited measurement accuracy, as opposed to newer and highly accurate local positioning system (LPS) technology. Purpose: This study aimed to quantify physical game demands in elite-level U20 basketball using LPS technology. Methods: Thirty-five elite male U20 basketball athletes (age 16.8 ± 1.1 years) were recruited to participate in a five-day scouting camp held at the Australian Institute of Sport. Subjects were selected into one of 4 teams, and competed in 2 four-quarter basketball games, played within a 48-hour period. Players were tracked in-game via LPS (Catapult Clearsky T6) with data analysed post-game using 6 previously established speed bands to categorise individual total distance travelled within each band. Repeated measures analysis of variance was performed to assess the interactions between Game, Quarter and Band. Results: On average, athletes covered 3,285 ± 881 m per player per game. Players covered a greater distance in Band 2 (1,708 ± 91 m; moderate-to-high speed running; 1.67–4.17 m·s−1) compared to Band 1 (1,170 ± 62 m; standing/slow walking; 0–1.67 m·s−1; p = ≤0.05), with both bands together equating to 85% of the total distance covered by a player within a game. Only 3 players (8%) reached sprint speeds greater than 6.7 m·s−1 (Band 6). After half-time (Quarter 3), players covered a significantly greater distance in Bands 1 (313 ± 15 m; p ≤ 0.05) and 2 (466 ± 28 m; p ≤ 0.05) than in any other Quarter. Conclusions: In the present study players covered the greatest in-game distance at low movement speeds with only limited high intensity efforts. Revised basketball-specific speed bands are proposed to more accurately characterise the movement speeds observed when jogging, walking and running during basketball game play. Practical Application: Revised speed bands will better characterise lower-speed game demands in basketball, and will thereby enable coaching staff to more accurately monitor player game load. Higher total distance covered in-game during Quarter 3 has implications for half-time recovery practices and coach tactical decision making.

(34) Documenting Cardiac Autonomic Function in Female Collegiate Volleyball Players: a Freshman and Senior Comparison

R. Edmonds, J. Matthies, S. Bankers, and B. Schmidt

Creighton University

Heart rate (HR) variability (HRV) is a well-known tool used to asses cardiac autonomic function across a multitude of populations. Specifically, its use to identify potential training maladaptation and readiness to compete has garnered significant attention with coaches and sport scientists across a broad range of sports. Purpose: To examine the relationship between HR, HRV and athlete self-reported measures of sleep, fatigue, muscle soreness, stress, mood, and diet in 2 collegiate volleyball players, one in their senior year and another in their freshman year. Methods: Each morning upon awakening, a 55-second HRV measurements were taken using a smartphone application and pulse-wave finger sensor. Athletes self-reported measures were also recorded daily after completing the HR recording. Subjective measures of sleep, fatigue, muscle soreness, stress, mood, and diet were recorded on a 1–10 scale. Spearman's rank-order correlations were used to assess relationships between HRV and the athlete self-reported measures. Results: The average daily HRV score for the senior athlete was 90 ± 6.9 ms, while the average daily HRV score for the freshman athlete was 83 ± 7.9 ms. No significant relationships were reported between HRV and sleep (r = −0.042), fatigue (r = −0.079), muscle soreness (r = 0.021), stress (r = −0.202), mood (r = −0.181), and diet (r = 0.049) for the senior athlete. A significant negative correlation was observed between HRV and stress (r = −0.254; p = 0.045) for the freshman athlete, with no other significant relationships identified between HRV and sleep (r =0.052), fatigue (r = −0.122), muscle soreness (r = −0.071), mood (r = 0.017), or diet (r = −0.160). Conclusions: These results suggest that as HRV decreases, self-reported levels of stress increase for the freshman athlete, while the senior athlete shows no such relationship. Practical Application: The results of this investigation may indicate that freshman athletes are potentially be more susceptible to the increased stress associated with both academic and athletic workload. Careful attention as to a collegiate athlete's overall health and wellbeing should be considered, especially those in their freshman year.

(35) Muscular Strength and V̇o2 are Associated With C-Reactive Protein Expression in Normal Healthy Adults

J. Winchester,1 A. Scott,2 C. Scott,3 and F. Wyatt4

1University of the Incarnate Word;2Women's Health Physical Therapy/Men's Pelvic Health;3Virginia Commonwealth University; and4Midwestern State University

Recent studies show that exercise has the ability to reduce C-reactive Protein (CRP), potentially reducing acute phase proteins which can signal cardiovascular distress. Determining the physiological adaptations to physical training which most closely corresponds to a reduction in CRP levels may serve to shed light on the most appropriate training methods for the decreased of risk in obtaining cardiovascular disease. Purpose: To evaluate physical attributes, which accompany specific modes of exercise having the potential to influence serum levels of CRP. Methods: Twenty-nine (n = 29) subjects (age: 24.9 ± 6.6 years, height: 169.3 ± 8 cm, mass: 72.9 ± 14.9 kg) participated in the investigation. Body composition, body mass index (BMI), waist-to-hip ratio (WHR), serum CRP levels, resting heart rate and blood pressure, oxygen consumption (V̇o2max) estimation based on a V̇o2 estimate test, along with a dynamic strength test for upper and lower body were assessed. Association and prediction between attribute variables and CRP was determined for the entire data set and also in a stratified manner by separating subjects into the bottom and top 50% for individual attribute variables via a Pearson Product Moment Correlation and a stepwise regression analysis. Post-hoc analysis included a dependent samples t-test to compare variables between groups showing statistical significance (p < 0.05). Results: Negative correlations were observed between CRP and V̇o2max, along with CRP and fat free mass (FFM) (r = −0.67 and r = −0.87, respectively). Positive correlation is shown between CRP and body fat (BF), along with CRP and BMI (r = 0.87 and r = 0.78, respectively). Variables significantly contributing to strengthening the regression equation for CRP were body fat (BF), body mass index (BMI), waist to hip ratio (WHR), leg press (LP), bench press (BP), and resting diastolic blood pressure (RDBP). The equation resulted in an r = 0.99, with p < 0.002. A second regression analysis showed both V̇o2max and LP as a significant predictor of CRP (r = 0.73, p < 0.046). BF showed significance as a predictor for CRP (r = 0.87, p < 0.0006). Conclusions: The association with CRP and body composition variables are well established. However, components of physical fitness, in particular muscular strength, are not noted prominently as being important components to manipulating CRP. The results of our study suggest that, beyond considerations of body composition, focus on attributes of physical fitness such as aerobic capacity and muscular strength, may have the potential to reduce levels of CRP. Practical Application: This information can potentially be used to prioritize training goals for persons who are seeking to reduce their risk of cardiovascular disease, or by medical or fitness professionals who desire to provide evidence-based recommendations to at-risk clients.

(36) Quantifying the Environmental Thermal Conditions That Existed During the 2019 NCAA Outdoor Track & Field Championships in Austin, Texas

J. Gonzalez,1 K. De Los Santos,2 A. Becerra,1 and S. Santana1

1The University of Texas Rio Grande Valley; and2Schreiner University

The 2019 NCAA Outdoor Track & Field Championships were held at Mike A. Myers Stadium in Austin, Texas June 5 to June 8, 2019. The thermal and environmental conditions on those 4 days of competition were held in typical Texas summer hot and humid weather. Purpose: To quantify via the Weather Channel the environmental thermal conditions that track & field officials, volunteers and track & field athletes are exposed during the 4 days of NCAA Outdoor Track & Field Championship. Methods: Air temperature (F), feels like (F), wind speed (mph), dew point, humidity (%), pressure (in), and ultraviolet index (UVI) were documented from the Weather Channel App at 8:00 am 10:00 am, 12:00 pm, 2:00 pm, 4:00 pm, 6:00 pm, 8:00 pm and 10:00 pm throughout the 3 days of the competition. Results: The mean air temperature reading, SD, for the 2019 NCAA Outdoor Track & Field Championships were 8 am 74.67ºF ± 0.57; 10 am 83.0 ºF ± 2.51; Noon: 87.33 ºF ± 3.05; 2 pm 94.00 ºF ± 1.52; 4 pm 83.67 ºF ± 10.78; 6:00 pm 87.00 ºF ± 8.71; 8:00 pm 86.67 ºF ± 5.29; 10:00 pm 80.67 ºF ± 4.04. The mean temperature feels like were 8 am 74.67 ºF ± 0.57; 10 am 86.67 ºF ± 2.51; Noon: 91.67 ºF ± 3.21; 2 pm 97.00 ºF ± 1.0; 4 pm 92.33 ºF ± 13.31; 6 pm 94.67 ºF ± 8.73; 8 pm 92.67 ºF ± 6.50; 10 pm 85.67 ºF ± 7.50. The mean windspeed readings were 8 am 2.33 ± 0.57; 10 am 2.67 ± 2.081; Noon: 3.3 ± 0.57; 2 pm 3.67 ± 2.08; 4 pm 5.33 ± 3.78; 6 pm 5.33 ± 3.21; 8 pm 5.33 ± 2.51; 10 pm 2.67 ± 1.52. The mean due point readings were 8 am 67.33 ± 0.57; 10 am 67.00 ± 1.0; Noon: 66.67 ± 1.15; 2 pm 66.00 ± 2.64; 4 pm 65.33 ± 1.52; 6 pm 66.67 ± 3.05; 8 pm 67.33 ± 2.08; 10 pm 69.00 ± 2.64. The mean pressure in inches readings were 8 am 29.45 ± 0.60; 10 am 29.80 ± 0.03; Noon: 29.80 ± 0.03; 2 pm 29.77 ± 0.033; 4 pm 29.74 ± 0.03; 6 pm 29.72 ± 0.02; 8 pm 29.73 ± 0.02; 10 pm 29.76 ± 0.02. The mean UVA index readings were 8 am 0.00 ± 0; 10:00 am 4.67 ± 1.15; Noon: 9.33 ± 0.57; 2 pm 11.00 ± 0.0; 4 pm 5.67 ± 2.30; 6 pm 2.00 ± 0.0; 8 pm 0.00 ± 0.0; 10 pm 0.00 ± 0.0. Conclusion: Data from the Weather Channel App suggests that the critical times heat times during the 2019 NCAA Outdoor Track & Field Championships was between 2 pm and 6 pm Extra care must be taken with the UVI readings peaking at 2 pm Although for running events low wind speeds are considered optimal, this does not allow for good convection in cooling off the body during these high temperatures. Practical Application: Although the Outdoor Track & Field Championships are only being held in Texas during the 2019 and 2020 years, good care must be taken to address the peak heat and UVI readings during the middle part of the day. Pro-active care must be taken to address pre-competition and post-competition cooling off the core effectively and efficiently. It is recommended that Wetbulb Globe Temperature readings be taken during this type of outdoor competition to ensure more effective monitoring of heat and humidity.

(37) Physiological Characteristics of Male U.S. Soccer Development Academy Players: Differences Between Age Groups and Player Positions

A. Chandler,1 H. Cintineo,1 M. Arent,1 B. McFadden,1 B. Bozzini,2 A. Walker,3 A. Poyssick,4 N. Mackowski,5 W. Maldonado,4 and S. Arent1

1University of South Carolina;2University of South Carolina Sport Science Lab; Rutgers, The State University of New Jersey;3Lebanon Valley College;4Rutgers University; and5Air Force Research Laboratory

Elite youth soccer players differ both physically and physiologically from their non-elite counterparts, but data in elite youth athletes are limited. Assessing characteristics by both chronological age and by player position may provide information regarding normative athlete characteristics that relate to sport performance. Purpose: To assess physiological characteristics of elite youth male soccer players and evaluate differences between age groups and on-field player positions. Methods: Elite youth male soccer players (N = 86) completed a single testing session to assess physiological characteristics. Percent body fat (BF) and fat-free mass (FFM) were determined using air-displacement plethysmography and athlete-specific density equations. Countermovement jump (CMJ) height was measured and used to calculate absolute (W) and relative (W·kg−1) anaerobic power. Aerobic capacity (V̇o2max) was determined by indirect calorimetry during a maximal graded exercise test. Differences between age groups (U15: n = 39 Mage = 14.3 ± 1.0 years; U18: n = 47; Mage = 16.8 ± 0.8 years) were assessed using independent t-tests and differences by on-field positions (forward [FW], defender [DF], midfielder [MD], goalkeeper [GK]) were analyzed using one-way ANOVA with Tukey HSD pairwise comparisons (α = 0.05). Results: U18 were taller (+7.2 cm), heavier (+13.0 kg), and had more FFM (+12.6 kg), yet lower V̇o2max (−2.8 ml·kg−1·min−1) than U15 (p < 0.01). CMJ was higher in U18 (+4.2 cm; p = 0.02) and relative power was greater in U15 (+8.3 W; p = 0.03), but there were no differences in absolute power output. Player characteristics (mean ± SD) by position are displayed in Table 1. GK were taller than MD (p = 0.002), heavier than MD (p < 0.001) and DF (p = 0.03), and had higher BF than FW (p = 0.01). MD were shorter than FW (p = 0.02) and DF (p = 0.04), weighed less than FW (p = 0.01), and had lower FFM compared to both FW (p = 0.003) and GK (p = 0.004). While V̇o2max did not differ by position, CMJ was higher in FW compared to MD (p = 0.04). Both GK and FW produced more absolute power than DF and MD (p < 0.05), but there were no differences in relative power by position. Conclusions: Anthropometrics and CMJ varied by both age and position, but V̇o2max only differed by age. The higher FFM and total bodyweight in the older athletes may contribute to their higher CMJ yet lower relative power and V̇o2max. Higher absolute power production among GK and FW, along with the physical differences between positions, is likely reflective of varying positional demands. Practical Application: Anthropometric characteristics may be determinants of on-field success among elite male youth soccer athletes. The impacts of age, physical maturation, and development on performance suggest it is beneficial for athletes to compete within their age cohort rather than advance prematurely, as a smaller body size may place younger athletes at a disadvantage.

Table 1 - Player characteristics.
Characteristics (mean ± SD) by player position.

(38) Isokinetic Shoulder Strength Profile of Collegiate Baseball Pitchers

D. Szymanski, M. Qiao, V. Singh, and D. Cloud

Louisiana Tech University

Purpose: To evaluate the isokinetic shoulder strength and add to the normative data profile information of collegiate baseball pitchers. Methods: Nineteen Division I baseball pitchers (age = 19.9 ± 1.5 years, height = 186.5 ± 5.9 cm, body mass = 90.7 ± 13.8 kg, % body fat = 14.6 ± 5.2%) volunteered for isokinetic strength testing of external rotation (ER) and internal rotation (IR) of the shoulder. Testing was performed with each pitcher's arm abducted 90° and the elbow flexed 90° while seated in an isokinetic dynamometer set at 180, 300, and 450°·s−1. Before testing, all pitchers completed a warm-up (WU), which consisted of 6 standing upper body dynamic arm swing movements followed by a 5-minute seated upper body ergometer WU (300 kp of work at 50 rpm and 50 W). After the WU was completed, each pitcher was properly seated in the isokinetic dynamometer according to the Biodex System 3 Pro protocol. The testing was performed in the pitcher's selected range of motion (ROM), with each pitcher encouraged to achieve his full ROM in ER and IR on each repetition. Before testing, each pitcher performed 4 WU repetitions at 25, 50, 75, and 100% of their perceived maximal effort at each speed. Peak torque (PT) were collected from 5 maximal effort repetitions at 180°·s−1, from 10 maximal effort repetitions at 300°·s−1, and from 15 maximal effort repetitions at 450°·s−1. A 2-minute rest period was allowed between the test angular speeds. The non-dominant (ND) arm was tested first at each angular speed with the identical procedure performed on the dominant (D) arm immediately following. PT data were collected at each angular speed using the Biodex dynamometer and software. Data reduction and analysis were performed with MATLAB (R2012a). Means and SDs were calculated for PT, PT/body weight (BW), time rate to torque development (Torque 0.2 seconds), work/BW ratio, total work, work fatigue, average power, and ER/IR PT ratio. Repeated measures ANOVA were performed across all angular speeds followed by post-hoc tests if the main effects were significant. For each dependent variable of arm and angular speed, a repeated measure ANOVA was performed across ER and IR. Results: There were significant differences (p < 0.05) between ER and IR for all variables at all angular speeds within D and ND arms except work fatigue and average power. Additionally, except for work fatigue, there were significant differences (p < 0.05) of dependent variables among all angular speeds within ER and IR at both D and ND arms. ER/IR PT ratio for D and ND arms at 180°·s−1 were 0.70 and 0.79 (p < 0.001), at 300°·s−1 were 0.65 and 0.69 (p < 0.05), and at 450°·s−1 were 0.64 and 0.70 (p = 0.114), respectively. Conclusions: The difference between PT for D and ND arms of collegiate baseball pitchers was significant at all 3 isokinetic angular speeds. IR PT was significantly greater than ER PT at all angular speeds for D and ND arms. ER/IR PT ratios demonstrated significant differences between D and ND arms at 180 and 300°·s−1. ER/IR PT ratios remained relatively consistent throughout the speed spectrum and to previous research. Practical Applications: Data from this study can be used by those that train baseball pitchers to select exercises to specifically address the weaknesses identified by the dynamometer values. This way a proactive approach can be taken to strengthen the shoulder musculature and potentially avoid injury.

(39) Hip Abductor Strength Improvement Following a 10-Week Golf Program in Healthy, Older Adults

J. Moore,1 K. Kanwar,1 K. Lee,1 R. Hawkes,2 and G. Salem1

1University of Southern California; and 2The Golf & Health Project

It is important to identify safe, adherent exercise programs that can improve lower extremity strength in older adults to prevent fall risk. Golf is a multimodal exercise that involves walking long distances, bending and squatting movements, and high-power swings that could influence lower extremity strength. Purpose: The purpose of this study was to investigate if a 10-week golf program could elicit improvements in hip abductor strength in healthy, older adults. Methods: 15 healthy, older adults without previous golf experience were enrolled in a golf program with fitness testing before and after the intervention. One subject had to drop out of the study due to a work-related injury at week 8. Hip abductor strength was measured using a modified hip abductor dynamometer (Lee & Powers, 2013). Paired t tests were run to determine significance. Results are presented as percent change from pre-to post-measurement. Cohen's d effect sizes were calculated and reported as small = 0.2, medium = 0.5, and large = 0.8. Results: Subjects completed 283/300 (94%) sessions and there were no adverse events related to the golf program. Hip abductor strength increased by 7.3% with a large effect size (p = 0.005, d = 0.94). Conclusions: Golf includes multiple aspects of fitness and provides a safe and enjoyable form of exercise for older adults as seen by the high adherence to the program. Long walking distances, squatting, and golf swings provide sufficient loading to simulate improvements in hip abductor strength as well as other lower extremity fitness measures. These improvements are important when considering fall risk for older adults. Practical Application: Golf should be considered when exploring exercise programs for older adults. It provides the necessary loading to stimulate fitness improvements in older adults and offers a physical activity that may be more adherent than traditional exercise modalities. More work should be pursued to examine the efficacy of a golf program in other older adult populations, such as those with diabetes, dementia, and neurologic disease.

(40) Assessing the Validity and Reliability of Heart Rate Data Obtained Using a Smart Watch Prototype Device Against a Reference Standard

J. Gephart, G. Kelly, L. Barker, J. Siedlik, and R. Edmonds

Creighton University

Traditional heart rate monitors record heart rate (HR) using a chest-worn transmitter and are often able to provide ECG-level accuracy. However, photoplethysmography (PPG) is a relatively new wearable technology that has been introduced to the market and is starting to compete against traditional chest-worn HR monitors. The use of PPG sensors has enabled HR to be recorded at various anatomical landmarks apart from the chest, with devices now recording at the wrist and/or upper arm. However, with the abundance of new technology saturating the market, it is important to ensure these devices provide a valid and reliable indication of the variables they record. Purpose: To assess the accuracy of heart rate data recorded using a prototype smart watch heart rate monitor when compared against a reference standard Polar heart rate monitor. Methods: Subjects (N = 52; 33 male & 19 female) completed a series of activities (Table 1) with a 30 seconds transition between each activity. Subjects wore a prototype watch on their right wrist and a Polar H10 chest-strap transmitter (Polar Electro, Kempele, Finland) with heart rate recorded continuously during the protocol. Data processing and statistical analyses were performed in Matlab (MATLAB 2019a; Mathworks, Natick, MA). A Bland Altman plot was used to assess agreement between the prototype device and Polar H10 transmitter. Results: On average, a strong positive correlation (r = 0.91 ± 0.15; 95% CI [0.86–0.95]) was reported between the prototype device and the Polar chest-strap transmitter. The average mean difference between devices was reported to be −1.3 ± 6.8 b·min−1 (95% CI [−3.3 to 0.8]), while the average SD difference was 9.7 ± 4.7 (95% CI [8.4–11.2]). Conclusions: These results suggest that the prototype device over reports HR when compared against the reference standard HR monitor, when recording throughout a series of various activities. Practical Application: It is important for individuals to understand the potential shortcomings of heart rate information obtained from wearable technology, even more so given the increased popularity of such devices. Care should be taken when applying this information.

Table 1 - Activity testing protocol

(41) An Acute Bout of Resistance Training Decreases Symptoms of Depression in College-Aged Individuals

J. Sawyer,1 B. Gough,1 and P. Cacolice2

1Rhode Island College; and2Westfield State University

Although there is ample research examining the effects of aerobic exercise on mental health, research aimed at determining the effects of resistance training on depression and anxiety is limited. Purpose: The purpose of the current investigation was to determine if a single session of resistance training reduces self-reported symptoms of depression and anxiety in college-aged individuals. Methods: Subjects were recruited via campus advertisements and through face-to-face recruitment efforts. Individuals that met the inclusion criteria completed an informed consent, health history questionnaire and physical activity readiness questionnaire (PAR-Q). Subsequently, subjects completed a 3–5 repetition maximum test for the barbell back squat, barbell bench press and sumo style deadlift. Following the maximum testing session, subjects completed a balance/flexibility session and a bout of resistance training in random order. The flexibility/balance session consisted of dynamic stretches of all major joints throughout the body, star excursion test, lateral jumps, and heel-to-toe walks. The bout of resistance training consisted of 3 sets of 8 repetitions at 80% of the predicted one-repetition maximum for barbell back squat, barbell bench press, and sumo style deadlift. Accessory exercises (bicep curls, tricep extensions, lat pulldowns, reverse lunges) were performed for 3 sets of 10 repetitions at a self-selected weight. Before and after each session subjects completed a Beck Depression Inventory (BDI) and Beck Anxiety Inventory (BAI). The flexibility/balance session served as a control (C) and the resistance training session served as the experimental intervention (I). Results: There was a mean group difference between the net decrease in BDI score for the C vs. I conditions (p = 0.047), with the I group demonstrating a greater decrease in BDI scores. There was a statistically significant difference between the pre-test measures for the C and I groups for BDI (p = 0.021), but not the BAI (p = 0.159). This indicates that the individuals demonstrated different depression value scores prior to both tested conditions. There was no such difference in the BAI scores between C and I (p = 0.622). A post-hoc analysis indicated that the change in BDI scores between conditions resulted in a Cohen's d effect size of 1.166. Utilizing this value, the calculated post-hoc power was 999. Conclusions: The researchers determined that subjects reported a decrease in feelings of depression during both the C and I sessions. There was, however, a greater reduction after the bout of resistance training in BDI scores. The change in feelings of anxiety was not significant for either session. One possible cause for the decrease in feelings of depression in both sessions could be attributed to the Hawthorne effect. Conversely, subjects reporting a decrease in feelings of depression in both sessions could be attributed to an increase in body temperature after stretching and exercise. Practical Application: A single session of resistance training may be used to acutely manage feelings of depression in college-aged students.

(42) Athlete Load Monitoring During in-Season Women's Collegiate Basketball

D. Wong, J. Fields, F. Brown, R. Baker, and M. Jones

George Mason University

Derrick S. Wong,1,2,3 Jennifer B. Fields,1,2 Faith S.A. Brown,1 Robert E. Baker,1,3 and Margaret T. Jones1,2,3

1Frank Pettrone Center for Sports Performance, George Mason University, Fairfax, VA;2School of Kinesiology, George Mason University, Manassas, VA; and3Center for Sport Management, George Mason University, Fairfax, VA

Sport training requires a balance between periods of overload and recovery; therefore, monitoring internal and external athlete loads in training and competition are beneficial to prescribing training and tracking recovery. Previous athlete load research has addressed primarily men's field sports and thus, limited information exists for women's basketball. Purpose: To determine markers of internal and external athlete load during the 9-week period of conference play for all practices (n = 39) and games (n = 16). Methods: National Collegiate Athletic Association Division I women's basketball athletes (n = 6; mean ± SD age: 20.2 ± 0.4 years; body mass: 71.8 ± 9.1 kg; body height: 173.17 ± 9.28 cm; body fat: 20.1 ± 5.8%; V̇o2max: 42.1 ± 4.1 ml·kg−1·min−1) participated. For inclusion in data analysis, athletes played ≥15 minutes in 80% of the 16-game conference schedule. Internal load markers based upon heart rate (HR) response were measured using portable wireless HR monitors. These internal markers included training impulse (TRIMP), TRIMP per minute (TRIMP·min−1), and time spent in 5 HR zones based upon maximum HR percentage (%HRmax): (a) recovery (REC: 50–60% HRmax), (b) aerobic#1 (AZ1: 60–70% HRmax), (c) aerobic#2 (AZ2:70–80% HRmax), (d) anaerobic (ANZ: 80–90% HRmax), and (e) high intensity (HITZ: 90–100% HRmax). Markers of external load measured with GPS/GNSS technology included: total jumps (TJ), player load (PL), player load per minute (PL·min−1, and inertial movement analysis (high ≥3.5 m·s−2 (IMA high). Multiple analysis of variance was used to assess mean differences in all load variables for practices and games (p < 0.05). Results: Game measures were significantly higher than practice for internal load variables of TRIMP (p < 0.001), TRIMP·min−1 (p < 0.001), AZ1 (p = 0.002), AZ2 (p < 0.001), ANZ (p < 0.001), and HITZ (p < 0.001) as well as for external load variables of PL (p < 0.001), PL·min−1 (p < 0.000), IMA high (p < 0.001), and TJ (p < 0.002). External load measures of practice and game intensity and the ratio of practices to games are presented in Table 1 (mean ± SD). In practice, athletes performed 42% of game level IMA high efforts, 66% of game level PL·min−1, 43% of game level PL, and 58% of game level TJ. Conclusions: All athlete load markers were higher in games compared to practices. In order to avoid non-functional overreaching, promote recovery, and reduce the risk of injury, selected practices should be designed with the goal of achieving game load metrics. Practical Application: The monitoring of internal and external athlete load variables enables coaches to compare practice measures with game measures. Such comparisons may provide a better understanding of how specific drills and practice plans affect athletes as well as serve to inform training program design and implementation.

Table 1 - External measures of athlete load in practices, games, and the ratio between practices and games.

(43) Using Sleep Metrics to Predict Morning Heart Rate Variability During Congested and Non-Congested Seasonal Periods in Division 1 Field Hockey Players: a Regression Analysis

J. Ghigiarelli and V. Vogels

Hofstra University

Congested scheduling is defined as the scheduling of games played with <3 days recovery in between. As expected, the concern with congested scheduling is that athletes are exposed to high levels of fatigue, leading to decreased performance and increased injury risk. Two standard methods to monitor an athlete's daily fatigue during the season are morning heart rate variability (HRVWAKE) and objective sleep metrics. In the general population, research has found that an increase in HRVWAKE correlates with reduced sleep latency and fewer awakenings. A greater understanding of the relationship between these variables during intense seasonal demands can be useful to monitor and improve recovery among athletes. Purpose: The purpose of this study is to explore the relationship between HRVWAKE, using the natural logarithm root mean square sum of differences (lnRMSSD) score and objective sleep metrics in Division 1 field hockey players during congested and non-congested scheduling periods within the season. Methods: Daily monitoring for lnRMSSD and sleep were collected in 9 players for 70 days (congested 38 days, non-congested 32 days) for the 18-game season. A polar heart rate strap with a smartphone application measured lnRMSSD, and sleep metrics were measured using continuous wrist actigraphy. Five sleep performance metrics were used in the prediction model: sleep latency (SLAT), sleep efficiency (SEFF), wake after sleep onset (WASO), wake episodes (WEPI), and total sleep time (STIME). Backward regression models were calculated for congested and non-congested periods. Variables with p-values > 0.100 were excluded from the model. Results: Means and SDs for lnRMSSD during congested and non-congested scheduling were 4.53 ± 0.32 ms and 4.54 ± 0.41 ms, respectively. Three sleep scores significantly predicted lnRMSSD during congested scheduling: SLAT (p = 0.021, b1 = −0.004), WASO (p = 0.024, b2 = −0.004), and STIME (p = 0.054, b3 = 0.001) and 2 scores for non-congested, WASO (p = 0.01, b1 = −0.004), WEPI (p = 0.01, b1 = 0.037). Conclusions: These results suggest that HRVWAKE will increase with reduced SLAT and WASO times and will increase with higher STIME scores. The results of this study support previous research that sleep can affect cardiac autonomic activity and that specific sleep metrics can be used to predict HRVWAKE. Sleep was more sensitive to predicting HRVWAKE for congested compared to non-congested scheduling, and SLAT and WASO are the strongest predictors. Practical Application: Better sleep is a priority during times of congested scheduling when recovery time between games is reduced. Athletes who are looking to improve their HRVWAKE score can focus on optimizing better sleep strategies to reduce SLAT and WASO times.

(44) Relationship of Sleep and Perceived Effort in Collegiate Women Basketball Athletes

G. Cammarano, J. Fields, D. Wong, F. Brown, R. Baker, and M. Jones

George Mason University

Attainment of ideal sleep quantity and quality can be difficult for collegiate athletes due to the heightened demands of sport and academic schedules. Both sleep quantity and quality have been shown to inversely impact pre-training fatigue levels and post-training athlete perceived effort. Reduced sleep has been associated with decreased performance and a heightened risk of injury. However, no data exist for collegiate women athletes in regard to sleep quantity and quality and their impact upon athlete ratings of perceived exertion of exercise sessions. Purpose: To investigate the relationship between sleep quantity and quality and perceived exertion during pre-season training and in-season practices and games for collegiate women basketball athletes. Methods: National Collegiate Athletic Association Division I women basketball athletes (n = 14, mean ± SD age: 20 ± 1.53 years; body mass: 81.23 ± 18.7 kg; height: 177.08 ± 8.36 cm; body fat: 23.17 ± 7.66%) participated. Data were collected over a 3-month period that consisted of pre-season training (30 practices) and non-conference game play (30 practices, 13 games). Each day, immediately upon waking, athletes used their mobile phones to complete self-reported measures via an electronic questionnaire. The self-reported measures employed a Likert scale from 1 to 5 for sleep quality, and sleep quantity was reported as number of hours slept. Five minutes after each exercise session (i.e., practices, games), athletes reported their Rating of Perceived Exertion (RPE) using the Borg CR-10 Scale. The session's RPE was then calculated (RPE × training duration in minutes). One-way analysis of variance was utilized to assess differences in sleep quality and quantity during the pre-season and in-season (p < 0.05). In addition, multiple regression analyses assessed: 1) the relationship between sleep quality and quantity with sRPE for the pre-season and in-season periods and 2) the relationships between sleep quality and quantity with sRPE for games. Results: Sleep quality (p < 0.001) and quantity (p < 0.001) were lower in the pre-season (3.6 and 6.7 hours, respectively) compared to in-season (3.7 and 7.2 hours, respectively). Sleep quality and quantity were not associated with post-game or post-practice sRPE values during pre-season or in-season periods. Conclusion: Athletes reported improved sleep quality and quantity during in-season compared to pre-season. However, there was no relationship between sleep and sRPE. It is recommended that future research examine sleep and its association with other wellness self-reported measures as well as performance assessments. Practical Application: Improved sleep during high periods of competition is beneficial for achieving optimal performance, reducing risk of injury, and maintaining overall health. Since there was no relationship between sleep quality and quantity and sRPE, athletes may not perceive sleep to have an adverse impact on their game performance. Although sRPE has shown to be a strong indicator of training load, sleep perception may not play a role.

(45) Accelerometry and Global Navigation Satellite System Derived Loads

A. Bursais and J. Gentles

East Tennessee State University

Accelerometers and Global Navigation Satellite Systems (GNSS) have become popular wearable technologies used to monitor training load in sport. However, the relationship between accelerometry, GNSS and known distance, has not been thoroughly investigated. Purpose: The purpose of this study was to assess and compare the ability of accelerometry and GNSS to predict known distance completed using different movement constraints. Methods: Thirty physically active college students (height 176.8 ± 6.1 cm, weight 82.3 ± 12.8 kg) participated in this study. This investigation was approved by the Institutional Review Board and all subjects completed and signed a University-approved informed consent. Acceleration data was collected via a tri-axial accelerometer sampling at 100 Hz (Zephyr BioHarness v3, Zephyr Technology Corp., Annapolis, MD). Accelerometry derived metrics included the sum of the absolute values of acceleration (SUM), the square root of the sum of squared accelerations (MAG), Player Load (PL) and Impulse Load (IL). Distance (GNNSD) was measured from positional data collected using a triple GNNS unit sampling at 10 Hz (Titan Sensors 2, Houston, TX). The accelerometer was placed at the level of the xiphoid process, along the midsternal line, and the GNSS unit was fixed to the back of the subjects at the base of the cervical spine between scapulae. Each subject walked 2 different known distances (DIST); one distance around a 2 m diameter circle (small circle) and a different distance around an 8 m diameter circle (large circle). Each distance completed around the small circle by one subject, was completed around the large circle by a different subject. The same 30 distances were completed around each circle and ranged from 12.56 to 376.99 m. Circles were used to limit the influence of initiating movement and braking associated with changing direction. Data were transformed using the natural logarithms (LN) of DIST, SUM, MAG, PL, IL, and GNSSD. Separate simple linear regression models were created to assess the ability of each independent variable (SUM, MAG, PL, IL, and GNSSD) to predict DIST. Results: All regression models performed well (R2 = 0.922–0.999; RMSE = 0.047–0.242). GNSSD (small circle, R2 = 0.997, RMSE = 0.047; large circle, R2 = 0.999, RMSE = 0.027) the accelerometry derived metric MAG (small circle, R2 = 0.983, RMSE = 0.112; large circle, R2 = 0.995, RMSE = 0.064) performed best among all models. Conclusions: GNSS and accelerometry derived metrics are valid indicators of total distance when walking is performed under different movement constraints. Practical Application: This research illustrates that both GNSS and accelerometry derived metrics may be used to indicate total distance completed while walking. This may also suggest that both GNSS and accelerometry are equally capable of quantifying training loads associated with sport-related training and competition. Future research should investigate whether training load quantification is enhanced using a combination of GNSS and accelerometry, or whether a single sensor, GNSS or accelerometer, is more appropriate to quantify training loads in a sport that often includes changes of direction, jumping, contact, and straight-line movement.

(46) Cardiovascular Effects of Water and Sports Drink Ingestion: Implications for Heart Rate Variability Monitoring

M. Christiani and A. Flatt

Georgia Southern University

It is currently unknown if a sports drink differentially affects cardiac-autonomic and hemodynamic parameters relative to water ingestion. In addition, how long individuals should wait following fluid intake prior to acquisition of resting heart rate variability (HRV) for assessing training status is also unknown. Purpose: To determine the effects of water and sports drink ingestion on HRV, blood pressure (BP), strove volume (SV) and systemic vascular resistance (SVR) in trained males. Methods: Subjects (n = 10, age = 25.2 ± 3.9 years; height = 181.7 ± 8.5 cm; weight = 82.5 ± 13.2 kg) with at least 1 year of resistance training experience participated in this study. The protocol involved 3 trials where fasted subjects consumed 591 ml of water, 591 ml of a sports drink, or 10 ml of water (control) in random order. Trials were performed on 3 separate mornings within 14 days. Fluids were refrigerated to a temperature of 5° C. During each trial, the natural logarithm of the root mean square of successive R-R intervals (LnRMSSD, a parasympathetic HRV index) was obtained using a portable electrocardiograph sensor from 5-minute segments at pre-ingestion to serve as baseline, and again from 5 to 10 minutes, 25–30 minutes, 40–45 minutes, and 55–60 minutes post-fluid ingestion. BP, SV and SVR were obtained using a clinical automated continuous non-invasive arterial pressure device from the same 5-minute segments. Results: A condition × time interaction was observed for LnRMSSD (p < 0.05). LnRMSSD increased (p < 0.05) following water ingestion at all time-points relative to water baseline (Figure 1). No changes in LnRMSSD were observed for sports drink or control (p > 0.05). A main effect for time was observed for diastolic BP (p = 0.04). Diastolic BP at 40–45 minutes post-ingestion was greater than baseline (66.6 ± 6.8 vs. 71.9 ± 6.7 mm Hg, p = 0.03). No main effects were observed for systolic BP (p > 0.05). A main effect for time was observed for SV. SV at baseline (111.6 ± 15.4 ml) was greater than 40–45 minutes (104 ± 15.4 ml) and 55–60 minutes (105.4 ± 15.4 ml) post-ingestion (p < 0.05). Main effects for condition and time were observed for SVR (p < 0.05). SVR for water (1,079.2 ± 165.8 mm Hg·min·ml−1) was greater than sports drink (1,028.9 ± 166 mm Hg min·mL−1) and control (1,009.8 ± 166.9 mm Hg·min·ml−1) (p < 0.05). In addition, SVR at 40–45 minutes post-ingestion (1,087.2 ± 158.1 mm Hg·min·ml−1) was greater than baseline (969 ± 161.2 mm Hg·min·ml−1) (p < 0.05). Conclusions: Water ingestion increased HRV for at least 60 minutes whereas the sports drink had minimal effects. Pratical Application: Increased parasympathetic modulation of the heart following water ingestion is likely a result of baroreflex activation to maintain BP in the face of increased SVR. When using HRV to monitor athletes, practitioners must control for recent water ingestion. HRV measures performed within 1 hour of 591 ml water ingestion will be inflated, thereby obscuring interpretations of recovery status.

F15
Figure 1.:
Condition by time interaction plot for LnRMSSD.

(47) Performance Characteristics in High Intensity Training Athletes

M. Whitehead, R. Whitehead, W. McHenry, B. Sizemore, and V. Mortezazadeh

Stephen F. Austin State University

Purpose: The purposes of the study were to: (a) Examine differences in performance characteristics (Functional Movement Screen (FMS) scores, strength, power, and dynamic exercise performance) between male and female high intensity training (HIT) athletes, and (b) Determine if correlations between Functional Movement Screening (FMS) scores and the ability to perform strength, power, and dynamic exercise in a cohort of male and female HIT athletes. Methods: A total of 30 subjects (males, n = 15; and females, n = 15) (mean ± SD, age = 30.7 ± 9.9 years) with minimum two-years of HIT experience were recruited to participate in this study. On the first day of data collection, each subject's height and weight was measured, followed by body composition measurement (7-site skinfold), FMS screening, and 1-Repetition Maximal (1-RM) lifts for deadlift (DL), shoulder press (SP), and power clean (PC). A minimum of 5 days later each performed a standardized test of dynamic exercise (DE) that involved performing as many repetitions as possible of 5 pullups, 10 pushups, and 15 unloaded squats in 20 minutes. Mann-Whitney U tests were performed to compare differences between the males and females for FMS scores and ANOVA was used to determine differences between the males and females for all other variables. Pearson Product-Moment correlation was used to determine relationships between variables. Statistical significance was set at p £ 0.05 for all analysis. Results: FMS score analyses indicated that the females, as compared to males, had higher straight leg raise (SLR) scores (2.9 vs. 2.1, p = 0.001) and sum of all scores (FMSSUM) (16.9 vs. 15.4, p = 0.045). Males, as compared to females, demonstrated greater muscular strength per kilogram of body weight on the DL (1.99 vs. 1.65 kg·kgBW−1, p = 0.007) and the SP (0.833 vs. 0.513 kg·kgBW−1, p < 0.001) exercises. Males also demonstrated greater muscular power per kilogram of body weight on the PC (1.146 vs. 0.766, p < 0.001) exercise as compared to their female counterpart. There was no statistically significant difference between groups for DE. A significant inverse relationship was shown to exist between shoulder mobility (SM) and SP kg·kgBW−1 (p = 0.047 and r = −0.365), and SM and PC kg·kgBW−1 (p = 0.040 and r = −0.377). There was no significant correlation found between FMS and DE. Conclusions: A significant difference between males and females was observed in the SLR, indicating that the males had a deficit in dynamic hip mobility and core stability. Considering no other differences were demonstrated between the specific tests of the FMS, it is plausible that the difference in SLR may account for the overall difference observed between FMSSUM scores. Although differences were shown between males and females for both strength and power, there were no differences with dynamic exercise. Practical Application: The findings of this study support the use of the FMS in the evaluation of athletes who are training for maximal muscular strength and power, but not for performance outcomes using dynamic exercise as a criterion measure. In addition, gender differences should be considered when designing training programs for maximal muscular strength and power training. Finally, there is a need for greater hip mobility and core stability training in male athletes.

(48) Agreement Between A Bluetooth Finger Sensor and Electrocardiography for Determining LNRMSSD

B. Hornikel,1 C. Holmes,2 M. Fedewa,1 and M. Esco1

1The University of Alabama; and2Washing University School of Medicine

Heart rate variability (HRV) is a measure of the autonomic nervous system that can be used as an objective indicator of recovery and readiness to perform in athletic populations. Electrocardiography (ECG) is the criterion measure for assessing HRV. With improvements in smartphone technology, there has been a greater push for more mobile methods for monitoring athletes' recovery in field-settings. A novel Bluetooth pulse finger sensor (BPFS) provides a possible simplistic and cost-effective alternative to traditional ECG measures, however has yet to be extensitvely validated. Purpose: The purpose of this study was to determine the agreement between a BPFS and ECG for measuring ultra-short-term heart rate variability in 3 different body positions. Methods: Thirty subjects (19 males and 11 females) were recruited from the University of Alabama Division-1 swim team (age = 20.9 ± 1.65 years, height = 184.13 ± 9.78 cm, weight = 80.65 ± 11.95 kg) to participate in this study. Heart rate data were obtained using the CorSense BPFS and an ECG criterion in a quiet, climate-controlled room. The BPFS was placed on the left index finger of the subject and connected to an iPad2 (Apple Inc, Cupertino, CA) via Bluetooth 4.0 to the EliteHRV smartphone application (EliteHRV, Asheville, NC). The ECG data were collected using a BIOPAC MP150 BioNomadix Wireless system (BIOPAC System, Inc., Goleta, CA). Following a stabilization period, simultaneous measures were taken with the BPFS and ECG for 60 seconds. Measurements were taken in 3 body positions: supine, seated, and standing. The BPFS provided a root mean square of successive RR differences (RMSSD) value which was then log-transformed (LnRMSSD). The ECG data were analyzed using KUBIOS HRV Premium (Kubios, Kuopio, Eastern Finland). Paired-samples t-tests were used to examine potential mean differences between the HRV measures in each body position. Bivariate correlations between HRV measures were assessed using Pearson's r. The Bland-Altman method was used to determine the level of agreement as the 95% confidence interval of the constant error (CE±1.96*SD). Data reported as mean ± SD, with p < 0.05 used to determine statistical significance. Results: Medium to large differences were observed between BPFS and ECG, such that BPFS measures were significantly different LnRMSSD across all body positions: supine (4.35 ± 0.70 vs. 4.12 ± 0.73, ES = 0.32, p = 0.007), seated (4.31 ± 0.64 vs. 3.74 ± 0.62, ES = 0.90, p < 0.001), and standing (3.42 ± 0.65 vs. 3.03 ± 0.81, ES = 0.53, p = 0.001), respectively. According to the Bland-Altman method, the level of agreement between the HRV methods in each body position, supine (−0.20 ± 2.70), seated (0.05 ± 1.41), and standing (0.10 ± 0.74). Correlations were very large between BPFS and ECG in supine and standing (r = 0.82 and 0.76, respectively, p < 0.001), and moderate for seated (r = 0.31, p = 0.107). Conclusions: Correlations between BPFS and ECG ranged from moderate to very large (r = 0.31–0.82). However, significant differences were observed when comparing ECG and BPFS in all 3 body positions and effect sizes ranged from medium to large (ES = 0.32–0.90). Practical Application: The CorSense BPFS offers a practical means of using a smartphone application to measure HRV in field settings. However, BPFS produces significantly different LnRMSSD when compared to the criterion ECG in supine, seated, and standing positions. Based on the results of this study, practitioners should use the BPFS with caution

(49) A Pilot Analysis of the Influence of Lower-Body Strength and Power During Law Enforcement Tasks Under Load

A. Bloodgood,1 M. McGuire,1 J. Dawes,2 R. Orr,3 J. Dulla,3 and R. Lockie1

1California State University, Fullerton;2Oklahoma State University; and3Bond University

Introduction: Many law enforcement agencies require recruits to complete assessments that test their underlying fitness characteristics as they relate to job tasks. These tests are administered without personal protective equipment (PPE typically 8–10 kg of added external load). PPE load could lead to a decrease in task performance. In this pilot study the decrease between unloaded and loaded performance is referred to as the tactical deficit. Lower-body strength and power could mitigate the tactical deficit created by PPE. Purpose: To examine the effects of load carriage during policing tasks and investigate whether dynamic and isometric lower-body strength or power can lessen the tactical deficit. Methods: Ten college students (7 males, 3 females) from one university were recruited and age-matched to typical law enforcement recruits. This pilot study comprised of 3 sessions across 3 days. Session 1 consisted of a standing broad jump (SBJ), isometric leg/back dynamometer (LBD), and a one-repetition maximum hexagonal bar deadlift. In sessions 2 and 3, subjects completed 4 police tasks either loaded or unloaded: a vertical jump, 75-yard pursuit run (75 PR), a 9.75-m body drag (BD), and a 500-yard run. In the loaded condition, subjects wore 8–10 kg of mandated officer PPE. Additionally, a vertical jump in the unloaded condition was included as part of the power measures. Dependent t-tests calculated differences in unloaded and loaded condition times (p < 0.05). Tactical deficit was then calculated, which was expressed as an absolute value percentage difference via the formula: (loaded time ¸ unloaded time × 100) − 100. Partial correlations controlling for sex analyzed relationships between relative and absolute isometric and dynamic strength (LBD and hexagonal bar deadlift, respectively), SBJ, and vertical jump height and peak power (PAPw), derived from jump height, with the tactical deficit for each of the police tasks. Results: There were significant differences in performance between the unloaded and loaded conditions for the vertical jump (∼7.53 cm lower jump height, p < 0.001, tactical deficit = 13.02 ± 6.25%), 75 PR (∼0.92 seconds slower, p = 0.03, tactical deficit = 5.11 ± 6.53%), and the 500-yard run (∼12.05 seconds slower, p = 0.01, tactical deficit = 13.09 ± 13.20%). No significant differences were found for the BD (∼0.42 seconds slower, p = 0.36, tactical deficit = 11.16 ± 19.06%), although the loaded performance was slower. There was a moderate negative relationship between 75 PR tactical deficit with VJ height (r = −0.62, p = 0.01) and PAPw (r = −0.65, p = 0.05). For absolute LBD, there was a large negative relationship for tactical deficits with 75 PR (r = −0.78, p = 0.01) and a moderate negative relationship with BD (r = −0.67, p = 0.04). For relative LBD, there was a large negative relationship with 75 PR tactical deficits (r = −0.75, p = 0.01). Conclusions: This pilot analysis showed that PPE typically decreased performance when completing police tasks. Subjects that were more powerful had a lower tactical deficit in the 75 PR, which is a job task that requires explosive power for efficient execution. Greater lower-body isometric strength also appeared to mitigate the tactical deficit in the BD and 75 PR. Practical Application: This data suggests law enforcement training staff should focus on developing lower-body strength and power to sustain the demands of PPE and decrease the tactical deficit in foot pursuit and dragging tasks.

(50) Do Baseline Physical Fitness Measures Predict Police Academy Graduation?

J. Martin, J. Merrigan, and D. Marks

George Mason University

Police officers experience high levels of stress and as a result the required police academy is aimed to train recruits to handle physical and psychological stressors. Police departments undertake a large financial commitment with estimated costs reaching upwards of $100,000 per recruit. Since initial fitness testing is typically required it would be valuable to understand which fitness components may predict the likelihood of graduation from the academy. However, existing data is limited. Purpose: To retrospectively analyze baseline academy recruit fitness data, from 7 recruit classes, to study the relationship of fitness components with academy graduation rates. Methods: Recruits (146 males, 46 females) completed initial academy fitness testing between 2016 and 2019. The following testing battery was performed over the course of an entire day to ensure adequate recovery between tests: one repetition maximum bench press (upper-body strength), push-ups to failure (upper-body pushing endurance), sit-ups to failure (core endurance), pull-ups to failure (upper-body pulling endurance), sit and reach (low-back and hamstring flexibility), and a 1.5-mile run (aerobic capacity). Correlation coefficients were used to assess relationships among variables. Backward logistical regression analysis was performed to determine the best group of fitness components for predicting graduation rates (p < 0.05). Results: Males had greater performances in all fitness components except for similar sit-ups and lower sit and reach (Table 1). Moderate positive correlations existed between push-ups and sit-ups (r = 0.56, p < 0.05) as well as body mass and bench press (r = 0.57, p < 0.05). Sit-ups (r = −0.59, p < 0.05) and push-ups (r = −0.51, p < 0.05) had moderate negative correlations with 1.5 mile run times. The regression model including sex, push-ups, and pull-ups explained 14.4% of the variance in pass/fail rates, χ2 (2) = 10.139, p = 0.025. Males were 4.67 (p = 0.030) times more likely of graduating and those with increasing push up scores were 0.95 (p = 0.031) times less likely to pass, while pull ups were not significant (p = 0.100). Conclusions: Greater performances on one fitness test did not predict the likelihood of police academy graduation. Therefore, emphasis may be needed in areas across all fitness components. Further, in consideration of the greater fitness performances by males and their higher graduation rates, females may benefit from individualized training programs prior to academy entrance. Practical Application: Since no previous study evaluated this testing battery, and academies differ in fitness testing and passing rates, further research is needed to understand the role of fitness components on police academy graduation rates. Additionally, including the reason for unsuccessful policy academy graduation (fitness, injury, academic, or personal) is recommended for future research on this topic.

Table 1 - Sex comparisons on Entry-Level Police Academy Physical Fitness Assessment.

(51) The Influence of Percent Body Fat on Fatigability in Career Firefighters

K. Kennedy,1 M. Laffan,1 A. Trivisonno,1 G. Gerstner,2 J. Mota,3 H. Giuliani,1 P. Chen,4 and E. Ryan1

1University of North Carolina at Chapel Hill;2Old Dominion University;3University of Alabama; and4The University of North Carolina at Chapel Hill

Work-related fatigue can be linked to the majority of the fatal and non-fatal injuries in the fire service. Firefighters are susceptible to work-related fatigue due to long and strenuous shiftwork, which may be exacerbated in obese firefighters. Future controlled laboratory studies are needed to examine the influence of obesity on fatigability in career firefighters. Purpose: To investigate the influence of body fat percentage (%BF) on fatigability in male career firefighters. Methods: Forty-one healthy, male career firefighters (age: 32.34 ± 8.20 years, stature: 178.34 ± 7.89 cm, mass: 92.25 ± 18.74 kg, %BF: 24.08 ± 7.88%) with no recent (≤3 months) lower extremity injuries or surgeries visited the laboratory on one occasion following an 8 hour fast. Subjects refrained from caffeine and tobacco use and lower body exercise for at least 12 and 48 hours prior to testing, respectively. Subjects' %BF was measured using a dual energy x-ray absorptiometry (DEXA) scanner. Subjects were then familiarized with the lower body isometric strength and isotonic fatigue protocols with their dominant limb. Following a 10-minute rest period and standardized meal, subjects completed a maximal strength and fatigability assessment of their leg extensor muscles on a calibrated dynamometer. Following 3 warm-up isometric contractions (50–75% of their perceived maximum effort), subjects performed 3 isometric maximal voluntary contractions (MVC) separated by a 2-minute rest period. Subjects then performed 30 repeated isotonic contractions (1 repetition every 3 seconds) at 40% of their MVC from a starting position of 90° of flexion to 10° of flexion (0° = full extension) to assess leg extensor fatigability. The dynamometer passively returned the leg at a velocity of 45°·s−1 following each repetition. Immediately following the fatiguing protocol, subjects performed an additional MVC. All signals were sampled at 2 kHz and low-pass filtered with a fourth order, zero phase shift Butterworth filter using a 150 Hz cut-off frequency. Fatigability was quantified as the % reduction in peak torque (%∆PT) from pre-to post-fatiguing bout. A Pearson product-moment correlation coefficient was used to analyze the relationship between %BF and %∆PT, in addition to a partial correlation controlling for age. Alpha level was set a priori to 0.05. Results: Higher %BF was related to greater %∆PT (r = 0.406, p = 0.009) and similar relationships were found after controlling for age (r = 0.355, p = 0.027). Conclusions: Our findings suggest that firefighters with higher levels of %BF have greater fatigability during short duration (∼90 seconds), repetitive, high-intensity efforts. Practical Applications: Work-related fatigue is a critical issue in the fire service, and our findings highlight the negative impact of high levels of %BF on fatigue resistance. These findings are important given previous reports indicating firefighters are more overweight and obese than the general public. Worksite interventions targeted at improving body composition are critical within this population to enhance work performance. Future studies are needed to mechanistically determine why obesity impacts fatigability and subsequent performance in firefighters.

(52) Effects of Experience Upon Physiological Demands of Soldiers Performing Simulated Occupational Tasks

B. Cohen, J. Redmond, C. Haven, S. Foulis, M. Canino, P. Frykman, and M. Sharp

United States Research Institute Environmental Medicine

The U.S. Army has identified job-specific critical physically demanding tasks (CPDTs), many of which are common among most military occupational specialties (MOS)/jobs. Soldiers with more experience may execute CPDTs with less physiological demands. Purpose: To measure the impact of job task experience (time spent deployed, time in service, time in MOS/job) on physiological (heart rate [HR], oxygen consumption [V̇o2], and rate of perceived exertion [RPE]) demands of performing these CPDTs. Methods: Male combat arms Soldiers along with female Soldiers from other (non-combat arms) high physically demanding MOSs/jobs, were recruited to perform the following simulated CPDTs; ruck marching, sandbag fill/carry, combat rushes, evacuating a casualty, and dragging a casualty to safety. Demands were specifically recorded by Borg RPE scales (for RPE), Polar HR monitor (mean and post task HR), and portable Oxycon device (for oxygen consumption). Soldiers self-reported (via survey) their experience with the CPDTs. Linear regression models examined the association between measures of experience (independent variables) and physiological performance demands (dependent variables), adjusted by age, sex, height, and weight. Results: A total of 237 Soldiers (64% male), with an average age of 23.33 (±4.19) years, and an average 2.7 (±2.66) years in military service were included for analysis. Of all the models evaluated, significant associations included the impact of “time spent deployed” on the physiological measures of road march task performance (MeanHR F = 7.97, p = 0.018, β = −5.98; PostHR F = 24.84, p < 0.0001, β = −9.65), of the sandbag fill and carry tasks (Fill: PostHR F = 8.26, p = 0.005, β = −2.83; Carry: MeanHR F = 7.51, p = 0.007, β = −1.12) as well as the casualty drag task (PostHR F = 5.82, p = 0.017, β = −1.51). Road march performance physiological measures were also associated with “time in MOS” (MeanHR F = 8.25, p = 0.017, β = −2.66; PostHR F = 18.08, p=< 0.0010, β = −2.23) and “time in military service” (PostHR F = 12.85, p = 0.002, β = −1.25). Conclusions: Experience, defined as time spent deployed, time in military service and time in MOS/job, was associated with an impact on physiological task performance. For example, time spent deployed was associated with a 6 b·min−1 decrease in MeanHR and a nearly 10 beat/minute decrease in PostHR on the road march task for every increasing year deployed. Practical Application: Increasing task familiarization experience (presumably obtained through longer time deployed, time in MOS/job, or time in military service) may result in reductions of physiological task exertion.

(54) Physical and Mental Components of Quality of Life in Career Firefighters

G. Gerstner,1 M. Laffan,2 A. Trivisonno,2 P. Chen,3 H. Giuliani,2 J. Mota,4 and E. Ryan2

1Old Dominion University;2University of North Carolina at Chapel Hill;3The University of North Carolina at Chapel Hill; and4University of Alabama

The Veterans RAND 12-item Health Survey (VR-12) is a common health-related quality of life (QOL) measurement in the United States. While standard scores exist for the general population, it is unclear how career firefighters score on the physical (PCS) and mental (MCS) components of the VR-12 and whether these scores relate to other health-related variables. Purpose: The purpose of this study was to examine the influence of physical activity, percent body fat (%BF), age, and workability with VR-12 scores (PCS, MCS) in career firefighters, while comparing the PCS and MCS scores with the general population standards. Methods: Sixty healthy male career firefighters (age: 31.7 ± 7.4 years; stature: 179.0 ± 7.6 cm; mass: 92.5 ± 26.8 kg; BMI: 28.0 ± 5.0 kg·m−2) volunteered for this investigation. Subjects were screened for health conditions (i.e., diabetes, hypertensions, asthma, heart disease, depression) using a health history questionnaire. Subjects who had any health conditions or major symptoms of disease were not included in the study. Resistance training status, workability, and QOL were self-reported. Subjects were instructed to come in 8 hours fasted (except water) prior to testing. Dual-energy X-ray absorptiometry was used to assess %BF. Resistance training workload (RT = days × minutes × intensity), and MCS and PCS from the VR-12 (custom algorithm) were calculated. Workability was scored on a 0–10 scale (0 = completely unable to work; 10 = work ability at its best). Pearson's product-moment correlation coefficients were used to examine the relationship between the VR-12 components (PCS, MCS) and %BF, RT, age and workability. Independent sample t-tests were used to compare PCS and MCS of the sample to standards in a “no conditions” population. Cohen's d effect sizes were calculated for each t-test. An alpha of p ≤ 0.05 was used to determine statistical significance. Results: There was a significant correlation between PCS and %BF (r = −0.275, p = 0.033), and RT (r = 0.266, p = 0.040). There were no correlations between PCS and age or workability (r = −0.010 to 0.211, p = 0.106–0.925), or between MCS and %BF, RT, age, or workability (r = −0.107 to 0.191, p = 0.144–0.575). PCS (53.7 ± 5.6; p < 0.001; d = 0.54) was significantly greater than the standard (49.7 ± 8.9) whereas MCS (53.2 ± 8.1; p < 0.001; d = 0.34) was significantly lower than the standard (55.8 ± 6.8). Conclusions: These findings suggest that lower body fat and higher RT workloads, but not age or workability, are related to a greater score on the physical component of health-related quality of life in career firefighters. Furthermore, our sample of firefighters self-reported greater physical QOL, but lower mental QOL than the general population. Practical Application: Wellness programs designed to improve adiposity and resistance training status may improve physical QOL for firefighters. Our sample of firefighters was healthy yet reported lower mental QOL than the general population. Given that mental health is a major component to wellness, it is critical that it be integrated into wellness programs to improve mental QOL in this population.

(55) Analysis of Quadriceps and Hamstring Isokinetic and Isometric Strength in Army Reserve Officer Training Corps (ROTC) Men and Women

J. Merrigan, K. O'Toole, C. Wutzke, and M. Jones

George Mason University

The incidence of lower extremity injury in Reserve Officer Training Corps (ROTC) cadets is 10% greater for women and the majority occur at the thigh or knee. Since, likelihood of injury may be dependent upon absolute muscle strength and asymmetries among muscle groups, evaluation of quadricep and hamstring function is imperative. In consideration of physiological and functional sex differences between men and women, it is central to identify potential areas of risk. Purpose: To evaluate sex differences in quadriceps and hamstring strength of ROTC cadets. Methods: 26 Army ROTC cadets (women, n = 12, age = 21 ± 2 years; men, n = 14, age = 21 ± 3 years) performed unilateral isokinetic knee extensions at 60°·s−1, 180°·s−1, and 360°·s−1 with continuous maximal effort from 10° to 90° knee flexion. Concentric (CON60, CON180, CON360) and eccentric (ECC60, ECC180, ECC360) actions were performed. At each speed, 3 practice repetitions (reps) (50–75% maximal effort) were allowed, followed by 30 seconds of rest, prior to 3 trial reps. Next, cadets performed 3 maximal voluntary isometric knee extensions at 60° of knee flexion with 1-minute rest between reps. No asymmetries existed between limbs, so performances were averaged across limbs with the greatest peak torque and total work within each measure used for analysis. Functional concentric hamstring to eccentric quadricep ratio as well as isometric hamstring to quadricep ratio were calculated using peak torque. Multifactorial analyses of variance were used to evaluate the main effects of sex and sex*speed*action*muscle interaction (p < 0.05). Results: Sex differences were present when evaluating the entire protocol for peak torque (women, 101.8 ± 31.6 N; men, 144.4 ± 41.7 N p < 0.001) and total work (women, 80.4 ± 30.7 Nm; men, 117.8 ± 35.1 Nm; p < 0.001). There was a sex*speed*action*muscle interaction for torque (p < 0.001) and work (p < 0.001). Men produced greater peak torque and total work for all eccentric actions, as well as greater peak torque and total work for flexors and extensors during CON60 and peak torque of flexors during CON360 (p < 0.05). Greater peak torque was observed during quadriceps compared to hamstrings for ECC60 (women, p = 0.011; men, p = 0.001) and ECC180 (women, p = 0.016; men, p = 0.049). Both men and women produced greater torque and work during eccentric compared to concentric actions (p < 0.05), and the differences between actions were greater at faster speeds. When collapsed across speeds, no differences existed in functional hamstring to quadricep ratios of peak torque (women, 1.63 ± 0.80; men, 1.55 ± 0.84; p = 0.602), total work (women, 2.54 ± 2.28; men, 2.32 ± 1.58; p = 0.625), or isometric hamstring to quadricep ratio (women, 0.55 ± 0.10; men, 0.54 ± 0.10, p = 0.922). Further, functional hamstring to quadricep ratio at 60°·s−1 was less than 360°·s−1 for women (60°·s−1, 0.98 ± 0.29; 360°·s−1, 2.31 ± 0.77) and men (60°·s−1, 0.95 ± 0.23; 360°·s−1 2.19 ± 1.10; p < 0.001). Conclusions: Strength differences between men and women are greater during eccentric actions. Yet, relatively, women produce more torque during eccentric compared to concentric actions and have similar hamstring to quadricep ratios as men. Thus, asymmetries may not exist across limbs or muscle groups within Army ROTC cadets. Practical Application: Since Army ROTC men and women did not differ in relative strength between muscle groups, but had larger differences in absolute eccentric strength, women cadets may benefit from eccentric training methods.

(56) Sisters in Arms: Between-Sex Differences in the Army Physical Fitness Test in ROTC Cadets

C. Caron-sabala,1 M. McGuire,1 J. Dawes,2 J. Scraper,2 and R. Lockie1

1California State University Fullerton; and2Oklahoma State University

Introduction: The Reserve Officer Training Corps (ROTC) is a high school and college program used to prepare young adults for enlistment in the US military. ROTC requires its subjects to undergo specific training to prepare them for commissioning. Although the US Army will change their physical fitness testing protocol to the Army Combat Fitness Test (ACFT) to determine eligibility for commission, historically the Army Physical Fitness Test (APFT) has been used for this purpose. The APFT consists of 2 minutes of push-ups, 2 minutes of sit-ups, and a timed 2-mile run. Many ROTC programs still rely on the APFT to assist with programming for physical training. There is little research indicating any differences among male and female ROTC cadets, and how this may vary between raw and scaled scores. This is important, especially considering that the testing may have an impact on females since the new ACFT test is not scaled like the APFT. Purpose: To determine the differences between male and female ROTC cadets on the APFT. Methods: Retrospective analysis of data from 67 ROTC cadets (49 male, 18 female) from a Midwestern school was conducted. Cadets completed the APFT on 4 occasions in one year, with the first being for diagnostic purposes, and the last for record; these were considered for this study. The raw score for push-ups, sit-ups, and the 2-mile run, the scaled score for each test, and the total APFT score were analyzed. The first test provided a baseline for analysis, and the last test determined if significant differences between change scores occurred by sex over the course of the ROTC program. Independent samples t-tests (p < 0.05) compared the males and females in the first and last scores for the APFT. Results: Significant between-sex differences were found in the first testing occasions for all scores (p ≤ 0.048), with males superior in all tests. In the last test, significant between-sex differences were only seen for the raw push-up, raw and scaled sit-up, and the 2-mile run raw scores (p ≤ 0.010). There were no significant differences between the scaled push-up or the scaled 2-mile run score in the last test for record, nor was there a significant differences in total APFT score (p ≥ 0.065). However, male cadets still demonstrated higher mean values for the scaled push-up score (81.92 ± 13.60 vs. 78.78 ± 15.83) and 2-mile run score (76.92 ± 20.79 vs. 70.94 ± 19.16). Male cadets also generated higher mean values in the overall APFT score (244.00 ± 43.84 vs. 220.39 ± 51.13). Conclusions: There were significant between-sex differences in raw scores for both APFT tests analyzed, with men having higher scores. Since the scores in the APFT are scaled relative to age and sex, female cadets were less affected in this data, and the scaled scores for the test for record were not different. However, for the ACFT, the scores will not be scaled relative to age or sex. If female cadets have lesser performance on these tests, it may put them at a physical disadvantage for career promotion compared to males. Practical Application: Female ROTC cadets demonstrated lower fitness in the APFT, which could be compounded further by the future ACFT. Female cadets may need specific strength and conditioning programs to pass the current APFT still used by many schools, and future ACFT. This would increase the probability for female cadets to tolerate the demands of commissioning into the US Army.

(57) Utilization of the 30-15 Intermittent Fitness Test and Individualized Interval Training Program With Law Enforcement Cadets

G. Martinez,1 X. Ma,1 S. Best,1 B. Johnson,2 and M. Abel1

1University of Kentucky; and2School of Health Sciences and Practice, New York Medical College

The importance of physical fitness in occupational performance in law enforcement officers is well documented. Law enforcement recruits are required to complete an academy training program to enhance occupational readiness. However, in a retrospective investigation evaluating the physical fitness outcomes of cadets in a state funded criminal justice training academy, it was noted that strategies to improve aerobic and anaerobic capacities were warranted. Purpose: To assess the effectiveness of the 30-15 intermittent fitness test (30-15 IFT) and shuttle run program to improve aerobic endurance and anaerobic capacity in law enforcement cadets and assess its relationship with other traditional fitness and occupational test outcomes. Methods: A convenience sample of 54 male (28.2 ± 6.9 years, 181.1 ± 6.9 cm, 95.0 ± 17.6 kg) and 9 female cadets (25.4 ± 2.5 years, 165.1 ± 6.6 cm, 65.3 ± 10.2 kg) representing 2 academy classes of a state funded training academy participated in this study. The control group (n = 32) followed standard care training practices during the 17-week program. The experimental group (n = 31) completed the 30-15 IFT at 3 time points (Wk: 1,8,16) with the final 30-15 IFT velocity serving as maximal aerobic running velocity (VIFT), which was used to design a periodized shuttle run program. Anthropometrics, a fitness battery (1.5 mile run, sit-ups, push-ups, one-repetition maximum bench press, and 300 m run) and an Occupational Physical Ability Test were evaluated at 3 time points of the training academy (entrance, midpoint, and exit). A 3 × 2 mixed factor repeated measures ANOVA was used to compare changes between groups and over time. T-tests where used for post-hoc analysis. Correlations and a stepwise multiple linear regression analysis were performed to determine the relationship between VIFT measures and all other physical fitness data. Session rating of perceived exertion (sRPE) was utilized to monitor daily training loads. The change in fitness outcomes across the time points was calculated relative to the baseline value: (% Difference = posttest value − entrance value)/entrance value) × 100). The level of significance was set at p < 0.05 for all statistical analyses. Results: There were significant improvements in 300 m run time (F (2,118) = 47.4, p < 0.01, ηp2 = 0.44, Power = 1.0) and 1.5 mile run time (F (2,118) = 115.1, p < 0.01, ηp2 = 0.66, and power 1.0) in both groups, however, there were no significant group differences (p = 0.42 and p = 0.06, respectively). VIFT was significantly correlated to BW (r = −0.41), sit-ups (r = 0.52), 300 m run (r = −0.71), 1.5 mile run (r = −0.83), push-ups (r = −0.76), and OPAT completion time (r = −0.71). BW and 1.5mile run time significantly predicted VIFT performance (F (2,27) = 37.7, p < 0.01, r2 = 0.73, SEE = 1.0). Aerobic sRPE training loads were significantly lower in the experimental group versus the control group (ENT-MID & MID-EXIT, p < 0.01). Conclusions: Although there were no significant differences between the groups, the 30-15IFT and subsequent shuttle run program yielded similar improvements in 300 m and 1.5 mi run outcomes with lesser training stress. Furthermore, correlational and regression analysis indicated that the VIFT measurement may be an appropriate metric to assess occupational performance in law enforcement cadets. Practical Application: The 30-15IFT and the individualized shuttle run program can be utilized in police academies to improve aerobic endurance and anaerobic capacity in cadets.

(58) Relationship Among Physical Activity Intensities, Obesity, and Cardiorespiratory Fitness in Career Firefighters

M. Perumal,1 S. Kopp,1 E. Hutcheson,1 M. Carper,1 N. Dicks,2 T. Walch,3 and A. Barry1

1Pittsburg State University;2Concordia College; and3University of North Dakota

Sudden cardiac death is the leading cause of death in career firefighters. Preliminary research has shown that, on average, firefighters meet the general population recommendation for physical activity (PA). However, they are more likely to be overweight or obese. Purpose: To examine relationships among objectively measured PA intensities, percent body fat (%BF), percent fat-free mass (%FFM), and cardiorespiratory fitness (CRF) in career firefighters. Methods: Firefighters from a Midwest fire department participated in the study. Measures included: dual energy x-ray absorptiometry (DEXA) to assess %BF and %FFM and an accelerometer to measure PA intensities (sedentary, light (LPA), and moderate-to-vigorous (MVPA)) while on- and off-duty. Firefighters wore accelerometers for their entire 12-day tour (e.g., 24-hours on, 24-hours off, 24-hours on, 48-hours off, 24-hours on, 24-hours off, 24-hours on, and 4 days off). Additionally, firefighters completed a stage-graded treadmill test replicating on-duty tasks in their bunker gear (e.g., pants, jacket, and boots) to determine maximal oxygen uptake (V̇o2max). Pearson Product-Moment Correlations assessed the relationship among physical activity intensities, obesity, and CRF. Results: Fourteen firefighters (age: 34 ± 6.5 years; %BF: 24.8 ± 3.9; %FFM: 75.9 ± 2.4; V̇o2max: 40.3 ± 4.7 ml·kg·min−1; sedentary: 541.4 ± 79.9 min·d−1; LPA: 338.7 ± 64.6 min·d−1; MVPA: 34.1 ± 19.4 min·d−1) completed the study. PA intensities were not significantly correlated with V̇o2max: sedentary (r = −0.26, p = 0.36), LPA (r = 0.23, p = 0.43) and MVPA (r = 0.33, p = 0.24). %BF (r = −0.30, p = 0.31) and %FFM (r = 0.50, p = 0.07) were not significantly associated with V̇o2max. Conclusions: Although the data does not demonstrate significant correlations between any measures, it does demonstrate a moderate positive, yet non-significant, correlation between %FFM and CRF. More data is being collected to determine if body composition and physical activity levels are strongly associated with CRF in career, structural firefighters. Practical Application: This moderate positive correlation suggests that firefighters begin to understand the effects body composition, specifically FFM has on overall cardiorespiratory fitness. These findings also suggest that fire departments should examine ways to increase and promote PA within their ranks to ensure all members are prepared to meet the demands of the job.

(59) Accuracy of BMI in Classifying Level of Adiposity, Overweight, and Obesity Among Police Officers and Recruits

M. Uftring,1 J. JOYCE,1 F. Kukic,2 A. Cvorovic,2 N. Koropanovski,3 M. Dopsaj,4 and J. Dawes1

1Oklahoma State University;2Abu Dhabi Police;3University of Criminal Investigation and Police Studies; and4University of Belgrade

Obesity is one of the leading public health problems that affects approximately 603.7 million obese adults worldwide. One of the first indicators of weight and health status is body mass index, calculated as body weight (kg) divided by the squared body height (m) (BMI, kg·m−2). Body Mass Index (BMI) is a well-established and standardized estimator of underweight, normal weight, overweight, and obesity, used by the World Health Organization (WHO), but also adopted in occupational health and performance by institutions such as police agencies. Although BMI gives information about the total body volume in ratio to total body size, it does not provide specific information about the source of the volume. This means that 2 persons of the same BMI can possess different relative (%) amounts of fat and lean mass. Therefore, percent of body fat mass (BF%) has also been standardized to define a person's adiposity level, such as essential, average, and obese fat mass classification levels. This is a better measure of obesity and excess body fat mass, as a person that is in a tactical profession and very muscular can be misclassified as overweight or even obese by BMI, but as normal by BF%. Thus, the question arises as to what degree BMI can accurately classify people of different amounts of BF%, especially in tactical athlete professions. Purpose: The purpose of this investigation was to determine the level of agreement between BMI AND BF% in classifying the level of adiposity, overweight, and obesity among police officers and recruits from a Southeast European country. Methods: A retrospective analysis was performed using BMI and body fat analysis data from 485 male police cadets and 579 male police officers. BMI was assessed by taking height and weight measurements and calculating BMI as kg·m−2. BF% was assessed using a multifrequency bioelectric impendence analyzer InBody 720 (Biospace, Korea). Chi-squared was used to determine significant differences in proportions of classifications by BMI and BF%. Results: Based on BMI, 38.3 and 47.9% of recruits and officers were classified as normal weight and overweight, respectively, for a total of 86.2% of subjects, while 86.8% of recruits and officers were classified as having normal fat mass per BF%. There was a 0.6% difference in classification between the 2, which was not significant (p = 0.7829). In terms of obese classification, BMI classified 13.5% of recruits and officers as any class of obese, while BF% classified 13.0% as obese. There was a 0.5% difference in classification of obesity, again which was not significant (p = 0.817). Conclusions: Based on these results, there was no difference in classification of fat mass status by BMI and BF% in officers and recruits, making BMI an accurate measure of obesity in a population of Southeast European police officers and recruits. Practical Application: BMI is a time efficient, inexpensive, and accurate tool for classifying fat mass status and assessing potential health risks within police officer and recruit populations. For officers and recruits who are classified as overweight or obese based on BMI, but appear to have greater muscularity, body composition measurements should be collected as additional measures to confirm health status.

(60) Influence of an Online-Delivered Corrective Exercise Program on the Functional Movement Quality of Male Career Firefighters

D. Cornell,1 K. Ebersole,2 R. Azen,2 K. Zalewski,3 J. Earl-Boehm,2 and C. Alt2

1University of Massachusetts Lowell;2University of Wisconsin-Milwaukee; and3University of Wisconsin-Stevens Point

To meet the essential jobs demands associated with firefighting, firefighters must be capable of performing numerous functional movements. Previous research has demonstrated that a supervised 4-week corrective exercise program is capable of improving the functional movement quality of firefighters. New technologies have recently allowed for the unsupervised delivery of these interventions via online software platforms. However, there is a lack of research examining the efficacy of these unsupervised programs. Purpose: To examine the influence of an online-delivered 4-week corrective exercise program on the functional movement quality of firefighters. Methods: 44 male (28–59 years) career active-duty firefighters (mean ± SD, age: 40.5 ± 7.4 years; height: 179.8 ± 5.3 cm; body mass: 91.1 ± 8.6 kg) were placed into either the control (CON; n = 22) or experimental (CEP; n = 22) groups. Functional movement quality was assessed utilizing the Fusionetics Movement Efficiency (ME) Test pre-, mid-, and post-a 4-week intervention period. The ME Test consists of 7 sub-tests: a 2-leg squat, a 2-leg squat with a heel lift, bilateral 1-leg squats, a push-up test, 4 bilateral shoulder movements, 2 bilateral trunk movements, and 2 bilateral cervical spine movements. The Fusionetics software is then utilized to score each sub-test in a yes/no fashion based on common movement compensations, and an Overall ME Test score ranging from 0 to 100 (worst–best) is calculated. Subjects in the CON group maintained their current exercise programming. Subjects in the CEP group completed corrective exercises via the Fusionetics online software 3–4 d·wk−1. This software utilizes proprietary algorithms to prescribe 10 different corrective exercises (3 self-myofascial release, 3 stretching, 3 strengthening, and 1 dynamic movement) for each day based on movement compensations identified during the ME Test. Adherence was monitored via self-report questionnaires. A 2 × 3 RMANOVA and follow-up pairwise effects were used to identify statistically significant (p ≤ 0.05) changes in Overall ME Test scores between the CON and CEP groups across time. Results: No significant group × time interaction effect was identified on Overall ME Test scores (F2,84 = 1.550, p = 0.218). In addition, no significant differences in Overall ME Test scores were identified within either the CON (F2,42 = 0.449, p = 0.641) or CEP (F2,42 = 2.416, p = 0.102) groups across time (Table 1). Conclusions: Although a 4.4 increase in ME Test scores was observed within the CEP group, significant improvements in firefighter functional movement quality was not observed. Practical Application: Despite the ease of online program delivery, practitioner supervision may be required to elicit significant improvements in functional movement quality within the firefighter population. However, the efficacy of online-delivered corrective exercise interventions at a variety of dosages and frequencies remains unknown.

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(61) Validity of Ultra-Short-Term Measurements of Heart Rate Variability Responses to Training Load in Field Hockey Players: a Longitudinal Analysis

R. Gonzalez-Fimbres,1 G. Hernandez-Cruz,2 and A. Flatt3

1Univeridad Estatal de Sonora;2Universidad Autonoma de Nuevo Leon; and3Georgia Southern University

One-min (i.e., ultra-short-term) measurements of heart rate variability (HRV) responses to internal training load (ITL) have yet to be compared to 5-minute criterion measures throughout a longitudinal training period among youth female athletes. Purpose: To verify the agreement between ultra-short-term and criterion measures when assessing weekly mean of the natural logarithm of the root mean square of the successive differences (LnRMSSDm) and its coefficient of variation (LnRMSSDcv) in response to ITL in youth female field hockey players. Methods: Eleven members (16.8 ± 1.14 years; 157.13 ± 5.15 cm; 55.21 ± 5.20 Kg) from the youth female field hockey Mexican National Team participating in a four-week training camp before the 2018 Youth Olympics in Buenos Aires, Argentina, took part in this study. Daily HRV was measured during the whole four-week camp after waking at 6:00 am. HRV data were collected using a chest-strap transmitter which was connected by Bluetooth to a Smartphone application. After a 1-minute stabilization period, a 5-minute HRV recording was initiated. RMSSD was calculated from the first min and the full 5-minute segment, and later log transformed (Ln). ITL was calculated with a modified heart rate-based training impulse method (TRIMP). Repeated measures ANOVA were used to analyze the effect of time on TRIMP, LnRMSSDm and LnRMSSDcv. For agreement between ultra-short-term and criterion LnRMSSD, paired t-tests and intraclass correlations were performed. Results: Mean and SD for all outcome parameters across time are presented in Table 1. TRIMP in week 4 was lower than all other weeks (p < 0.05). Ultra-short-term LnRMSSDm increased in week 3 relative to week 1 (p < 0.05). Despite a significant model effect, post-hoc analyses revealed no changes across time for LnRMSSD criterion (week 3 vs. week 1, p = 0.06). Pairwise comparisons for each week showed no differences between ultra-short-term and criterion LnRMSSDm (Week 1 p = 0.620, Week 2 p = 0.238, Week 3 p = 0.051, Week 4 p = 0.155) or LnRMSSDcv (Week 1 p = 0.266, Week 2 p = 0.074, Week 3 p = 0.254, Week 4 p = 0.197). Ultra-short-term and criterion measures showed very strong agreement (ICC = 0.979, p < 0.001). Conclusions: Performing ultra-short-term measures is a valid method to assess weekly LnRMSSDm and LnRMSSDcv responses to ITL among youth female athletes throughout a longitudinal training period. Practical Application: Ultra-short-term LnRMSSDm and LnRMSSDcv enhance practicality when assessing weekly responses to ITL among national level youth female field hockey players. Utilizing 1-minute rather than 5-minute recordings reduces compliance demands of athletes, making implementation of HRV monitoring more feasible for coaches.

Table 1 - Mean and SD for LnRMSSD and TRIMP parameters.

(62) Differences in Occupational Performance Among Officers While Wearing Internal vs. External Personal Protective Vests: a Pilot Study

J. Dawes,1 M. Smittle,2 Q. Johnson,1 C. Ward,1 M. Casteel,2 R. Orr,3 and R. Lockie4

1Oklahoma State University;2Stillwater Police Department;3Bond University; and4California State University, Fullerton

Introduction: Law enforcement officers (LEOs) must perform a wide-variety of physically demanding, and often dangerous, tasks as part of their job duties. To preserve their own personal safety, the use of personal protective equipment (PPE) is necessary. However, the type of PPE selected may have a direct impact on physical abilities. For instance, the use of exterior (EXT) vests allow officers to redistribute their occupational loads from a utility belt to the torso, which reduces movement restrictions and thereby potentially improves occupational performance. This requires further investigation in active-duty officers. Purpose: To determine the impact of an internal (INT) versus external (EXT) PPE vest on occupational task performance. Methods: Eleven (Age: 38.81 ± 7.74 years, HT: 179.9 ± 7.86 cm, INT body mass: 110.84 ± 21.83 kg, EXT body mass: 112.76 ± 22.11 kg) male police officers volunteered to participate in this research. Officers performed a physical ability course (PAC) consisting of 4 primary occupational tasks: 30 ft low crawl, 60 ft casualty drag, 30 ft sprint, clearance of three 3 ft barriers, followed by 20 ft another sprint while wearing either an INT or EXT vest and full duty uniform. Officers were allowed 4 trials, and the best test score for each condition was utilized for analysis. Officers then perform a shooting accuracy test for time on a simulator where they were required to shoot a series of 18 pie targets on a large video screen using an infrared training pistol to measure shot accuracy. Officers were then performed a 20-yard sprint after exiting a patrol car. Similarly, the best score for the INT and EXT condition were used for final analysis. Officers performed all measures in a single testing session. The order for each condition (i.e., INT or EXT) was randomized for each trial to reduce the likelihood of any order effects. Paired samples t-tests along with effect size calculations were utilized to determine if significant differences existed between conditions. All statistical analysis were set at a priori p ≤ 0.05. Results: Significant differences (p = 0.01, d = 0.97) were found between conditions on the BM while wearing INT (110.84 ± 21.83 kg) vs. EXT (112.76 ± 22.16 kg) as well as in completion times (p = 0.04, d = −0.71; INT: 41.88 ± 8 seconds vs. EXT: 39.22 ± 7.15 seconds) on the PAC. No significant differences, with small effect sizes were observed between shooting accuracy (p = 0.247, d = 0.32; INT: 86.83 ± 11.18 pts. vs. EXT: 89.67 ± 9.04 pts.) and 20 yard sprint (p = 0.369, d = −0.37; INT: 5.7 ± 0.7 pts. vs. EXT: 5.69 ± 0.72). However, only 9 officers completed the 20-yard sprint test due to various constraints. Conclusion: Despite the additional occupational load, officers performed significantly better on a PAC while wearing an EXT compared to an INT vest. Additionally, though not statistically significant marginal improvements were also found while wearing the EXT vest in the shooting accuracy and while performing the 20-yard sprint. Practical application: Wearing an EXT vest may be more advantageous for officers compared an INT vest form a performance standpoint. It should be noted that this is a small sample and more research is needed to explore the impact of EXT and INT vest from general health and fitness perspective, as well as performance. Future research should also examine the specific physical qualities needed to better tolerate the increases in load observed while wearing the EXT vest.

(63) Cardio-Metabolic and Perceived Demand Comparison of Circuit Training to Fireground Suppression Tasks

B. Loewen, R. Snarr, G. Ryan, and B. Melton

Georgia Southern University

Fireground suppression tasks (FST) require firefighters to perform at high cardio-metabolic intensities. Although firefighters benefit from physical training to prepare for these demands, they often lack the time and equipment to train on-duty. Circuit training (CT) incorporates short rest periods and requires minimal equipment, and may be an appropriate training modality to prepare for the demands of FST. There is currently limited literature comparing CT to FST. Purpose: The purpose was to compare the cardio-metabolic and perceived demands of a task-specific circuit with and without an external load to FST. Methods: Twenty-three career, structural firefighters volunteered to participate. The study was a randomized, repeated measures design and split into 3 separate days (i.e., FST, CT, and CTW). The FST consisted of a single round of 7 commonly performed occupational tasks (e.g., stair climb, hose hoist, hose drag, tool carry, forcible entry, victim search, and victim drag) in full gear (∼22.5 kg). The weighted (CTW: 18.9 kg vest) and unweighted (CT) circuit utilized 7 exercises with similar movement patterns, load, and volume to mimic the FST's (e.g., step-ups, single-arm upright row, forward and reverse sled drag, farmers carry, ball slams, and bear crawl). Average relative heart rate (%HRmax), pre- and post-training blood lactate (Lapre and Lapost), total training time, rating of perceived exertion (RPE) using the OMNI 0–10 scale, and rating of relevance to performing tasks at a fire scene (1 = “not relevant” and 5 = “very relevant”) were recorded during each training session. A repeated measures analysis of variance, with a Bonferroni post-hoc, was conducted to determine differences between the sessions in %HRmax, Lapre, Lapost, and total training time. Friedman's ANOVA was used to assess differences in RPE and rating of relevance ranking. Results: All data is presented in Table 1. For %HRmax, there was a ∼5 and ∼9% lower cardiovascular response between CTW and FST (d = 0.75) and CT and FST (d = 1.12), respectively. Despite a 30–40 seconds longer FST protocol, there were no differences observed in Lapost or RPE between the conditions. The CT session had a lower rating of relevance compared to FST (PSdep = 0.67), however, both the CTW and FST were rated as “very relevant.” All other effect sizes were deemed small and trivial. Conclusions: These findings support previous literature in that CT elicits lower cardiovascular and similar metabolic responses compared to FST, and the addition of the weighted vest did not significantly alter the responses from the CT session. Practical Application: Due to the high-perceived relevance and minimal time commitment, training facilitators may consider utilizing task-specific circuits when training firefighters on-duty. However, future research is needed to determine the longitudinal effect of incorporating circuits at fire departments to improve performance and health.

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(64) The Effects of Military Equipment on Dynamic Stability Using a Hurdle Step Task

J. Thomas,1 A. Long,2 C. McGurk,1 W. Hale,2 G. Sanders,3 and R. Kollock2

1University of Tulsa;2The University of Tulsa; and3Northern Kentucky University

Military personnel are required to carry heavy loads (22 kg) for the purposes of both training and combat. Arguably, these heavy loads have the potential to negatively impact dynamic stability in military personnel. This decrease in dynamic stability has been identified as a risk factor for musculoskeletal injury (MSI), particularly in the lower extremity. Purpose: Therefore, the purpose of this study is to determine the effects of military load on dynamic stability. Methods: Fifteen recreationally active subjects (9 males and 6 females) were recruited for this study (age, 22.2 ± 3.629 years; height, 176.02 ± 8.91 cm; mass, 75.87 ± 14.31 kg). Subjects were asked to complete a hurdle step task under 2 separate conditions: unloaded and loaded. The unloaded condition consisted of shorts, t-shirt, and combat boots. The loaded condition consisted of a combat helmet, improved outer tactical vest, rucksack, and combat boots totaling 22 kg. The hurdle step task required subjects to begin with their dominant foot at a distance of 60% away from a force plate. The dominant limb was defined as the foot the subject would use to kick a soccer ball with maximal force. The non-dominant foot was positioned at a distance of 40% of the subject's height away from the force plate. A hurdle was placed at 20% of the subject's height away from the force plate. When prompted, the subject bounded over the hurdle by pushing off the non-dominant limb and landing onto the force plate with the dominant limb. The subject maintained a quiet stance on their dominant limb for 10 seconds. Three trials were performed for each load condition. The 3 trials were used to calculate average dynamic postural stability index (DPSI) for each of the load conditions, which was the main outcome measure. Data from the force plate were sampled at 1,500 Hz. The first 3 seconds of the ground reaction forces immediately following initial ground contact were used to calculate the DPSI. Initial ground contact was defined as the instant the vertical ground reaction force exceeded 5% body weight. All data was filtered using a low pass Butterworth filter with 20 Hz cutoff frequency. A higher DPSI value represents worse dynamic postural stability. A Wilcoxon signed rank test was used to compare the DPSI between load conditions. Results: Dynamic postural stability index did significantly differ between unloaded (0.433 ± 0.293) and loaded (0.588 ± 0.215) conditions (Z = −3.237, p < 0.001, r = −0.836). Conclusions: The results of this study indicate that military load has a negative impact on dynamic balance. Practical Application: The results suggest a need for dynamic balance training under loaded conditions in populations with minimal load carriage experience such as Army basic training recruits.

(65) The Relationship of Load Carried per Kilogram of Body Mass to Dynamic Stability and Vertical Ground Reaction Force in Firefighters

R. Kollock,1 J. Thomas,2 W. Hale,1 G. Sanders,3 and W. Peveler4

1The University of Tulsa;2University of Tulsa;3Northern Kentucky University; and4Liberty University

Musculoskeletal injuries (MSI) are a common occurrence within fire and rescue. Firefighter specific equipment and gear (EQG) may impact a firefighter's ability to maintain stability and dissipate forces upon landing; thus increasing the risk of MSI. Purpose: The purpose of this study was to examine the relationship of load carried per kilogram of body mass (LPBM) and dynamic postural stability index (DPSI) and normalized vertical ground reaction forces (VGRF) in career firefighters. Methods: Seventeen career firefighters (age, 35.21 ± 8.38 years; height, 173.84 ± 7.14 cm; mass, 89.48 ± 18.31 kg) were recruited for this study. The subjects performed 3 single-leg landing (SLL) trials with and without EQG. The SLL required the subject to drop onto their dominant leg from a 30 cm box placed approximately 10% of their height away from a 40 × 60 cm force plate. Upon landing, the subjects had to stick the landing and remain still for 10 seconds. The subject first performed 3 SLL trials wearing shorts, t-shirt, sneakers and without EQG. Following the without EQG condition, the subjects performed 3 more SLL trials with EQG. The EQG condition included a SCBA, turnout coat, pants, boots, hood, gloves and helmet (combined mass, 24.5 kg). The main outcome measures were average dynamic postural stability index scores (DPSI) and normalized VGRF. The force plate data were sampled at 1,500 Hz. The first 3 seconds of the ground reaction forces immediately following initial ground contact were used to calculate the DPSI. Initial ground contact was defined as the instant the VGRF exceeded 5% body weight. All data was filtered using a low pass Butterworth filter with 20 Hz cutoff frequency. A higher DPSI value represents worse dynamic postural stability. The VGRF from each of the 3 trials was divided by the subject's mass (kg) and averaged. Load carried per kg of body mass was calculated by dividing load carried in kg by subject mass (kg). Separate bivariate correlations were conducted to determine the relationship of LPBM to DPSI and normalized VGRF. Alpha level was set at 0.05. Results: A strong positive correlation was found (r (17) = 0.884, p < 0.001) between LPBM and DPSI. A moderate positive correlation was found (r (17) = 0.685, p = 0.001) between LPBM and normalized VGRF. Conclusions: These results suggest that EQG may have a greater deleterious effect on smaller firefighters' ability to maintain stability and dissipate forces upon landing. Practical Application: Emphasis should focus on inclusion of strength and conditioning programs to increase lean body mass while maintaining cardiorespiratory fitness to help lower the LPBM given up by a firefighter.

(66) Changes in Peak Isometric Strength Following a Test of Aerobic Capacity in Career Firefighters

W. Hale,1 R. Kollock,1 J. Thomas,2 A. Long,1 G. Sanders,3 and W. Peveler4

1The University of Tulsa;2University of Tulsa;3Northern Kentucky University; and4Liberty University

The reliance on muscular strength during fire related duties has necessitated investigation into influential factors. Firefighters are routinely exposed to carrying external loads in excess of 45 kg for long duration. Fire suppression activities that rely on muscular strength include hose line advance, forcible entry, ladder raise, and lifting/lowering objects. These activities may occur with limited recovery and over multiple shifts. A deficit in muscular strength may lead to a decrease in performance and increased risk for musculoskeletal injury following a bout of fatiguing exercise. Purpose: The purpose of this study was to evaluate potential changes in peak isometric strength following a fatiguing test of aerobic capacity in career firefighters. Methods: Following IRB approval and consent, 18 career male firefighters (age 35.21 ± 8.38 years; 173.97 ± 7.33 cm; 90.31 ± 18.66 kg) completed 3 trials of a 5-second isometric mid-thigh pull using a load cell (model LCR; OmegaDyne, Inc., Stamford, CT) before and after a maximal test of aerobic capacity. The peak strength score from the 3 trials was retained for the analysis with a 30-second rest period between trials. The WFI Stepmill test of aerobic capacity was used for test of aerobic capacity. The WFI Stepmill Test is a modified ramp stepping protocol that consists of 20 levels of increased step rate with 12 stages of work. Subjects performed the WFI Stepmill Test until peak V̇o2 was detected. Immediately following the WFI Stepmill Test, the subjects completed the posttest isometric mid-thigh pull. Results: Following confirmation of data normality, a paired samples t-test was performed to compare mean peak strength scores from the pre- and posttest of isometric strength with the level of significance set at 0.05. Results from the paired samples t-test indicated the posttest strength scores (168.10 ± 34.95 kg) were significantly (t (17) = −7.759; p = 0.013) higher than the pretest strength scores (160.30 ± 32.65 kg). Conclusions: Peak isometric strength scores significantly increased following a maximal test of aerobic capacity. The increase in muscular strength may be attributed to post activation potentiation mechanisms such as increased neurological recruitment, cardiac output, and catecholamine activation. Practical Applications: Results from the current study specify increases in peak isometric strength following a fatiguing bout of aerobic exercise. Such findings may support on-duty time for exercise programming specifically with limited recovery between exercise modalities and/or shift change.

(1) Velocity-Specific Neuromuscular Adaptations Following 4-Weeks of Dynamic Constant External Resistance Leg Press Training

O. Salmon and C. Smith

University of Texas at El Paso

Increases in muscle strength within a training period of less than 4-week is generally attributed to neural adaptations and minimal changes within the contractile properties of muscle. Electromyography (EMG) and mechanomyography (MMG) can be used to examine changes in neuromuscular parameters after a short-term dynamic exercise training program. Purpose: Examine changes in neuromuscular parameters from the vastus lateralis (VL) in response to 4-week of Dynamic Constant External Resistance (DCER) leg press training during velocity-controlled movements performed at 60° s−1 and 240° s−1. Methods: 12 recreationally trained (greater than 24- weeks of resistance training, 3-days·wk−1), subjects (age 21.4 ± 3.6 years) participated in this study. Subjects performed maximal isokinetic leg extensions at 60°s−1 and 240°s−1 and one 6-second maximal voluntary isometric contraction (MVIC) on an isokinetic dynamometer for both the right and left leg before and after 4-week of DCER leg press training. Electromyography and MMG root mean square (RMS) and mean power frequency (MPF), were recorded from the VL of each leg during isokinetic and isometric leg extensions. Neuromuscular measurements were calculated from the middle 33% of each maximal isokinetic and isometric leg extension. All neuromuscular parameters were normalized to the pre-test MVIC. The DCER leg press training consisted of 3 sets of 10 repetitions at 70% of their 1-repetition maximum (1-RM) 3-days·wk−1 on a standard leg press. Results: Four separate 2 (visit: pre-test and post-test) × 2 (leg: right and left) × 2 (velocity: 60° and 240°·s−1) repeated measure ANOVAs were performed on neuromuscular parameters, EMG RMS, EMG MPF, MMG RMS and MMG MPF. Results from ANOVA and follow up t-tests indicated no velocity specific changes occurred for any of the neuromuscular parameters except MMG RMS (p > 0.01, ηp2 = 0.78) which indicated that MMG RMS was greater during the 240°·s−1 compared to the 60°·s−1. Muscle activation (EMG RMS) displayed a 36% increase in the right leg (p = 0.03), and no significant change in left leg (p = 0.21). Motor unit action potential conduction velocity (EMG MPF) displayed no significant changes from pre-to post-test (p = 0.97, ηp2 >0.01). Motor unit recruitment (MMG) displayed a 38 and 26% increase at 60° and 240°·s−1, respectively, for the right leg and only a 23% increase at 240°·s−1 for the left leg from pre-to post-test (p = 0.02, ηp2 = 0.41). Motor unit firing rate (MMG MPF) displayed no changes in the right leg at 60° and 240°·s−1 however, the left leg displayed decreases of 23 and 16% at 60° and 240°·s−1, respectively, from pre-to post-test (p = 0.03, ηp2 = 0.38). Conclusions: Four wks of DCER leg press training, did not lead to any velocity-specific improvements in neuromuscular parameters besides MMG RMS when assessed via maximal isokinetic leg extensions at 60 and 240°s−1. The overall neuromuscular response pattern to training suggests that increases in EMG RMS and MMG RMS but decreases in EMG MPF and MMG MPF could be explained by a training-induced muscular recruitment strategy known as the Onion Skin Scheme. Practical Application: Understanding adaptations to dynamic exercise movements and their carryover to neuromuscular changes during a velocity-dependent movement is an important concept for exercise programing and sports application. This can be important considering a 4-week resistance training program is a common mesocycle employed by strength and conditioning coaches.

(2) The Effect of Acute Altitude Exposure on Electromyographic Amplitude and Frequency Responses During Fatiguing Single Leg Extension Exercise

J. Jenkins, O. Salmon, and C. Smith

University of Texas at El Paso

The decreased amounts of available oxygen due to lower pressure at higher altitudes, results in an increased reliance on anaerobic energy production pathways. The increased usage of anaerobic energy sources results in the rapid accumulation of metabolic byproducts, inhibiting neural signal conduction and excitation-contraction coupling. The acute effects of aerobic exercise at high elevations have been well investigated, however, there is a lack of evidence of acute altitude exposure on anaerobic exercise. Purpose: The purpose of this study was to examine the effects of acute altitude exposure on changes in electromyographic (EMG) root mean square (RMS) and EMG mean power frequency (MPF) during fatiguing single leg extension exercise. Methods: To investigate the effects of acute altitude exposure on muscular fatigue, 14 (11 males and 3 females) subjects (mean ± SE; age: 23.2 ± 1.2 years, height: 175.2 ± 1.6 cm, weight: 79.2 ± 6.0 kg) performed one set of fatiguing single leg extension to failure at 70% of their one repetition maximum (1RM) obtained at 3,500 ft, at simulated normobaric elevations of 3,500 ft, 8,000 ft, and 12,500 ft. Electromyography sensors were placed over the belly of the right vastus lateralis and sampled at 2,000 Hz. The EMG RMS and EMG MPF values were calculated from the middle 33% of the concentric phase of each repetition. Repetitions were selected as 10, 50 and 100% of total repetitions completed, if percent failure was between repetitions, the repetitions immediately following was selected. Results: The Altitude × Repetition repeated measures ANOVA was not significant for EMG RMS (p = 0.495; ηp2 = 0.052) or EMG MPF (p = 0.176; ηp2 = 0.119). In addition, there was no main effects for altitude (EMG RMS: p = 0.417, ηp2 = 0.055; EMG MPF: p = 0.130, ηp2 = 0.161). There was a main effect for EMG RMS across repetitions (p > 0.001; ηp2 = 0.583) which indicated that 10% < 50% (p = 0.002) >100% (p > 0.001). There was also a main effect for EMG MPF across repetitions (p > 0.001; ηp2 = 0.712) which indicated that 10% > 50% (p = 0.001) > 100% (p = 0.039), and 10% > 100% (p > 0.001). There was no significant one-way ANOVA for number of repetitions between each altitude condition (p = 0.972; ηp2 = 0.002). Conclusions: Acute altitude exposure had no effect on changes in EMG RMS and EMG MPF during fatiguing single leg extension exercise at 70% 1RM. There was also no difference in the number of repetitions achieved between each altitude condition. Practical Application: Exercising at higher elevation causes similar time course of changes in neuromuscular response during the process of fatigue as well as the muscular endurance of fatigue at normal altitude. This could be useful for Strength and Conditioning coaches to consider when designing training programs at higher elevations.

(3) Difference in Sagittal Plane Kinematics Utilizing 3 Hand Positions in the Front Squat

J. Taylor,1 M. Sommer,1 M. Morales,1 L. Maldonado,1 W. Amonette,2 J. De Witt,2 and J. Dean1

1University of Houston-Clear Lake; and2University of Houston—Clear Lake

Purpose: To characterize the biomechanics of front squats using front-rack (FR), cross-grip (CG), and strap-assisted (SA) hand positions. Methods: Eight experienced weightlifters volunteered (6 M:2F, 24.50 ± 3.00 years, 78.20 ± 12.30 kg,