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Medicine & Science in Sports & Exercise:
doi: 10.1249/01.mss.0000433620.89544.ee
Abstract

A-45 Free Communication/Poster - Squat/Jump/Landing Mechanics

Free Access

May 29, 2013, 7:30 AM - 12:30 PM

Room: Hall C

331 Board #184 May 29, 9:30 AM - 11:00 AM

Kinematics of Countermovement Vertical Jumps in Overweight and Normal-Weight Children

Jeffrey C. Cowley1, Kelly R. Laurson2, Steven T. McCaw, FACSM2, Michael R. Torry2, Luis M. Justiniano2. 1University of Michigan, Ann Arbor, MI. 2Illinois State University, Normal, IL.

(No relationships reported)

Introduction: Prevalence of conditions associated with inactivity, including overweight, is increasing in children. Little is understood about the effects of overweight on children’s movement skills.

PURPOSE: To investigate the effects of overweight on countermovement vertical jumps in children.

METHODS: Sagittal plane kinematics of the hip, knee, and ankle during maximum-height countermovement vertical jumps were obtained from 11 overweight (age=7.0 y, SD=1.5; BMI=15.2, SD=1.4) and 28 normal-weight (age=7.1 y, SD=1.6; BMI=19.5, SD=2.0) children using a 3D motion capture system. An independent t-test was used to compare kinematic data between groups at each joint (α=.05).

RESULTS: The overweight children exhibited less flexion at the hip (p=0.045) and knee (p=0.023)but not the ankle (p=0.394) at the end of the countermovement and utilized a smaller ROM during the jump phase at the hip (p=0.024) but not the knee (p=0.055) or ankle (p=0.303). Normal-weight children jumped 1.5 cm higher than overweight children (p=0.113). No significant differences were observed in peak joint angular velocities.

CONCLUSIONS: Overweight and obese children did not achieve as much hip and knee flexion as their peers during the jump’s countermovement, likely limiting the range of motion over which the hip and knee extensors contributed energy to the jump.

332 Board #185 May 29, 9:30 AM - 11:00 AM

Validation and Reliability of a Single Leg Squat Test for Use with Adolescent Runners

Cristine Agresta1, Chris Church2, Angelica Montes2, John Henley2, Tim Duer2, Nancy Lennon2, Richard Kruse2, Kathleen O’Brien2, Freeman Miller2. 1Temple University, Philadelphia, PA. 2A.I. DuPont Hospital for Children/Nemour’s Children’s Clinic, Wilmington, DE.

(No relationships reported)

The single leg squat test (SLS) is a frequently used clinical tool to evaluate functional movement patterns and help identify runners at risk for injury. SLS assessment is often done visually without the use of technology, like video, or instrumented devices. The knee frontal plane projection angle (FPPA), a 2D knee angle measure, appears to capture some key variables associated with knee pain. FPPA angle can be assessed by visually inspecting the relative positions of the knee and foot, or knee-to-foot (KTF) distance, during squatting.

PURPOSE: To determine the reliability and validity of the SLS for use with adolescent runners.

METHODS: Thirty healthy children ranging from 9-20 years old (16 F, mean age: 13.4 ±3.5) performed a series of SLS on both extremities. Two investigators independently rated 60 SLS using a modified lateral step down scoring system. The investigators then re-scored 20 SLS to establish intrarater reliability. The examiners scored the test based on 5 criteria: arm strategy, trunk movement, pelvis plane, knee position, and maintenance of steady unilateral stance. Kinematic data for running (9 mph) and the series of SLS was collected using a 12-camera motion analysis system. Concurrent validity was determined by comparing points awarded for knee position on the SLS to coronal plane KTF distance calculated from 3D kinematic data from 10 right and left squats from two subjects. Predictive validity was determined by comparing KTF distance during stance phase of running to points awarded for knee position on the SLS.

RESULTS: Intrarater (r=0.86, p < 0.001) and interrater reliability (r=0.75, p < 0.001) were high. Concurrent validity for knee position scoring was high (r=-0.92, p < 0.001), where a negative association indicates poorer form (i.e. higher points) and increasing KTF distance. SLS knee position score and KTF distance during stance phase in running were not as strongly correlated as squat data (r=-0.31, p < 0.01), but showed appropriate directionality. 3D squat KTF distance was moderately correlated to KTF distance during stance phase in running (r=0.44, p < 0.01).

CONCLUSIONS: The SLS appears to be a valid and reliable test for assessing lower extremity stability without the need for external tools or instrumentation, and may be useful in detecting runners at risk for knee injuries.

333 Board #186 May 29, 9:30 AM - 11:00 AM

Unique Activation Patterns of The Vastus Intermedius in The Quadriceps Femoris Muscles during Squat Movement

Makoto Kawai1, Keigo Taniguchi1, Akira Saito2, Nobuhiro Aoki1, Hiroshi Akima2, Masaki Katayose1. 1Sapporo Medical University, Sapporo, Japan. 2Nagoya University, Nagoya, Japan. (Sponsor: Dr. Katsumi ASANO, FACSM)

(No relationships reported)

The squatting exercise is one of essential weight-bearing exercises used in rehabilitation programs. During squatting, the quadriceps femoris (QF) synergists simultaneously act together to control of the movement. Unfortunately, the activation patterns of the vastus intermedius (VI) located in the deep region of the QF have not been investigated during squat movement due to technical difficulty to record surface EMG. However, by using a recent innovative technique, it is possible to record activity of the VI using surface electromyography (EMG) during dynamic knee extensions (Akima & Saito, in press).

PURPOSE: The purpose of this study is to determine the neuromuscular activation patterns of the QF muscle group including VI during squat movement.

METHODS: For 14 healthy men (22.0 ± 1.8 years), surface EMG was recorded at VI, vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) during the repetitive squat movements. The squat movement started upright posture. This movement consisted of eccentric (ECC) phase of 3-s, isometric (ISO) phase of 2-s at the bottom, and concentric (CON) phase of 3-s with knee joint angle between 180° to 90° (180° = full extension). The root mean square (RMS) of the EMG signals during three phases was calculated for knee joint angles ranging from 165° to 90°. Each ECC and CON phase was further divided into three subcategories (165° to 140°, 140° to 115° and 115° to 90°) with every 25° depending on the knee joint angles. The RMS during squat was normalized by that of 165° to 140° during the ECC phase (ECC 165-140) for all muscles.

RESULTS: During the squat movement, a significant muscle-by-angle interaction in normalized RMS was found (P < 0.05). The normalized RMS of VI was significantly higher than that of the VL and VM at all subcategories during ECC phase and ISO phase (P < 0.05). During CON phase, the normalized RMS of VI was also significantly higher than that of VL and VM at CON 115-140 and CON 115-90 (P < 0.05).

CONCLUSION: These results suggest that the VI plays an important role in the flexed knee position during squat movement. This uncovered finding may help establishment of future effective therapeutic programs for dysfunction of QF related knee joint disorders.

334 Board #187 May 29, 9:30 AM - 11:00 AM

2d Knee and 3d Motion Relationships of the Hip and Knee during Bilateral Drop Landing

Haley Bawek1, Thomas W. Kernozek, FACSM1, John D. Willson2, Robert Ragan1. 1University of Wisconsin-La Crosse, La Crosse, WI. 2East Carolina University, Greenville, NC.

(No relationships reported)

Knee joint kinematics during bilateral landings are often clinically evaluated using two dimensional (2D) motion analysis to assess frontal plane knee motion and risk for anterior cruciate ligament injury. However, it is unknown how 2D frontal plane projection angles of the knee (2D FPPA) relate to three dimensional (3D) hip and knee motions during landing.

PURPOSE: To determine the relationships between 2D knee and 3D knee and hip kinematics during bilateral landings.

METHODS: Thirty college-aged females (19-24 yrs, 65.8 + 12.4 kg) performed a series of five 40 cm bilateral drop landings. An eight camera motion analysis system sampling at 240 Hz and integrated force platforms sampling at 2400 Hz under each leg were used to obtain 3D marker data for the pelvis, thigh, and shank segments during ground contact when the vertical ground reaction force was greater than 20 N. Marker data were used to determine the 2D knee FPPA and 3D kinematics of the hip and knee. Pearson product moment correlations were performed between 2D and 3D angles at contact and for joint excursion from the first 50% of the contact phase. A multiple linear regression was used to predict 2D knee FPPA at contact and 2D knee FPPA excursion from 3D knee and hip kinematic variables.

RESULTS: 2D FPPA at contact was associated with 3D knee frontal plane angle at contact (r=0.82, r2=0.67). However, 2D knee FPPA excursion and 3D knee and hip kinematic excursions were more weakly associated (r<0.5). 2D FPPA at contact were predicted by 3D peak knee abduction and peak hip internal rotation angle (r=0.86, r2=0.74). 2D FPPA excursion were predicted by 3D hip adduction excursion and knee abduction excursion (r=0.66, r2=0.44).

CONCLUSION: Knee frontal plane angles at contact are associated in 2D and 3D kinematic measures. 2D FPPA excursion is associated with 3D knee abduction and hip adduction in bilateral drop landing of female participants.

335 Board #188 May 29, 9:30 AM - 11:00 AM

Trunk and Hip Neuromuscular Training Protocol Effects on Female Athletes’ Landing Mechanics

Charley J. Young, Pamela J. Hansen, Donna J. Terbizan, FACSM, Bryan Christensen, Elizabeth Boldgett Salafia. North Dakota State University, Fargo, ND.

(No relationships reported)

Noncontact ACL injuries have an incidence rate three to eight times higher in female high school athletes compared to their male counterparts. Poor biomechanics during dynamic activity resulting from neuromuscular imbalances may contribute to the cause. Landing is a dynamic activity and considered one of the leading causes of noncontact ACL injuries.

PURPOSE: To determine if a trunk and hip neuromuscular training program for female high school athletes facilitates neuromuscular changes during landing mechanics.

METHODS: Eleven healthy female high school volleyball, soccer, or hockey athletes (14.91±1.04 yrs; 64.24±5.40 kg; 170.87±6.82 cm) volunteered for the study. The Landing Error Scoring System (LESS) assessed by a single investigator evaluated the drop box jump, pre, mid, and post, for any changes in the landing mechanics due to neuromuscular changes. The eight week neuromuscular training protocol consists of 13 exercises with each exercise having five individual phases. The exercises consisted of core stability, plyometrics, propreoception, and strengthening exercises. At the end of the study, participants filled out a survey regarding their perceptions of neuromuscular changes and their landing mechanics. A repeated measures ANOVA was conducted to determine whether the neuromuscular protocol affected the participants’ landing mechanics significantly (p<0.05). Chi square was used to determine participant’s perception (p<0.05).

RESULTS: The decrease in LESS scores seen after the neuromuscular protocol indicates the participant’s landing mechanics improved significantly (p=0.001). Regarding the participant’s perceptions of the training program, participants felt their landing mechanics improved (p=0.035), the hip and trunk neuromuscular training program made them stronger (p=0.003), and that the training program helped them become more aware of their body (p=0.035).

CONCLUSION: An eight week hip and trunk neuromuscular program improved landing mechanics in these high school female athletes. The participants also perceived this improvement. This type of training may help decrease noncontact ACL injuries in this population of young athletes.

336 Board #189 May 29, 9:30 AM - 11:00 AM

Lean Mass Asymmetry Influences Force and Power Asymmetry During Jumping in Collegiate Athletes

David R. Bell, Jennifer Sanfilippo, Shelton Johnson, Jessie Libber, Diane Krueger, Neil Binkley, Bryan C. Heiderscheit. University of Wisconsin-Madison, Madison, WI. (Sponsor: Joseph Weir, FACSM)

(No relationships reported)

Jumping is a combination of power, strength, and coordination and provides an estimate of muscle function. Deficiencies in lower extremity lean mass may reduce the ability to produce force and power during jumping, thus negatively influencing performance. Lean mass asymmetry may provide useful insight into force and power asymmetry during jumping and begin to clarify morphological versus neuromuscular contributions to performance.

PURPOSE: The purpose of this investigation was to examine how asymmetry in lower extremity lean mass influenced force and power asymmetry during jumping.

METHODS: 167 Division I athletes were tested after their competitive season in the spring of 2012. Peak force (kN) and power (kW) were assessed from each limb using bilateral force plates during a countermovement jump. Lean mass (g) of the pelvis, thigh, and shank was assessed via Dual-Energy X-Ray Absorptiometry. A limb symmetry index (LSI) was established using the following equation for each variable of interest: LSI = (right limb - left limb) / 0.5 (right limb + left limb) X 100. In this equation, zero indicates symmetry between limbs; a positive (+) value indicates that the right limb is greater; and a negative (-) value indicates the left limb is greater. Forward stepwise regressions were performed to determine the influence of lean mass LSI on force and power LSI. All statistical analyses were performed in R Statistical Software, with significance set a priori at P < 0.05.

RESULTS: Lean mass LSI of the thigh (2.7 ± 6.7%) and shank (2.6 ± 3.3%) entered into the model and explained 20% of the variance in peak force LSI (1.2 ± 7.4%, R2 = 0.20, P < 0.001). For peak power LSI (0.4 ± 5.8%), lean mass LSI of the pelvis (0.2 ± 5.6%), thigh and shank all contributed to the model, explaining 25% of the variance (R2 = 0.25, P < 0.001).

CONCLUSIONS: While lean mass asymmetry appears to be a significant contributing factor in force and power asymmetry, there still remains a large percentage of the variance unexplained. Other factors not assessed in this study most likely account for the remaining variance including neuromuscular control, muscular strength, and joint coordination. Future research should attempt to examine morphological and functional asymmetry and their influence on injury rates.

Supported by the UW Sports Medicine Research Fund.

337 Board #190 May 29, 9:30 AM - 11:00 AM

Frontal Plane Projection Angle Relationship with Three-dimensional Hip and Knee Kinematics during Jump Landing

Clare E. Milner, FACSM1, Jeremiah J. Tate2, Richard A. Brindle1. 1University of Tennessee, Knoxville, TN. 2University of Tennessee, Chattanooga, TN.

(No relationships reported)

Associations between knee frontal plane projection angle (FPPA) and three-dimensional hip and knee kinematics have been reported in the literature. Tasks evaluated previously include drop vertical jump, single leg squat and step down. Countermovement jump (CMJ) is a controlled landing task that has not been evaluated.

PURPOSE: To determine whether frontal and transverse plane hip and knee angles are correlated with FPPA at peak knee flexion during CMJ landing.

METHODS: As part of a larger study, data from 26 female recreational athletes were collected. Marker trajectories were collected using a 7 camera motion capture system sampling at 240 Hz. Participants completed 5 trials of CMJ, with a target set at 80% of maximum jump height. Data were analyzed using Pearson product moment correlations.

RESULTS: Table 1: Variables of interest at peak knee flexion during CMJ and correlation with FPPA Positive angles indicate adduction and internal rotation.

Positive angles indicate adduction and internal rotation.

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Frontal plane hip and knee angle had large, significant correlations with FPPA. Hip rotation had a moderate, significant correlation with FPPA. DISCUSSION: Previous studies with controlled tasks have shown small to moderate relationships between FPPA and frontal plane hip or knee angle. We found strong correlations between these variables and FPPA in the CMJ. Previous studies indicate that FPPA calculated from motion capture data is similar to FPPA measured from video data. Therefore, these results suggest that FPPA may be used as an indicator of frontal plane hip and knee joint angle at peak knee flexion during a CMJ landing.

CONCLUSION: Measuring FPPA in the CMJ task may provide a better indication of hip and knee frontal plane angle compared to tasks reported previously.

338 Board #191 May 29, 9:30 AM - 11:00 AM

2d And 3d Relationships Between Knee And Hip Kinematics: Single Leg Drop Landings

Bryan P. Sorensen1, Thomas W. Kernozek, FACSM1, John D. Willson2, Robert Ragan1. 1University of Wisconsin-La Crosse, La Crosse, WI. 2East Carolina University, Greenville, NC.

(No relationships reported)

Frontal plane knee motion during landing has been related to ACL injury. Two dimensional (2D) analysis of hip and knee kinematics is often used in screening for an athlete’s injury risk. However, the relationship between 2D frontal plane hip and knee motion during landing and three dimensional (3D) hip and knee joint kinematics is unclear.

PURPOSE: Examine the relationship between 2D and 3D hip and knee kinematics during single leg landing.

METHODS: Thirty one females (19-25 yrs, 66.4+12.5 kg) performed five 40 cm drop landings onto their right leg while being measured with 3D motion system at 240 Hz. Initial contact (IC) was determined from force platform data. 2D frontal plane projection angles (FPPA) for the hip and knee were calculated using 3D data from the bilateral ASIS markers and endpoints of the distal femur and distal shank. 3D joint kinematics were measured from either marker arrays or single markers placed on the pelvis, thighs, shanks and feet using standard procedures. Pearson product moment correlations were performed between hip and knee FPPA and 3D hip and knee angles at IC and maximal joint excursion in all planes. Multiple regressions were used to predict knee and hip FPPA from 3D hip and knee angles.

RESULTS: At IC, 2D knee FPPA was associated with 3D knee frontal plane angle (r=.849, r2 =.721) and 2D hip FPPA was associated with 3D hip frontal plane angle (r=.723, r2 =.521). 2D hip FPPA peak adduction (ADD) excursion and 3D hip maximum (max) ADD excursion were related (r=.863, r2= .745) and 2D hip FPPA peak abduction (ABD) excursion and 3D hip max ABD excursion were related (r=.797, r2=.635). 2D knee FPPA at IC was predicted by knee flexion and ABD (r2=.759). 2D hip FPPA at IC was predicted by 3D hip flexion and ADD at IC (r2=.599). Max 2D hip FPPA ADD excursion was predicted by 3D hip max ADD excursion (r2=.698) and max 2D knee FPPA ABD excursion was predicted by max 3D knee ABD and external rotation (r2= .686).

CONCLUSION: 2D knee and hip FPPA are strongly correlated with frontal plane 3D kinematics at IC. 2D FPPA of the hip and knee joint excursions are influenced by motions in the sagittal and transverse plane, respectively, which have not previously been clearly described during single leg drop landing. These findings have the potential to influence ACL injury screening protocols for participants in landing sports.

339 Board #192 May 29, 9:30 AM - 11:00 AM

Intensity Rankings of Plyometric Exercises using Joint Power Absorption

Kathryn G. Van Lieshout1, Owen R.W. Dennis1, Joy G. Anderson2, Kevin B. Shelburne1, Bradley S. Davidson1. 1University of Denver, Denver, CO. 2University of Colorado, Aurora, CO.

(No relationships reported)

Rehabilitation often incorporates plyometric exercises to improve dynamic stability of the injured joint. Current recommendation is to gradually “increase plyometric intensity”; however “intensity” is subjectively gauged by the therapist. Few unbiased biomechanical assessments of intensity exist and largely focus on maximum efforts.

PURPOSE: 1) To quantify and rank intensity of rehabilitation level plyometric exercises using total power absorption (TPA) and 2) evaluate contribution of joint-specific power absorption (JPA). We hypothesize that TPA will rank intensity according to drop height, and JPA will provide more applicable rankings.

METHODS: Six collegiate athletes performed submaximal plyometric exercises in a single test session: vertical jump (VJ), forward jump (FJ), backward jump (BJ), box drop (BXD), box jump-up (BXJ), tuck jump (TJ), and depth jump (DJ). Three-dimensional kinematics and force platform data were collected and joint kinetics were generated using Visual 3D. Peak power absorption normalized to body mass was calculated at the ankle, knee, and hip, and averaged across repetitions. These JPA data were pooled across participants and summed to obtain TPA. Exercises were ranked by TPA.

RESULTS: Relative to baseline VJ, TPA was lower in 4 exercises and higher in 2 exercises (Fig 1). Distribution of JPA did not directly correspond with increase in TPA.

CONCLUSION: As expected, TPA related to drop height and was a reliable objective metric of overall intensity. However, disparities between TPA and JPA indicate that joint-level demand should be ranked independently of overall demand. This suggests that a joint-specific ranking may be helpful to objectively guide plyometric rehabilitation in injured athletes.

340 Board #193 May 29, 9:30 AM - 11:00 AM

An Investigation Of The Relationship Between The Symmetry Index Of Strength And Drop-landings

Lemuel Brown1, Jeni McNeal2, Jessica Savage2, Kinyanjui Kimuhu2, Tyrone Washington1, Alan Coelho2. 1University of Arkansas, Fayetteville, AR. 2Eastern Washington University, Cheney, WA. (Sponsor: Stavros Kavouras, FACSM)

(No relationships reported)

Jumping is an important lower extremity (LE) skill used by any individual that takes part in sports that involve explosive movement. Performing this skill successfully requires a person to land properly and without injury. More recent evidence has suggested that seemingly symmetrical bilateral activities like jumps and landings may in fact not be symmetrical. Furthermore, these asymmetrical differences may affect performance in daily activities, work, and sport. Studies have found that strength asymmetries in the lower extremities also exist and may be related to injury in the lower limbs.

PURPOSE: : to investigate whether there is a relationship between asymmetry in LE strength and vertical ground reaction forces (VGRFs) in drop-landings (DL) in healthy individuals.

METHODS: Sixteen subjects (mean ± SD: age = 23.5 ± 3.4 yr; height = 1.77 ± 10.3 m; weight = 86.8 ± 20.1 kg) performed 3 isometric leg press (ILP) tests with each leg. Subjects also participated in 3 drop-landings from 30 cm on two force plates after hanging on two gymnastic rings. We obtained the symmetry index of peak force and VGRFs relative to body weight for the dominant leg (SIDI, SIDL) and stronger leg (SISI, SISL).

RESULTS: All values indicated a significant difference in the symmetry index of ILP and VGRFs in DL for the dominant and stronger leg (SIKI t(14) = 3.390, p = .004; SIDI t(14) = 2.959, p = .010; SIDL t(14) = 6.619, p < .001; SISL t(14) = 6.472, p < .001). The Pearson correlation demonstrated no significant relationship between strength and landing asymmetry for both dominant and stronger leg: SIDI and SIDL (r = .133, p = .638); SISI and SISL (r = .165, p = .558).

CONCLUSIONS: Asymmetries do exist in healthy populations however there is no relationship with DL VGRFs and maximal strength in ILP.

341 Board #194 May 29, 9:30 AM - 11:00 AM

Immediate Effects of Real-time and Traditional Feedback on Knee and Hip Biomechanics During Landing

Hayley Ericksen. University of Toledo, Toledo, OH.

(No relationships reported)

Females have demonstrated altered biomechanics when landing from a jump, including increased knee abduction and decreased knee flexion angles, which may increase risk of non-contact ACL injury. Feedback has demonstrated the ability to alter biomechanics during landing; however, delivery of feedback has yet to be optimized.

PURPOSE: Determine the effect of a single session of real-time feedback (RTF) on knee and hip kinetics and kinematics compared to traditional feedback (TF), jumping only and a true control group.

METHODS: Twelve RTF (20.33±1.5 yrs; 164.5±5.5 cm 65.7±8.2 kg), 12 TF (20.58 yrs; 167 cm; 61.44 kg) 11 jumping (20.54 yrs; 163.42 cm; 63.89 kg), and 8 control (21.13 yrs; 160 cm; 60.39 kg) subjects performed 3 jump landings off a 30cm box pre- and post-intervention, consisting of 18 jump landings (RTF, TF, and jumping) or no intervention (control). RTF and TF received verbal and visual cues of correct landing technique from a single clinician after each set of 6 jumps. RTF subjects were provided real-time, visualization of their frontal plane knee angle and were instructed to align this knee angle with a reference line during landing. Jumping subjects performed 18 jump landings with no feedback. Peak knee and hip sagittal and frontal plane biomechanics were determined during the first 25% of stance pre- and post-intervention using standard inverse dynamics analysis. Data were analyzed using 2x4 repeated measures ANOVAs and Tukey multiple comparisons.

RESULTS: Subjects in the TF group (pre: 98.8°±9.5; post: 107.6°±13.2) increased their knee flexion angles compared to jumping subjects (pre: 84.2°±21.1; post: 82.9°±20.7, P=0.01). TF did not influence hip sagittal plane or knee or hip frontal plane biomechanics (P>0.05). RTF did not influence knee or hip frontal or sagittal plane biomechanics (P>0.05).

CONCLUSION: The TF group increased their knee flexion angle compared to the jumping group. There may be no immediate benefit of adding RTF in altering lower limb biomechanics. Future research should look to screen patients to identify who may best respond to various modes of feedback. Additionally, multiple sessions may be needed to realize the full benefit of feedback.

342 Board #195 May 29, 9:30 AM - 11:00 AM

Lower Extremity Energy Absorption During Double-Leg Jump Landings is Not Influenced by Limb Dominance

Marc F. Norcross1, Christine D. Pollard2, Sam T. Johnson1, Mark A. Hoffman, FACSM1. 1Oregon State University, Corvallis, OR. 2Oregon State University- Cascades, Bend, OR.

(No relationships reported)

Greater sagittal and frontal plane energy absorption (EA) in the 100 ms following initial contact (IC) during double-leg jump landings (DLJLs) are indicative of biomechanical landing profiles that are associated with increased ACL injury risk. However, these findings have been restricted to the dominant limb; and it is unknown if individuals who demonstrate elevated EA in one limb, also exhibit this high-risk profile on the opposite limb.

PURPOSE: To compare total and individual joint EA between dominant and non-dominant limbs during DLJLs. We hypothesized that sagittal and frontal plane EA magnitudes would not differ between limbs.

METHODS: Lower extremity kinematics and kinetics were measured bilaterally in 21 healthy subjects (12M, 9F) during DLJLs from a 30cm box. Hip, knee, and ankle joint angular velocities were multiplied by net joint moments obtained using inverse dynamics to produce sagittal and frontal plane joint power curves. The negative portions of each joint power curve were then integrated during the 100 ms following IC to calculate joint EAs. Total EA was determined by summing hip, knee, and ankle EA. EA was compared between dominant (D) and non-dominant (ND) limbs using paired samples t-tests; while the relationships between total D and ND EA in the sagittal and frontal planes, respectively, were assessed via Pearson correlation coefficients (α = 0.05).

RESULTS: Sagittal plane total (D: 126.93 vs. ND: 126.47 J), knee (D: 76.90 vs. ND: 79.13 J), and ankle (D: 24.65 vs. ND: 25.11 J) EA; and frontal plane total (D: 3.15 vs. ND: 2.96 J), hip (D: 1.67 vs. ND: 1.55 J), knee (D: 0.98 vs. ND: 0.99 J), and ankle (D: 0.49 vs. ND: 0.42 J) EA did not differ between limbs (p > 0.05). Sagittal plane hip EA was greater in the dominant limb (D: 25.38 vs. ND: 22.23 J, p = 0.008). Total EA in the sagittal (r = .610, p = 0.003) and frontal (r = .604, p = 0.004) planes was significantly correlated between limbs.

CONCLUSION: The similarity of total and individual joint EA magnitudes between limbs indicates that participants generally utilized a balanced EA strategy. While sagittal plane hip EA was greater in the dominant limb, it is likely that the magnitude of this difference is not clinically relevant. These results suggest that healthy individuals utilizing higher risk landing strategies during DLJLs do so bilaterally.

343 Board #196 May 29, 9:30 AM - 11:00 AM

Influence of Whole Body Vibration on Knee Mechanics during a Drop Jump Maneuver

D Clark Dickin, Ryan Hubble, Paul Nagelkirk, He Wang. Ball State University, Muncie, IN.

(No relationships reported)

Whole body vibration (WBV) is a training modality that involves an individual positioning themselves on a platform that provides vibrations at set or varied frequencies and amplitudes to the body. Research has shown changes in force production following WBV. A common method used to assess this has been through jump performance. Considerable evidence has illustrated its effectiveness at improving jump height, however the ability to absorb the eccentric forces when landing from a jump and potentially preparing to initiate another movement are unknown. Landing mechanics have previously been linked to injury risk.

PURPOSE: The purpose of the study was to (a) identify the effects of WBV on ground reaction forces (GRF), loading rates, valgus knee angles, frontal plane knee moment and jump height, and (b) compare these responses between men and women.

METHODS: Nine men and ten women completed the study. Ten, 1-minute vibrations (2mm, individualized frequency) were administered. Subjects completed drop jumps from a 0.6m height prior to, immediately after and at 10 and 20 minutes post-vibration. All dependent measures were obtained using an AMTI force platform and 12-Vicon motion capture system. Data were analyzed using RM-ANOVA with significance set at p≤0.05.

RESULTS: No significant changes in GRF or loading rate were found across time or gender. A significant main effect was found for valgus knee angle across time (p=0.011). Follow-up pairwise contrasts illustrated an increase at all three times post vibration (-9.18, -10.03, -10.15, -10.36, for pre, post, 10min & 20min post, respectively). Women had a significantly greater overall knee moment than men (0.32 vs. 0.79 Nm/kg) (p=0.038), and men jumped higher than female participants (0.41 vs. 0.29m) (p<0.001).

CONCLUSIONS: Findings from this study indicated that, compared to baseline, subjects landed with significantly greater knee valgus angles following WBV. Although females have been shown to have a higher degree of valgus knee angle during landings it is important to note that we observed no effect of gender. Since it has been demonstrated that a knee in a valgus position while landing increases the potential risk for anterior cruciate ligament injury, caution should be taken when combining WBV and jump training protocols.

344 Board #197 May 29, 9:30 AM - 11:00 AM

Relationships Between Quantitative And Qualitative Measures Of Jumping In Typically Developed Preschoolers

Hsiu-Chen Lin, Ching-Ling Wang, Shih-Heng Sun. China Medical University, Taichung, Taiwan.

(No relationships reported)

Preschool period is critical in developing fundamental motor skills, such as jumping. Relations between quantitative and qualitative measures in jumping were seldom found.

PURPOSE: To determine the correlations between quantitative measures of standing long jump (SLJ) and vertical jump (VJ) and qualitative scores of gross motor development in preschoolers.

METHODS: A video-based motion capture system was used to obtain the quantitative measures including takeoff angle (TOA), takeoff velocity (TOV), trunk inclination angle (TIA), trunk extension range (TER), slopes of angle-angle plots in lower limbs (hip-knee plot (SHK), hip-ankle plot (SHA), and knee-ankle plot (SKA)) during pre-takeoff and jump performance (distance or height). Preschooler Gross Motor Quality scale (PGMQ) was used to obtain the qualitative scores of horizontal jumping (L3 score) and gross motor development (PGMQ score). Correlation analysis between variables used Spearman’s rho, and statistical significance was set at 0.05.

RESULTS: Many quantitative measures in both SLJ and VJ were correlated to the PGMQ score, indicating these parameters could represent certain features of motor development. TIA in SLJ and VJ was respectively high and moderate correlated to the L3 score. TOA and jump performance were correlated to the L3 score only in SLJ, but TER only in VJ, suggesting different features and strategies between SLJ and VJ.

CONCLUSION: Selective quantitative measures in SLJ and VJ were related to the qualitative scores in preschoolers. Trunk movement and slope of hip-ankle plot during pre-takeoff were important parameters correlated to motor development.

Supported by NSC Grant (NSC100-2628-H-039-005 -MY2).

Table 1
Table 1
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345 Board #198 May 29, 9:30 AM - 11:00 AM

Gender Differences In Single-leg Squat Kinematics Of Healthy Young Adults

Benjamin K. Weeks, Steven L. Watson, Sean A. Horan. Griffith University, Gold Coast, Queensland, Australia. (Sponsor: Belinda R. Beck, FACSM)

(No relationships reported)

There is some evidence to suggest that certain lower limb movement patterns during functional activities increase the risk of lower limb injuries, such as non-contact anterior cruciate ligament (ACL) tears. Further, the prevalence of such risky movement patterns appears to be greater amongst women than it is for men; an observation that is commensurate with ACL injury rates. Despite widespread use of the single-leg squat (SLS) test in musculoskeletal screening, a comprehensive gender comparison of trunk, pelvis, and lower limb 3D kinematics is yet to be described.

PURPOSE: To determine gender differences in SLS kinematics in healthy young adults.

METHODS: We recruited 60 healthy men and women between the ages of 20 and 40 years. Participants had 32 retroreflective markers attached to their trunk, pelvis, and lower limbs before performing three SLSs on an AMTI force plate while 3D kinematic data was simultaneously collected with a ten-camera VICON motion analysis system (Oxford Metrics, UK). Squat depth was standardised by asking participants to achieve 75 degrees of knee flexion using real time kinematic feedback. One-way ANOVA was used to make gender comparisons of kinematic parameters.

RESULTS: 30 men (25.6 ±4.8 years) and 30 women (25.1 ±3.8 years) volunteered to participate. Men were taller (1.78 ±0.08 m vs. 1.68 ±0.06 m) and heavier (77.3 ±12.0 kg vs. 59.7 ±8.2 kg) than women. Angles for peak hip external rotation (-13.4 ±5.4 deg vs. -10.0 ±4.4 deg, p=0.02), peak hip internal rotation (-2.7 ±5.3 deg vs. 3.9 ±6.1 deg, p=0.01), hip adduction range (12.1 ±5.0 deg vs. 17.5 ±6.9 deg, p=0.01), and hip rotation range (9.9 ±3.1 deg vs. 13.6 ±3.5 deg, p=0.01) were smaller for men than for women. Likewise, distance of mediolateral knee motion (173 ±46 mm vs. 205 ±59 mm, p=0.05) was shorter for men than for women. Kinematics at the trunk and pelvis did not differ between the sexes (p > 0.05).

CONCLUSION: Gender differences in SLS kinematics of healthy young adults appear to apply only at the hip and knee and not at the trunk or pelvis.

346 Board #199 May 29, 9:30 AM - 11:00 AM

Gender and Load Effects on Frontal Plane Kinetics during Single-Leg Drop Landings

Michael E. Feltner, FACSM1, Gerwyn Hughes2, Meghan Pyle1, Courtney Callinan1, Steven Jones1, Jonathan Anthony1, Canaan Tyner1. 1Pepperdine University, Malibu, CA. 2University of Hertfordshire, Hatfield, United Kingdom.

(No relationships reported)

Trunk loading during landing alters the lower extremity biomechanical risk factors associated with anterior cruciate ligament injury.

PURPOSE: To investigate the effects of gender and load on frontal plane kinetics during drop landings.

METHODS: Twenty-two (14 F; 8 M) recreational athletes (21±1 yrs) gave voluntary informed consent and performed single-leg drop landings on the dominant leg during unloaded and loaded (5% body mass) conditions. A weight belt distributed the load in three different conditions relative to the dominant leg: ipsilateral (IPSI), contralateral (CON) and symmetrical. A 10 camera Motion Analysis system (500 Hz) and two Kistler force plates (2000 Hz) collected 3D coordinate and ground reaction force (GRF) data. Inverse dynamics methods computed the resultant joint force (RJF) and torque (RJT) at the ankle, knee and hip. Data were normalized using the subject’s weight (GRF and RJF) or the product of their height (ht) and weight (RJT). Mixed design (2×4) ANOVAs determined the effects of gender and load. A Bonferroni adjustment maintained the experiment-wide error rate at p<0.05 for all statistical comparisons.

RESULTS: No variable exhibited a gender by load interaction or a main effect for gender. The average normalized mediolateral GRF and the RJFs at the ankle and knee exhibited main effects for load (p<0.05). The CON condition exhibited the largest magnitude forces (GRF = 0.07±0.07 BW; Ankle = -0.49±0.15 BW; Knee = -0.18±0.09 BW) and the IPSI condition the smallest (GRF = 0.04±0.06 BW; Ankle = -0.43±0.16 BW; Knee = -0.15±0.07 BW) (positive forces are medial). The average normalized RJTs at the ankle, knee and hip were in the abduction direction and also exhibited main effects for load (p<0.05). The CON condition had the largest magnitude RJTs (Ankle = 0.05±0.02 BW.ht; Knee = 0.05± 0.03 BW.ht; Hip = 0.11±0.04 BW.ht,) and the IPSI condition the smallest (Ankle = 0.04± 0.02 BW.ht; Knee = 0.04± 0.03 BW.ht; Hip = 0.09±0.03 BW.ht).

CONCLUSION: Ipsilateral loading moves the body’s center of mass (CM) toward the landing leg reducing the magnitude of the average medial GRF applied to the foot and resulting in smaller average medial RJFs applied to the distal end of the shank and thigh. In turn, smaller abduction RJTs need to be produced by the muscles of the lower limb to control frontal plane leg motion.

347 Board #200 May 29, 9:30 AM - 11:00 AM

A Comparison of Impulse from Four Loading Configurations

John W. Fox, Jared M. Rehm, Braden H. Romer, Jay H. Patel, Gretchen D. Oliver, FACSM, Wendi H. Weimar. Auburn University, Auburn, AL. (Sponsor: Gretchen D. Oliver, FACSM)

(No relationships reported)

Countermovements are frequently used in athletic events for optimizing performance. Research has shown that the countermovement yields better performances compared to no countermovement.

PURPOSE: This study evaluates impulse of the concentric phase of a ballistic pushup across four preparatory loading configurations.

METHODS: Twenty male participants (83.7±7.4kg; height, 1.8±0.07m) were recruited. The ground reaction force (GRF) was measured during plyometric pushups from the modified push-up position under 4 conditions: [A] was performed from a pre-determined elbow flexed position, [B] similar to a countermovement jump, involved beginning in the modified push-up position then lowering and pushing vertically, [C] standing on one’s knees with arms positioned anteriorly participants fell forward into a countermovement, similar to a depth jump, and [D], beginning from the modified push-up position participants lifted their hands from the ground and fell into a countermovement.

RESULTS: GRF was integrated with respect to time for the concentric phase of each push-up. A 1 (Participant) × 4 (Condition) repeated measures ANOVA was used to analyze differences in impulse during the concentric phase. The analysis indicated that significant differences exist between conditions (F = 101.274, p < .001). Condition C yielded the highest impulse and was significantly higher than all other conditions (p < .001). There was no significant difference between A (288.90±40.57) and B (320.50±74.73) (p < .305). However, impulse during D (381.42±42.34) was greater than A and B (p <.001, p = .004, respectively), but less than C (476.85±60.96) (p < .001).

CONCLUSIONS: The impulse during the concentric phase was enhanced in D and C. However, drop landings are impractical during most athletic events. Hence, this research suggests that the use of a concentric motion prior to a counter movement will enhance ballistic movements.

348 Board #201 May 29, 9:30 AM - 11:00 AM

Limb Loading Asymmetries Of Athletes With Femoroacetabular Impingement During A Drop Vertical Jump Task

Stephanie Di Stasi, Thomas Ellis, Timothy E. Hewett, FACSM. The Ohio State University, Columbus, OH.

(No relationships reported)

PURPOSE: Femoroacetabular impingement (FAI) is a common cause of hip pain in athletic individuals and can severely limit sports-related function. While the clinical presentation of these athletes is becoming clearer, their characteristic neuromuscular behaviors are not well understood. Specifically, the limb loading behaviors of athletes with FAI have yet to be characterized during sports-related tasks. The purpose of this study was to compare the inter-limb differences in loading strategies of athletes diagnosed with FAI during a drop vertical jump. We hypothesized that the involved limb would demonstrate a lower peak vertical ground reaction force (vGRF) and reduced internal hip extensor moment (HEM) compared to the uninvolved limb.

METHODS: Eight subjects (3 males, 5 females; age range: 16-40) who participated in cutting, pivoting, and jumping activities at least 50 hours/year prior to their FAI diagnosis underwent three-dimensional motion analysis of a drop vertical jump (DVJ) task. Peak vGRF and HEM at peak vGRF (both normalized to body weight) during landing were calculated for both limbs. Where effect sizes (ES) exceeded 0.5, paired t-tests were used to determine statistical significance (α=0.05).

RESULTS: Peak vGRF during landing was higher in the involved limb (ES=1.06, P=0.06) when compared to the uninvolved limb (Involved: 1.57 N/BW; 95% CI: 1.36-1.78; Uninvolved:1.38 N/BW; 95%CI: 1.28 -1.48). The average peak vGRF limb-to-limb asymmetry was 21.0% (95%CI: 14.2 - 27.8). There was no difference (ES=0.12) in the HEM between the involved (0.05 N/BW; 95%CI: 0.02 -0.08) and uninvolved (0.05 N/BW; 95% CI: 0.02-0.08) limbs.

CONCLUSIONS: Contrary to our initial hypothesis, peak vGRF was higher in the involved limb than in the uninvolved limb during the landing phase of the DVJ. Data from this preliminary sample indicate that limb loading asymmetries may be characteristic of athletes with FAI. A reduced HEM on the involved limb was not observed, but this may reflect the varied neuromuscular strategies of this small group. Quantification of these limb loading asymmetries may have significant implications on the rehabilitation strategies and return to activity decision-making for this population.

This study was funded by the Sports Section of the APTA.

© 2013 American College of Sports Medicine

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