Context: Hip-focused interventions are aimed to decrease frontal plane knee loading related to anterior cruciate ligament injuries. Whether a preferred hip landing strategy decreases frontal plane knee loading is unknown. Objective: To determine if a preferred hip landing strategy during a drop vertical jump (DVJ) is utilized during a single-leg landing (SLL) task and whether differences in frontal plane knee loading are consistent between a DVJ and an SLL task. Design: Descriptive laboratory study. Setting: Research laboratory. Participants: Twenty-three collegiate, female soccer players. Main Outcome Measures: Participants were dichotomized into a hip (HIP; n = 9) or knee/ankle (KA; n = 14) strategy group based on the percentage distribution of each lower extremity joint relative to the summated moment (% distribution) during the DVJ. Separate 1-way analysis of variances examined the differences in joint-specific % distribution and external knee abduction moment between the HIP and KA groups. Results: The HIP group had significantly greater % distribution of hip moment and less % distribution of knee moment compared with the KA group during the DVJ and SLL. External knee abduction moment was also significantly less in the HIP group compared with the KA group during the DVJ. Conclusions: Female soccer athletes who land with a preferred hip strategy during a DVJ also land with a preferred hip strategy during an SLL. The preferred hip strategy also resulted in less external knee abduction moments during the DVJ. Clinical Relevance: Targeting the neuromuscular control of the hip extensor may be useful in reducing risk of noncontact anterior cruciate ligament injuries.
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Anh-Dung Nguyen, Jeffrey B. Taylor, Taylor G. Wimbish, Jennifer L. Keith, and Kevin R. Ford
Jeffrey B. Taylor, Anh-Dung Nguyen, Audrey E. Westbrook, Abigail Trzeciak, and Kevin R. Ford
Context: Women’s volleyball requires frequent and repetitive jumping that when performed with altered biomechanics, including kinematic or kinetic asymmetry, may place the athlete at high risk for injury. This study identified and analyzed lower-extremity biomechanical asymmetries in college women’s volleyball players during standard and sport-specific double-leg landing tasks. Design: Cross-sectional laboratory study. Methods: Eighteen female college volleyball players were analyzed using standard 3D motion capture techniques during a drop vertical jump and an unanticipated lateral reactive jump task. Repeated-measures multivariate analysis of variance identified asymmetries in kinematic and kinetic variables of each task. Results: Average symmetry indices ranged from 9.3% to 31.3% during the drop vertical jump and 11.9% to 25.6% during the reactive jump task. During the drop vertical jump, the dominant limb exhibited lower knee abduction moments (P = .03), ankle dorsiflexion moments (P = .02), ankle eversion moments (P = .003) and vertical ground reaction forces (P = .03), and greater ankle inversion moments (P = .001). Both kinematic (λ = 0.27, P = .03) and kinetic (λ = 0.12, P = .008) asymmetries were identified during the reactive jump task. The dominant limb exhibited greater peak knee flexion (P = .003) and ankle dorsiflexion (P = .02) angles, and greater ankle dorsiflexion (P = .005) and inversion (P = .03) moments than the nondominant limb. Conclusions: These asymmetries observed during double-leg landing tasks may predispose volleyball athletes to unilaterally higher ground reaction or muscle forces and ultimately a greater risk of injury during landing.
Jeffrey B. Taylor, Alexis A. Wright, James M. Smoliga, J. Tyler DePew, and Eric J. Hegedus
Physical-performance tests (PPTs) are commonly used in rehabilitation and injury-prevention settings, yet normative values of upper-extremity PPTs have not been established in high-level athletes.
To establish normative data values for the Closed Kinetic Chain Upper-Extremity Stability Test (CKCUEST) and Upper-Quarter Y-Balance Test (UQYBT) in college athletes and compare results between sports and to analyze the relationship between the 2 tests.
257 (118 male, 139 female) Division I athletes participating in basketball, soccer, baseball, lacrosse, volleyball, track and field, and cross-country.
CKCUEST and UQYBT scores were recorded as part of a comprehensive injury-risk screening battery.
Main Outcome Measure:
Pearson correlations assessed the relationship between all measures of the CKCUEST and UQYBT. A factorial ANOVA and a repeated-measures ANOVA (arm dominance) were used to assess interactions between sex, year in school, and sport for CKCUEST and UQYBT scores.
Normative values for the CKCUEST and UQYBT were established for 9 men’s and women’s college sports. No significant relationships were found between PPT scores. Men scored significantly higher than women for the CKCUEST (P = .002) and UQYBT (P = .010). Baseball players scored significantly higher than athletes from all other sports for the UQYBT (P < .001) but showed nonsignificant trends of lower scores for the CKCUEST than lower-extremity-dominant athletes such as runners (P = .063) and lacrosse players (P = .058).
Results suggest that average CKCUEST and UQYBT scores in Division I athletes are distinct from those previously reported in recreationally active populations and that performance differences exist between sexes and sports. In addition, the CKCUEST and UQYBT appear to measure different constructs of performance and may complement each other as part of a screening battery.
Justin P. Waxman, Kevin R. Ford, Anh-Dung Nguyen, and Jeffrey B. Taylor
Vertical stiffness may contribute to lower-extremity injury risk; however, it is unknown whether athletes with different stiffness levels display differences in biomechanics. This study compared differences in biomechanics between female athletes (n = 99) with varying stiffness levels during a repetitive, single-leg, vertical hopping task. Vertical stiffness was calculated as the ratio of peak vertical ground-reaction force to maximum center-of-mass displacement. Tertiles were established using stiffness values, and separate 1-way ANOVAs were used to evaluate between-group differences. Stance times decreased, and flight times, ground-reaction force, and stiffness increased, from the low- to high-stiffness group (P < .050). The high-stiffness group displayed: (1) greater lateral trunk flexion (P = .009) and lesser hip adduction (P = .022) at initial ground contact compared to the low- and moderate-stiffness groups, respectively; (2) lesser peak hip adduction compared to the low-stiffness group (P = .040); (3) lesser lateral trunk-flexion (P = .046) and knee-flexion (P = .010) excursion compared to the moderate- and low-stiffness groups, respectively; and (4) greater peak hip-flexion (P = .001), ankle-dorsiflexion (P = .002), and ankle-eversion (P = .038) moments compared to the low-stiffness group. A wide range of variability in stiffness exists within a relatively homogenous population. Athletes with varying stiffness levels display biomechanical differences that may help identify the potential mechanism(s) by which stiffness contributes to injury risk.
Kevin R. Ford, Anh-Dung Nguyen, Eric J. Hegedus, and Jeffrey B. Taylor
Virtual environments with real-time feedback can simulate extrinsic goals that mimic real life conditions. The purpose was to compare jump performance and biomechanics with a physical overhead goal (POG) and with a virtual overhead goal (VOG). Fourteen female subjects participated (age: 18.8 ± 1.1 years, height: 163.2 ± 8.1 cm, weight 63.0 ± 7.9 kg). Sagittal plane trunk, hip, and knee biomechanics were calculated during the landing and take-off phases of drop vertical jump with different goal conditions. Repeated-measures ANOVAs determined differences between goal conditions. Vertical jump height displacement was not different during VOG compared with POG. Greater hip extensor moment (P < .001*) and hip angular impulse (P < .004*) were found during VOG compared with POG. Subjects landed more erect with less magnitude of trunk flexion (P = .002*) during POG compared with VOG. A virtual target can optimize jump height and promote increased hip moments and trunk flexion. This may be a useful alternative to physical targets to improve performance during certain biomechanical testing, screening, and training conditions.