Improvements in Hip Muscle Performance Result in Increased Use of the Hip Extensors and Abductors During a Landing Task

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Background:Impaired hip muscle performance has been implicated as a contributing factor to the increased risk of anterior cruciate ligament (ACL) injury in women.Purpose:To determine the influence of a hip-focused training program on lower extremity biomechanics during a drop-jump task.Study Design:Descriptive laboratory study.Methods:Twenty-one recreationally active women (18-25 years of age) participated in a 4-week training program consisting of hip-focused plyometric and balance perturbation exercises (3 times/wk, 30 min/session). Maximum isometric strength of the hip extensors, hip abductors, and knee extensors was assessed, along with lower extremity biomechanics during a drop-jump task. All assessments were performed within 5 days of initiation and completion of the training program.Results:After training, subjects demonstrated significantly greater maximum isometric strength of the hip extensors (2.87 ± 0.7 vs 3.11 ± 0.7 N-m/kg; P < .01) and hip abductors (2.08 ± 0.7 vs 2.23 ± 0.07 N-m/kg; P = .004). No significant difference in knee extensor strength was observed. After training, subjects landed with significantly greater peak knee flexion (94.0° ± 8.5° vs 98.0° ± 10.1°; P< .001) and hip flexion (83.4° ± 7.6° vs 89.9° ± 8.8°; P = .008) and a lower knee/hip extensor moment ratio (1.33 ± 0.6 vs 0.99 ± 0.3; P = .001). In addition, subjects demonstrated significantly lower peak knee abduction angles (6.8° ± 3.3° vs 5.6° ± 3.1°; P = .04) and average knee adductor moments (0.06 ± 0.1 vs -0.02 ± 0.1 N-m/kg; P < .001).Conclusion:Changes in lower extremity biomechanics consistent with decreased risk for ACL injury were observed after participation in a hip-focused training program.Clinical Relevance:The study results suggest that ACL injury prevention programs targeting hip muscle performance may be important in mitigating biomechanical risk factors associated with ACL injury in women.

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