Improvements in hip muscle performance result in increased use of the hip extensors and abductors during a landing task.
BACKGROUND
Impaired hip muscle performance has been implicated as a contributing factor to the increased risk of anterior cruciate ligament (ACL) injury in women.


OBJECTIVE
To determine the influence of a hip-focused training program on lower extremity biomechanics during a drop-jump task.


METHODS
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).


CONCLUSIONS
Changes in lower extremity biomechanics consistent with decreased risk for ACL injury were observed after participation in a hip-focused training program.


CONCLUSIONS
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.
Christopher M. Powers,Division of Biokinesiology and Physical Therapy, University of Southern California, 1540 Alcazar Street, CHP 155, Los Angeles, CA 90089, USA. powers@usc.edu.
Kristen M
KM
Stearns
Christopher M
CM
Powers
D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena / Q000502:physiology; D005260:Female; D006621:Hip Joint / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007718:Knee Injuries / Q000517:prevention & control*; D007719:Knee Joint / Q000502:physiology; D009068:Movement / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D059385:Plyometric Exercise; D004856:Postural Balance / Q000502:physiology*; D055815:Young Adult
ACL injury; hip; landing; training