The effects of strength training on the lower extremity biomechanics of female recreational athletes during a stop-jump task

Background: Strength training is considered a strategy for anterior cruciate ligament injury prevention. Little is known about the contribution of strength training to knee and hip biomechanics. Hypothesis: Lower extremity muscle strength training alters knee and hip biomechanics during a stop-jump task. Study Design: Controlled laboratory study. Methods: Knee and hip 3-dimensional kinematic and kinetic data were collected for 66 female recreational athletes ( 33 intervention and 33 control) while performing 3 stop-jump tasks before and after completing a 9-week strength-training program targeting the quadriceps, hamstrings, gluteus medius, and gluteus maximus (intervention) or a 9-week period of no strength training (control). Maximum voluntary isometric contraction strength data were also collected for each subject before the stop-jump tasks in each data collection session. Knee and hip joint angles as well as resultant forces and moments were calculated. Results: The intervention group increased in strength ( P <.001 for all muscles). No significant differences were observed in knee and hip kinematics and kinetics between groups before and after the strength-training protocol. Conclusions: Strength training alone does not alter knee and hip kinematics and kinetics in female recreational athletes. Further research is needed to determine the effect of strength training in combination with other intervention methods on lower extremity biomechanics. Clinical Relevance: Strength training as a single intervention method may not be sufficient to reduce the risk of noncontact anterior cruciate ligament injury in female recreational athletes.