The Effects of Feedback with and without Strength Training on Lower Extremity Biomechanics

BACKGROUND: Feedback instruction is a proven modality for the alteration of motion patterns. There are no existing data on the contribution of strength training, when combined with feedback instruction, to the altering of lower extremity biomechanics. HYPOTHESIS: Lower extremity muscle strength training provides an increased capacity to alter knee and hip biomechanics during a stop-jump task in response to a feedback protocol. STUDY DESIGN: Controlled laboratory study. METHODS: Knee and hip 3-dimensional kinematic and kinetic data were collected for 58 female recreational athletes while performing 3 stop-jump tasks after completing a 9-week strength training program (ST-FB; n = 29) or a 9-week period of no strength training (FB; n = 29). Data were then collected for both groups after completing a jump-landing feedback instruction protocol. Knee and hip joint angles, as well as resultant forces and moments, were calculated. RESULTS: Across all participants, there were decreased peak vertical ground-reaction forces (P < .001) and increased knee flexion (P = .050), hip flexion (P < .001), and hip abduction (P = .032) angles, subsequent to the feedback protocol. Hip abduction angle (P < .001) increased in the ST-FB group but not the FB group, and peak knee anterior shear force (P = .015) decreased in the ST-FB group but increased in the FB group (P = .009). CONCLUSION: The results indicate that strength training, when used in conjunction with video-assisted feedback, may provide an increased capacity for the alteration of knee and hip biomechanics. CLINICAL RELEVANCE: Programs that include both strength training and movement education through feedback may be necessary to increase the effectiveness of anterior cruciate ligament prevention programs. Strength training may provide an increased capacity for athletes to respond to other intervention modalities used in anterior cruciate ligament injury prevention programs.