Immediate effect of posture-dependent and weight-bearing gluteus medius exercise on muscle function in the lower extremities and dynamic knee valgus

BACKGROUND: The gluteus medius (GM) plays an important role in stabilizing the knee and preventing injury. OBJECTIVE: This study aimed to determine the immediate effects of weight-bearing gluteus medius exercises on lower-extremity muscle function and dynamic knee valgus. METHODS: Eighteen healthy adults (nine each of both sexes) performed three types of weight-bearing gluteus medius exercises (standing, mini-squat, and dead-lift), and a range of kinematic variables were tested in triplicate. Weight-supporting GM exercise consisted of three sets of 15 repetitions of the lateral band walk. The Y-balance test (YBT) and vertical single-leg jump were used as indicators of muscle function in the lower limbs. We used a video analyzer to film the dynamic knee valgus and performed a YBT for the supporting leg and landing leg following a jump. RESULTS: The height of the single-leg vertical jump and the posterolateral and total YBT scores were significantly higher in the dead-lift posture than in the standing and mini-squat postures. Motion analysis of the dead-lifts revealed high hip flexion on the supporting leg in the posterolateral direction, as determined by the YBT, with low levels of internal hip rotation on the landing leg during the one-leg vertical jump. CONCLUSION: As an immediate effect of gluteus medius exercise, the dead-lift posture facilitated single-leg vertical jump, posterolateral balance, and reduced dynamic knee valgus.