Weak associations between hip adduction angle and hip abductor muscle activity during running.

Hip abductor muscle strengthening is often prescribed to reduce the peak hip adduction angle in runners with overuse knee injury. However, no evidence exists associating greater isometric hip abductor muscle strength with smaller peak hip adduction angle during running. Beyond muscle strength, muscle activation patterns may play an important role in controlling joint movement during running. Therefore, the purpose of this investigation was to determine if associations existed among hip adduction angle, hip abductor muscle activity, and isometric hip abductor muscle strength. Twenty-five currently healthy female runners participated. Average gluteus medius muscle activity and tensor fascia lata muscle activity were determined during hip abductor maximal voluntary isometric contractions. Three-dimensional kinematics and hip abductor muscle activity were collected during treadmill running. Dependent variables were analyzed via Pearson product moment correlations. Multi-variable linear regression determined muscle activity's and strength's contributions to the peak hip adduction angle. A fair positive correlation was observed between the peak hip adduction angle and average tensor fascia lata muscle activity magnitude. Additionally, there was a moderate negative correlation between isometric hip abductor muscle strength and average gluteus medius muscle activity magnitude. Tensor fascia lata activity magnitude accounted for the most variance of the peak hip adduction angle. This study adds to the literature which indicates a lack of association between isometric hip abductor muscle strength and peak hip adduction angle in healthy runners. Factors other than hip abductor muscle strength and activation may account for more of the variance in peak hip adduction angles among runners.