Effects of hip adductor exertion on EMG activity of the vastus medialis oblique (VMO) and vastus lateralis (VL) DJlUscleds uring: squat exercise

Abstract

A cross sectional study purposed to determine effects of hip adductor exertion on EMG activity of the vastus medialis oblique (VMO) and vastus lateralis (VL) muscles during squat exercise. Thirty healthy young adults without history of anterior knee pain, abnormal knee alignment, quadriceps or others knee injury voluntarily participated in this study. Surface electromyography (EMG) were recorded from the VMO and VL muscles of subject’s dominant leg during squatting without hip adduction, squatting with two sub-maximum and maximum isometric hip adduction (0%, 35%, 70% and 100% hip adductor exertion) exercises. Root mean square (RMS) of EMG activities were normalized by the maximum voluntary isometric contraction (MVC) of each muscle. The multivariate analysis was performed on normalized RMS (%MVC) of the VMO, VL and VMO:VL ratio as dependent variables. A paired t-test was used to evaluate difference between two muscle activities. There were significant effects of hip adductor exertion on the VMO, VL and VMO:VL ratio (p{0.001). During squatting with 35% hip adductor exertion, less VMO but more VL activity than squatting without hip adduction was shown. Squatting with 70% and 100% hip adductor exertion showed more VMO and VL activities than squatting without hip adduction. The VMO:VL ratio presented no significant difference between squatting with 100% hip adductor exertion and squatting without hip adduction. Squatting with 35% and 70% hip adductor exertion demonstrated less VMO:VL ratio than squatting without hip adduction. Paired t-test showed no significant difference between the VMO and VL activities under squatting without hip adduction and squatting with 100% hip adduction. In conclusion, squatting with 70% and 100% isometric hip adductor exertion significantly increases the VMO and VL activities. Squatting without hip adduction and squatting with maximum isometric hip adduction seems to promote balance activities of the VMO and VL muscles, which will benefit to VMO muscle retraining for abnormal patellar tracking