The Effect of Altering Knee Position and Squat Depth on VMO : VL EMG Ratio During Squat Exercises

Abstract

Background: Patellofemoral pain syndrome is an extremely common condition, believed to be caused by altered activation of vastus medialis obliquus (VMO), leading to maltracking of the patella.

Aim: This study aimed to investigate the effect of altering knee movement and squat depth on the ratio of VMO and vastus lateralis (VMO : VL) during squat exercises.

Method: Eighteen (7 male and 11 female) healthy, asymptomatic participants performed semi-squat exercises with three squat depths (20°, 50° and 80° of knee flexion) while following three knee movement paths (neutral, varus or valgus). Normalized VMO : VL ratio from linear envelope surface electromyography was analysed.

Results: No significant effect was found for gender (p = 0.87), leg dominance (p = 0.99) or knee position (p = 0.44). A significant effect was found for squat depth (p < 0.001) with both the 50° and 80° squats showing increases in VMO : VL ratio (p = 0.031 and p = 0.028), respectively. The VMO : VL ratio was not influenced by gender, leg dominance or knee position in semi-squat exercises.

Discussion and conclusion: Increases in relative VMO activation did occur in 'deeper' squat depths (50° and 80° knee flexion) compared with the 20° condition. Further research is needed in this area concerning the effects of such exercise modifications on a symptomatic patellofemoral pain syndrome population. Copyright © 2015 John Wiley & Sons, Ltd.

Keywords: patellofemoral joint; squat exercises; vastus lateralis; vastus medialis obliquus.