EMG analysis of the vastus medialis/vastus lateralis muscles utilizing the unloaded narrow- and wide-stance squats

The purpose of this study was to see if vastus medialis oblique/vastus lateralis (VMO:VL) ratios could be increased by widening the squat stance and if the VMO activity increases with deeper ranges of knee flexion. Fifteen healthy subjects performed unloaded narrow and wide stance squats through three ranges of knee flexion: 30°, 60°, and 90°. The two squat stances were compared using a 2 x 3 ANOVA to see if the wide-stance squat had any significant difference in EMG activity for VMO:VL ratios compared to the narrow-stance squat. The difference in EMG activity of the VMO between the various angles for both squat stances was also compared. The ANOVA revealed no significant differences between the squat stances for VMO:VL ratios but did show the VMO:VL ratios to be significantly higher with increasing knee flexion angles. These findings suggest that the VMO is active throughout the 90°range and that increasing knee flexion angles can elicit greater activity of the VMO relative to the VL.