Vastus Lateralis and Vastus Medialis Obliquus Activity During a Straight-Leg Raise and Knee Extension With Lateral Hip Rotation

Objective: To compare average electromyogram (EMG) activity of the vastus medialis obliquus (VMO) and vastus lateralis (VL) during straight-leg raise (SLR) and knee extension (KE) with the hip in neutral and lateral rotation. Design: 1  4 factorial repeated-measures. Setting: Laboratory. Participants: 13 male college students. Intervention: SLR with hip flexed at 40°, in neutral position, and maximally laterally rotated and KE with hip in neutral and maximally laterally rotated. Main Outcome Measure: Average EMG activity during each of the 4 conditions, normalized against peak muscle activity during that trial. Results: No differences were observed between exercises in VMO activity (F3,36 = 0.646, P > .05), VL activity (F3,36 = 1.08, P > .05), or VMO:VL ratio (F3,36 = 0.598, P > .05). Conclusions: Electrical activity of the VMO or VL and VMO:VL ratio do not change with hip position or exercise.