Muscle activation of vastus medialis obliquus and vastus lateralis during a dynamic leg press exercise with and without isometric hip adduction.

Objectives: To investigate the effects of submaximal and vigorous isometric hip adduction on the vastus medialis obliquus (VMO) and vastus lateralis (VL) activity during the leg press exercise from 90° of knee flexion until full extension.

Design: Experimental.

Setting: University biomechanics laboratory.

Participants: Ten healthy male college students.

Main Outcome Measures: Electromyographic (EMG) activation of VMO, VL and hip adductor longus (HAL) of the dominant leg were recorded during double leg press (LP), leg press with submaximal isometric hip adduction force (LP+), and leg press with vigorous isometric hip adduction force (LP++). The VMO, VL muscle activation, as well as the VMO/VL ratio between different leg press exercises were analyzed by MANOVA over concentric and eccentric phases, and in 15° increments of knee flexion motion. The effect size was calculated.

Results: Neither LP+ nor LP++ changed the overall VMO-VL activation patterns. Specific to knee angle, however, small to medium effect size was shown with incorporation of isometric hip adduction to the leg press exercise for VMO/VL ratio.

Conclusion: Targeted training using the leg press exercise to the last 45° of knee extension/flexion with vigorous hip adduction may be useful in promoting a greater VMO/VL ratio.