Gender Differences in the Activation and Co-activation of Lower Extremity Muscles During the Stair-to-Ground Descent Transition

Abstract

The movement pattern during stair descent differs by gender, and this difference may be associated with gender differences in muscle strength or activation. The purpose of this study was to determine whether a gender difference in muscle activation exists by comparing the muscle activation amplitude and co-activation of lower extremity muscles during the stair-to-ground descent transition. Fifteen men and thirteen women descended stairs and the muscle activation was measured. Women showed a significantly lower peak normalized electromyography amplitude of the vastus lateralis (women: 171.7% peak EMG activation amplitude for level walking (PEALW), men: 297.0%PEALW, p < 0.05). Additionally, women showed significantly elevated co-activation of the vastus lateralis and biceps femoris compared to men (p < 0.05). The lower amplitude of the vastus lateralis in women indicates lower recruitment of knee extensor. In conclusion, the significantly higher co-activation of the vastus lateralis and biceps femoris in women may be a women’s stair descent strategy to safely descend stairs by increasing knee joint stability and stiffness through less recruitment of knee extensor muscle during stair-to-ground descent transition.