Effects of neuromuscular fatigue on electromechanical delay of the leg extensors and flexors in young men and women

INTRODUCTION: We examined the effects of neuromuscular fatigue on volitional electromechanical delay (EMD) of leg extensors and flexors between genders. METHODS: Twenty-one men and 20 women performed 2 maximal voluntary contractions (MVCs), followed by intermittent isometric contractions of leg extensors and flexors using a 0.6 duty cycle (6-s contraction, 4-s relaxation) at 50% of MVC until volitional fatigue was achieved. MVCs were again performed at 0, 7, 15, and 30 min post-fatigue. RESULTS: EMD was greater compared with baseline at all post-fatigue time phases for the leg flexors (P = 0.001-0.007), while EMD was greater at Post0, Post15 and Post30 (P = 0.001-0.023) for the leg extensors. EMD was also greater for leg extensors compared with leg flexors only at Post0. CONCLUSION: No differential gender-related fatigue effects on EMD were shown. There were different fatigue-induced responses between leg extensors and flexors, with leg extensors exhibiting higher EMD immediately post-fatigue.