A sustained voluntary contraction increases central fatigue and produces a 'cross-over' of fatigue during a subsequent contraction of the contralateral limb. These studies compared the magnitude of these changes for men and women. Force and electromyographic responses from dominant (study 1; n=8 men, 8 women) or non-dominant (study 2; n=7 men, 8 women) leg extensors to nerve stimulation were recorded at rest and during brief maximal voluntary contractions (MVCs), before and after 100-s sustained MVCs performed with the dominant leg. For the dominant leg, force was reduced more for men (by ~24%) than women (by ~16%, P<0.05) after the sustained contractions. Similarly, voluntary activation during these contractions was reduced more for men (by ~22%) than women (by ~9%, P<0.05). Conversely, resting twitches changed similarly for both sexes (P>0.05). For the non-dominant leg, men experienced a reduction in force (by ~13%, P<0.001) and had greater deficits in activation than women (~9% vs ~3%, P<0.05), after sustained contractions of the dominant leg. Therefore, sustained MVCs produce greater central fatigue and a more pronounced 'cross-over' of effects to the contralateral limb for men compared to women. These findings demonstrate distinct differences between sexes in the way the nervous system adapts to changes associated with fatigue.
Martin, P. G., & Rattey, J. (2007). Central fatigue explains sex differences in muscle fatigue and contralateral cross-over effects of maximal contractions. Pflugers Archiv European Journal of Physiology, 454(6), 957-969. https://doi.org/10.1007/s00424-007-0243-1