Central fatigue explains sex differences in muscle fatigue and contralateral cross-over effects of maximal contractions |
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Authors: | Peter G Martin Jodie Rattey |
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Institution: | (1) Exercise and Sports Science Laboratories, School of Human Movement Studies, Charles Sturt University, Bathurst, Australia;(2) Prince of Wales Medical Research Institute, University of New South Wales, Barker Street, Randwick, Sydney, NSW, 2031, Australia |
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Abstract: | 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. |
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Keywords: | Central fatigue Voluntary activation Fatigue Sex Contralateral Human Quadriceps CNS |
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