Stressor-induced increase in muscle fatigability of young men and women is predicted by strength but not voluntary activation

Manda L. Keller-Ross, Hugo M. Pereira, Jaclyn Pruse, Tejin Yoon, Bonnie Schlinder-DeLap, Kristy A. Nielson, Sandra K. Hunter

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Abstract

This study investigated mechanisms for the stressor-induced changes in muscle fatigability in men and women. Participants performed an isometric-fatiguing contraction at 20% maximal voluntary contraction (MVC) until failure with the elbow flexor muscles. Study one (n = 55; 29 women) involved two experimental sessions: 1) a high-stressor session that required a difficult mental-math task before and during a fatiguing contraction and 2) a control session with no mental math. For some participants (n = 28; 14 women), cortical stimulation was used to examine mechanisms that contributed to muscle fatigability during the high-stressor and control sessions. Study two (n = 23; nine women) determined the influence of a low stressor, i.e., a simple mental-math task, on muscle fatigability. In study one, the time-to-task failure was less for the high-stressor session than control (P < 0.05) for women (19.4%) and men (9.5%): the sex difference response disappeared when covaried for initial strength (MVC). MVC force, voluntary activation, and peak-twitch amplitude decreased similarly for the control and high-stressor sessions (P < 0.05). In study two, the time-to-task failure of men or women was not influenced by the low stressor (P > 0.05). The greater fatigability, when exposed to a high stressor during a low-force task, was not exclusive to women but involved a strength-related mechanism in both weaker men and women that accelerated declines in voluntary activation and slowing of contractile properties.

Original languageEnglish (US)
Pages (from-to)767-778
Number of pages12
JournalJournal of applied physiology
Volume116
Issue number7
DOIs
StatePublished - Apr 1 2014

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Keywords

  • Gender
  • Muscle fatigue
  • Sex differences
  • Transcranial magnetic stimulation
  • Voluntary activation

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