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

Keller-Ross-ML; Pereira-HM; Pruse-J; Yoon-T; Schlinder-Delap-B; Nielson-KA; Hunter-SK

J Appl Physiol 2014 Apr; 116(7):767-778

http://dx.doi.org/10.1152/japplphysiol.01129.2013

20045483

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.

Humans; Men; Women; Muscles; Fatigue; Musculoskeletal-system; Muscle-tension; Muscle-stress; Muscle-physiology; Physiology; Physiological-effects; Physiological-function; Physiological-fatigue; Mental-processes; Sex-factors; Age-factors; Age-groups; Author Keywords: gender; muscle fatigue; sex differences; transcranial magnetic stimulation; voluntary activation

M. L. Keller-Ross, Dept. of Cardiovascular Diseases, Mayo Clinic and Foundation, 200 First St., S.W., Rochester, MN 55901

JAPHEV

20140401

Journal Article

keller.manda@mayo.edu

Grant

2014

Grant-Number-T42-OH-008672; M122014

7

8750-7587

Agriculture, Forestry and Fishing

Journal of Applied Physiology

IL; MN

University of Illinois at Chicago