Russ, D. W., Towse, T. F., Wigmore, D. M., Lanza, I. R., & Kent-Braun, J. A. (2008). Contrasting influences of age and sex on muscle fatigue. Medicine and Science in Sports and Exercise, 40, 234-241.

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This study evaluated fatigue in healthy young (~25+ years) and older (~73+ years) men and women during maximum-effort isometric contractions with a 70% duty cycle (7 seconds of contraction, 3 seconds of rest). Volitional and stimulated force, compound muscle action potential, and muscle contractile responses were collected before, during, and immediately after the fatigue protocol.

At baseline, older Ss had longer force half-relaxation times and less twitch potentiation than younger Ss, consistent with a slower muscle phenotype. During contractions, younger Ss fatigued more than older Ss did, with no differences between men and women. Central activation decreased similarly in all groups with fatigue. There were no fatigue-related differences in peripheral excitation or contractile properties attributable to age or sex.

Implication. There are age-related differences in fatigue during intermittent maximal voluntary contractions with a high duty cycle. The differences are independent of central and peripheral activation. No gender differences were evident in this protocol. Age- and sex-based differences in fatigue seem to arise from distinct mechanisms.

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