Abstract：
PURPOSE:Greater resistance to muscle fatigue has been observed in women versus men and in older versus young individuals. As suggested mechanisms for these differences include task intensity and duty cycle, the purpose of this study was to evaluate fatigue in healthy young and older men and women during maximum-effort isometric contractions with a 70% duty cycle (7 s of contraction, 3 s of rest). We hypothesized that no differences in fatigue would be observed across age or sex, in contrast to studies incorporating lower duty cycles. METHODS:The protocol was carried out on ankle dorsiflexors of older (73 +/- 1 yr) and younger (25 +/- 1 yr) men and women. Volitional and stimulated force, compound muscle action potential, and muscle contractile responses were collected before, during, and immediately after the fatigue protocol. These measurements allowed for assessment of fatigue as well as central and peripheral activation. RESULTS:At baseline, older subjects had longer force half-relaxation times and less twitch potentiation than younger subjects, consistent with a slower muscle phenotype. During contractions, younger subjects fatigued more than older subjects 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. CONCLUSIONS:These data indicate that age-related differences in fatigue are observed even during intermittent MVC with a high duty cycle, and that these differences are independent of central and peripheral activation. Further, it seems that sex-based differences in both fatigue and central activation failure were abolished with this duty cycle. Overall, these results suggest that age- and sex-based differences in fatigue arise from distinct mechanisms.
journal_name
Med Sci Sports Exercjournal_title
Medicine and science in sports and exerciseauthors
Russ DW,Towse TF,Wigmore DM,Lanza IR,Kent-Braun JAdoi
10.1249/mss.0b013e31815bbb93subject
Has Abstractpub_date
2008-02-01 00:00:00pages
234-41issue
2eissn
0195-9131issn
1530-0315journal_volume
40pub_type
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journal_title：Medicine and science in sports and exercise
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journal_title：Medicine and science in sports and exercise
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