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Med Sci Sports Exerc. 2015 Mar;47(3):537-46. doi: 10.1249/MSS.0000000000000448.

Central and peripheral fatigue in male cyclists after 4-, 20-, and 40-km time trials.

Author information

1
1Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle-upon-Tyne, UNITED KINGDOM; 2Department of Sport Management, School of Applied Management and Law, Buckinghamshire New University, High Wycombe, UNITED KINGDOM; 3Water Research Group, School of Environmental Sciences and Development, Northwest University, Potchefstroom, SOUTH AFRICA; and 4School of Medicine, University of the Free State, Bloemfontein, SOUTH AFRICA.

Abstract

PURPOSE:

Few studies have assessed neuromuscular fatigue after self-paced locomotor exercise; moreover, none have assessed the degree of supraspinal fatigue. This study assessed central and peripheral fatigue after self-paced exercise of different durations.

METHODS:

Thirteen well-trained male cyclists completed 4-, 20-, and 40-km simulated time trials (TTs). Pre- and immediately post-TT (<2.5 min), twitch responses from the knee extensors to electrical stimulation of the femoral nerve and transcranial magnetic stimulation of the motor cortex were recorded to assess neuromuscular and corticospinal function.

RESULTS:

Time to complete 4-, 20-, and 40-km TTs was 6.0 ± 0.2, 31.8 ± 1.0, and 65.8 ± 2.2 min at average exercise intensities of 96%, 92%, and 87% of maximum oxygen uptake, respectively. Exercise resulted in significant reductions in maximum voluntary contraction, with no difference between TTs (-18%, -15%, and -16% for 4-, 20-, and 40-km TTs, respectively). Greater peripheral fatigue was evident after 4-km (40% reduction in potentiated twitch) compared with that after 20-km (31%) and 40-km TTs (29%). In contrast, longer TTs were characterized by more central fatigue, with greater reductions in voluntary activation measured by motor nerve (-11% and -10% for 20- and 40-km TTs vs -7% for 4-km TTs) and cortical stimulation (-12% and -10% for 20- and 40-km vs -6% for 4-km).

CONCLUSIONS:

These data demonstrate that fatigue after self-paced exercise is task dependent, with a greater degree of peripheral fatigue after shorter higher-intensity (6 min) TTs and more central fatigue after longer lower-intensity TTs (>30 min).

PMID:
25051388
DOI:
10.1249/MSS.0000000000000448
[Indexed for MEDLINE]

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