title: Central and peripheral fatigue in male cyclists after 4-, 20-, and 40-km time trials.
abstract: OBJECTIVE
  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).
authors: 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.
authors: Kevin
authors: K
authors: Thomas
authors: Stuart
authors: S
authors: Goodall
authors: Mark
authors: M
authors: Stone
authors: Glyn
authors: G
authors: Howatson
authors: Alan
authors: A
authors: St Clair Gibson
authors: Les
authors: L
authors: Ansley
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology*; D004558:Electric Stimulation; D004576:Electromyography; D005221:Fatigue / Q000503:physiopathology*; D005267:Femoral Nerve / Q000502:physiology; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology*; D011712:Pyramidal Tracts / Q000502:physiology; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult