Reduced neuromuscular activity and force generation during prolonged cycling

A. St Clair Gibson, E. J. Schabort, T. D. Noakes
2001 American Journal of Physiology. Regulatory Integrative and Comparative Physiology  
Reduced neuromuscular activity and force generation during prolonged cycling. Am J Physiol Regulatory Integrative Comp Physiol 281: R187-R196, 2001.-We examined neuromuscular activity during stochastic (variable intensity) 100-km cycling time trials (TT) and the effect of dietary carbohydrate manipulation. Seven endurance-trained cyclists performed two 100-km TT that included five 1-km and four 4-km highintensity epochs (HIE) during which power output, electromyogram (EMG), and muscle glycogen
more » ... nd muscle glycogen data were analyzed. The mean power output of the 4-km HIE decreased significantly throughout the trial from 319 Ϯ 48 W for the first 4-km HIE to 278 Ϯ 39 W for the last 4-km HIE (P Ͻ 0.01). The mean integrated EMG (IEMG) activity during the first 4-km HIE was 16.4 Ϯ 9.8% of the value attained during the pretrial maximal voluntary contraction (MVC). IEMG decreased significantly throughout the trial, reaching 11.1 Ϯ 5.6% during the last 4-km HIE (P Ͻ 0.01). The study establishes that neuromuscular activity in peripheral skeletal muscle falls parallel with reduction in power output during bouts of high-intensity exercise. These changes occurred when Ͻ20% of available muscle was recruited and suggest the presence of a central neural governor that reduces the active muscle recruited during prolonged exercise.
doi:10.1152/ajpregu.2001.281.1.r187 pmid:11404293 fatcat:lovqcdorlndmrlhrhgig52llzy