Fatiguing exercise intensity influences the relationship between parameters reflecting neuromuscular function and postural control variables

PLoS One. 2013 Aug 26;8(8):e72482. doi: 10.1371/journal.pone.0072482. eCollection 2013.

Abstract

The purpose of this study was to investigate the influence of fatiguing exercise intensity on the nature and extent of fatigue-induced changes in neuromuscular function and postural stability in quiet standing. We also explored the contribution of selected neuromuscular mechanisms involved in force production to postural stability impairment observed following fatigue using an approach based on multivariate regressions. Eighteen young subjects performed 30-s postural trials on one leg with their eyes closed. Postural trials were performed before and after fatiguing exercises of different intensities: 25, 50 and 75% of maximal isometric plantarflexor torque. Fatiguing exercises consisted of sustaining a plantarflexor isometric contraction at the target intensity until task failure. Maximal isometric plantarflexor torque, electromyographic activity of plantarflexor and dorsiflexor muscles, activation level (twitch interpolation technique) and twitch contractile properties of plantarflexors were used to characterize neuromuscular function. The 25% exercise was associated with greater central fatigue whereas the 50 and 75% exercises involved mostly peripheral fatigue. However, all fatiguing exercises induced similar alterations in postural stability, which was unexpected considering previous literature. Stepwise multiple regression analyses showed that fatigue-related changes in selected parameters related to neuromuscular function could explain more than half (0.51≤R(2)≤0.82) of the changes in postural variables for the 25% exercise. On the other hand, regression models were less predictive (0.17≤R(2)≤0.73) for the 50 and 75% exercises. This study suggests that fatiguing exercise intensity does not influence the extent of postural stability impairment, but does influence the type of fatigue induced and the neuromuscular function predictors explaining changes in postural variables.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Electromyography
  • Exercise*
  • Female
  • Humans
  • Male
  • Muscle Contraction
  • Muscle, Skeletal / physiology*
  • Physical Exertion*
  • Posture*
  • Regression Analysis
  • Young Adult

Grants and funding

This study was funded in part by the Natural Sciences and Engineering Research Council of Canada (Discovery Grant # 312041-2008 to M. Bilodeau) and the Canada Foundation for Innovation (Leaders Opportunity Fund Award to M. Bilodeau). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.