Fatiguing Exercise Intensity Influences the Relationship between Parameters Reflecting Neuromuscular Function and Postural Control Variables

• Published in: PloS one Vol. 8; no. 8; p. e72482
• Main Authors: Boyas, Sébastien, Remaud, Anthony, Rivers, Erin, Bilodeau, Martin
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 26.08.2013; Public Library of Science (PLoS)
• Subjects: Adult; Aging; Ankle; Biology; Contractility; Contraction; Electromyography; EMG; Exercise; Exercise intensity; Fatigue; Fatigue failure; Female; Health sciences; Humans; Impairment; Influence; Interpolation; Isometric; Laboratories; Life Sciences; Male; Materials fatigue; Mathematics; Medicine; Muscle Contraction; Muscle, Skeletal - physiology; Muscles; Neuromuscular system; Physical Exertion; Physical fitness; Physiology; Posture; Regression Analysis; Regression models; Stability analysis; Studies; Torque; Young Adult
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0072482

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.