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Fatigue and Motor Redundancy: Adaptive Increase in Finger Force Variance in Multi-Finger Tasks
Tarkeshwar Singh, , Vladimir M. Zatsiorsky, Mark L. Latash
Published in American Physiological Society
2010
Volume: 103
   
Issue: 6
Pages: 2990 - 3000
Abstract

Fatigue and motor redundancy: adaptive increase in finger force variance in multi-finger tasks. J Neurophysiol 103: 2990–3000, 2010. First published March 31, 2010; doi:10.1152/jn.00077.2010. We studied the effects of fatigue of the index finger on indices of force variability in discrete and rhythmic accurate force production tasks performed by the index finger and by all four fingers pressing in parallel. An increase in the variance of the force produced by the fatigued index finger was expected. We hypothesized that the other fingers would also show increased variance of their forces, which would be accompanied by co-variation among the finger forces resulting in relatively preserved accuracy of performance. The subjects performed isometric tasks including maximal voluntary contraction (MVC) and accurate force production before and after a 1-min MVC fatiguing exercise by the index finger. During fatigue, there was a significant increase in the root mean square index of force variability during accurate force production by the index finger. In the four-finger tasks, the variance of the individual finger force increased for all four fingers, while the total force variance showed only a modest change. We quantified two components of variance in the space of hypothetical commands to fingers, finger modes. There was a large increase in the variance component that did not affect total force and a much smaller increase in the component that did. The results suggest an adaptive increase in force variance by nonfatigued elements as a strategy to attenuate effects of fatigue on accuracy of multi-element performance. These effects were unlikely to originate at the level of synchronization of motor units across muscle compartments but rather involved higher control levels.

About the journal
PublisherAmerican Physiological Society
Open AccessFalse