Influence of fatigue on hand muscle coordination and EMG-EMG coherence during three-digit grasping

Fingertip force control requires fine coordination of multiple hand muscles within and across the digits. While the modulation of neural drive to hand muscles as a function of force has been extensively studied, much less is known about the effects of fatigue on the coordination of simultaneously ac...

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Bibliographic Details
Published in:Journal of neurophysiology 2010-12, Vol.104 (6), p.3576-3587
Main Authors: Danna-Dos Santos, Alessander, Poston, Brach, Jesunathadas, Mark, Bobich, Lisa R, Hamm, Thomas M, Santello, Marco
Format: Article
Language:English
Subjects:
Adult
Electromyography
Female
Fingers - physiology
Hand - physiology
Hand Strength - physiology
Humans
Isometric Contraction - physiology
Male
Muscle Fatigue - physiology
Muscle, Skeletal - physiology
Young Adult
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Summary:Fingertip force control requires fine coordination of multiple hand muscles within and across the digits. While the modulation of neural drive to hand muscles as a function of force has been extensively studied, much less is known about the effects of fatigue on the coordination of simultaneously active hand muscles. We asked eight subjects to perform a fatiguing contraction by gripping a manipulandum with thumb, index, and middle fingers while matching an isometric target force (40% maximal voluntary force) for as long as possible. The coordination of 12 hand muscles was quantified as electromyographic (EMG) muscle activation pattern (MAP) vector and EMG-EMG coherence. We hypothesized that muscle fatigue would cause uniform changes in EMG amplitude across all muscles and an increase in EMG-EMG coherence in the higher frequency bands but with an invariant heterogeneous distribution across muscles. Muscle fatigue caused a 12.5% drop in the maximum voluntary contraction force (P < 0.05) at task failure and an increase in the SD of force (P < 0.01). Although EMG amplitude of all muscles increased during the fatiguing contraction (P < 0.001), the MAP vector orientation did not change, indicating that a similar muscle coordination pattern was used throughout the fatiguing contraction. Last, EMG-EMG coherence (0-35 Hz) was significantly greater at the end than at the beginning of the fatiguing contraction (P < 0.01) but was heterogeneously distributed across hand muscles. These findings suggest that similar mechanisms are involved for modulating and sustaining digit forces in nonfatiguing and fatiguing contractions, respectively.
ISSN:0022-3077
1522-1598
DOI:10.1152/jn.00583.2010