Movement-related cortical potentials associated with progressive muscle fatigue in a grasping task

Objective: The present research was aimed to further address the general em pirical question regarding the behavioral and neurophysiological indices an d mechanisms that contribute to and/or compensate for muscle fatigue. In pa rticular, we examined isometric force production, EMG, and EEG correlates o f progressive muscle fatigue while subjects performed a grasping task. Methods: Six neurologically healthy subjects were instructed to produce and maintain 70% of maximum voluntary contraction (MVC) for a total of 5 s in a sequence of 120 trials using a specially designed grip dynamometer. Three components of movement-related potentials (Bereitschaftspotential, BP, Mot or potential, MP, and Movement-monitoring potential. MMP) were extracted fr om continuous EEG records and analyzed with reference to behavioral indicat ors of muscle fatigue. Results: Experimental manipulations induced muscle fatigue that was demonst rated by decreases in both MVC values and mean force levels produced concom itant to increases in EMG root mean square (RMS) amplitude with respect to baseline levels, and EMC slope. EEG data revealed a significant increase in MP amplitude at precentral (Cz and FCz) and contralateral (C3) electrode s ites, and increases in BP amplitude at precentral (Cz and FCz) electrode si tes. Conclusions: The increases in EMG amplitude, EMG slope, and MP amplitudes s uggest a possible link. between the control signal originating in the motor cortex and activity level of the alpha -motoneuron pool as a function of p rogressive muscle fatigue. Overall, the data demonstrate that progressive m uscle fatigue induced a systematic increase in the electrocortical activati on over the supplementary motor and contralateral sensorimotor areas as ref lected in the amplitude of movement-related EEG potentials. (C) 2001 Elsevi er Science Ireland Ltd. All rights reserved.