Changes of Movement-related Cortical Potentials in Motor Cortex Areas during Exercise-induced Muscle Fatigue

Objective:To examine the changes of movement-related cortical potentials(MRCPs)in motor cortex areas induced by submaximal voluntary isometric fatiguing contractions of flexor digitorum.Methods:15subjects in fatigue group and 13 subjects in non-fatigue group performed 200 repeated 30% MVCs isometric contractions of flexor digitorum,accompanying by measurements of muscle force,surface electromyography(sEMG),and electroencephalography(EEG).The 200 contractions were divided by 4blocks,to observe the changes of maximal handgrip force and RMS of sEMG.And the 200 contractions were divided by 2large blocks,to analyze the MRCPs distracted from EEG.Results:Subjects from the fatigue group during muscle fatigue showed significant decrease of the maximal handgrip force(P<0.001)and RMS of sEMG(P<0.001),accompanying the significant increase of average RMS over 4 blocks.With the development of muscle fatigue,the amplitudes of motor potential(MP)and readiness potential(RP)significantly increased.However,these measurements did not present significant changes.In addition,compared with the non-fatigue group,the MRCPs site in the fatigue group presented the shift to anterior and ipsilateral brain areas.Conclusion:During the muscle fatigue induced by submaximal voluntary isometric contractions of flexor digitorum,the activation strength and activation areas of MRCPs in brain motor cortex areas increases,and the activation site of MRCPs presents a tendency of shift to anterior and ipsilateral brain areas,suggesting a central strategy to compensate the loss of force.In addition,muscle fatigue has more effects on the MP than the RP.