Author/Editor		McKay, WB; Stokić, DS; Sherwood, AM; Vrbova, G; Dimitrijević, MR
Title		Effect of fatiguing maximal voluntary contraction on excitatory and inhibitory responses elicited by transcranial magnetic motor cortex stimulation
Type		članek
Source		Muscle Nerve
Vol. and No.		Letnik 19, št. 8
Publication year		1996
Volume		str. 1017-24
Language		eng
Abstract		Vertex transcranial magnetic stimulation (TMS) elicited tibialis anterior motor evoked potentials (MEPs) and silent periods (SPs) that were recorded during and following isometric maximal volitional contraction (MVC). During MVC in 6 healthy subjects, MEP amplitudes in the exercised muscle showed an increasing trend from an initial value of 4539 +/- 809 muV (mean +/- SE) to 550 +/- 908 muV (P < 0.13) while force and EMG decreased (P < 0.01). Also, SP duration increased from 165 +/- 37 ms to 231 +/- 32 ms (P < 0.01). Thus, during a fatiguing MVC both excitatory and inhibitory TMS-induced responses increased. TMS delivered during repeated brief 10% MVC contractions before and after a fatiguing MVC in 5 subjects, showed no change in MEP amplitude but SP duration was prolonged after MVC. This SP prolongation was focal to the exercised muscle. Silent periods recorded after pyramidal tract stimulation were unchanged following the MVC. These results suggest that MEP and SP might have common sources of facilitation during an MVC and that inhibitory mechanisms remain focally augmented following a fatiguing MVC.
Descriptors		MOTOR CORTEX MUSCLE CONTRACTION FATIGUE ADULT MIDDLE AGE ELECTRIC STIMULATION ELECTROMYOGRAPHY EVOKED POTENTIALS