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Central fatigue as revealed by postexercise decrement of motor evoked potentials
Author(s) -
BrasilNeto Joaquim P.,
Cohen Leonardo G.,
Hallett Mark
Publication year - 1994
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.880170702
Subject(s) - transcranial magnetic stimulation , isometric exercise , brainstem , motor cortex , central nervous system , stimulation , evoked potential , neuromuscular transmission , muscle contraction , muscle fatigue , neuroscience , electromyography , neuromuscular junction , medicine , physical medicine and rehabilitation , psychology
We have previously shown that the amplitudes of motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) were transiently decreased after exercise, indicating fatigue of motor pathways in the central nervous system. The responsible mechanism is apparently decreased efficiency in the generation of the descending volleys in the motor cortex. We also noted a progressive decrement inamplitude from the first to the fourth MEP. To further clarify the mechanism of this phenomenon, 5 subjects were studied with TMS deliveredat the rates of 0.1, 0.15, 0.3, 1, 3, and 6 Hz. The effect was best demonstrated at 0.3 Hz, and occurred after both isometric and isotonic exercise. Three of the subjects also had 0.3‐Hz percutaneous electrical stimulation of the brainstem, and a decrement in MEP amplitude did not occur. Further, the delivery of TMS during muscle contraction after muscle fatigue failed to produce a decrement. The results are similar to those found at the neuromuscular junction in myasthenia gravis and are consistent with a reduced safety factor of cortical synaptic transmission in central nervous system fatigue. © 1994 John Wiley & Sons, Inc.