Alterations in corticospinal excitability with imposed vs. voluntary fatigue in human hand muscles

Department of Physiology, Adelaide University, Adelaide, South Australia 5005, Australia We aimed to determine whether postexercise depression of motor-evoked potentials (MEPs) could be demonstrated without voluntary muscle activation in humans. Voluntary fatigue was induced with a 2-min maximal vol...

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Bibliographic Details
Published in:Journal of applied physiology (1985) 2002-05, Vol.92 (5), p.2131-2138
Main Authors: Pitcher, Julia B, Miles, Timothy S
Format: Article
Language:English
Subjects:
Adolescent
Adult
Biological and medical sciences
Electric Stimulation
Electromyography
Electroshock
Evoked Potentials, Motor - physiology
Exercise
Fatigue
Female
Fundamental and applied biological sciences. Psychology
Hand - physiology
Humans
Male
Middle Aged
Motor ability
Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration
Muscle Fatigue - physiology
Muscle, Skeletal - physiology
Neuronal Plasticity - physiology
Physical Exertion - physiology
Pyramidal Tracts - physiology
Reaction Time
Vertebrates: nervous system and sense organs
Volition - physiology
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Summary:Department of Physiology, Adelaide University, Adelaide, South Australia 5005, Australia We aimed to determine whether postexercise depression of motor-evoked potentials (MEPs) could be demonstrated without voluntary muscle activation in humans. Voluntary fatigue was induced with a 2-min maximal voluntary contraction (MVC) of the first dorsal interosseous (FDI) muscle. On another occasion, "electrical fatigue" was induced with trains of shocks delivered for 2 min over the FDI motor point. Five of the twelve subjects also underwent "sequential fatigue" consisting of a 2-min MVC of FDI followed by 20 min of rest and then 2 min of motor point stimulation. Voluntary fatigue induced MEP depression that persisted for at least 20 min. Electrical fatigue induced a transient MEP facilitation that subsided 20   min after the stimulation and became depressed within 30 min. Thus MEP depression can be induced by both voluntary and electrical fatigue. With electrical fatigue, the initial depression is "masked" by transient MEP facilitation, reflecting cortical plasticity induced by the prolonged electrical stimulation. MEP depression probably reflects tonic afferent input from the exercising muscle that alters cortical excitability without altering spinal excitability. transcranial magnetic stimulation; motor cortex; afferents; plasticity; motor-evoked potential
ISSN:8750-7587
1522-1601
DOI:10.1152/japplphysiol.00835.2001