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

journal contribution
posted on 2002-05-01, 00:00 authored by Julia Pitcher, Timothy S Miles
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.

History

Journal

Journal of Applied Physiology

Volume

92

Issue

5

Pagination

2131 - 2138

Publisher

American Physiological Society

Location

United States

ISSN

8750-7587

eISSN

1522-1601

Language

en

Publication classification

C1 Refereed article in a scholarly journal