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Cortical Mechanisms of Central Fatigue and Sense of Effort

The purpose of this study was to investigate cortical mechanisms upstream to the corticospinal motor neuron that may be associated with central fatigue and sense of effort during and after a fatigue task. We used two different isometric finger abduction protocols to examine the effects of muscle act...

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Autores principales: Sharples, Simon A., Gould, Jason A., Vandenberk, Michael S., Kalmar, Jayne M.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4747526/
https://www.ncbi.nlm.nih.gov/pubmed/26859391
http://dx.doi.org/10.1371/journal.pone.0149026
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author Sharples, Simon A.
Gould, Jason A.
Vandenberk, Michael S.
Kalmar, Jayne M.
author_facet Sharples, Simon A.
Gould, Jason A.
Vandenberk, Michael S.
Kalmar, Jayne M.
author_sort Sharples, Simon A.
collection PubMed
description The purpose of this study was to investigate cortical mechanisms upstream to the corticospinal motor neuron that may be associated with central fatigue and sense of effort during and after a fatigue task. We used two different isometric finger abduction protocols to examine the effects of muscle activation and fatigue the right first dorsal interosseous (FDI) of 12 participants. One protocol was intended to assess the effects of muscle activation with minimal fatigue (control) and the other was intended to elicit central fatigue (fatigue). We hypothesized that high frequency repetitive transcranial magnetic stimulation (rTMS) of the supplementary motor area (SMA) would hasten recovery from central fatigue and offset a fatigue-induced increase in sense of effort by facilitating the primary motor cortex (M1). Constant force-sensation contractions were used to assess sense of effort associated with muscle contraction. Paired-pulse TMS was used to assess intracortical inhibition (ICI) and facilitation (ICF) in the active M1 and interhemispheric inhibitory (IHI) was assessed to determine if compensation occurs via the resting M1. These measures were made during and after the muscle contraction protocols. Corticospinal excitability progressively declined with fatigue in the active hemisphere. ICF increased at task failure and ICI was also reduced at task failure with no changes in IHI found. Although fatigue is associated with progressive reductions in corticospinal excitability, compensatory changes in inhibition and facilitation may act within, but not between hemispheres of the M1. rTMS of the SMA following fatigue enhanced recovery of maximal voluntary force and higher levels of ICF were associated with lower sense of effort following stimulation. rTMS of the SMA may have reduced the amount of upstream drive required to maintain motor output, thus contributing to a lower sense of effort and increased rate of recovery of maximal force.
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spelling pubmed-47475262016-02-22 Cortical Mechanisms of Central Fatigue and Sense of Effort Sharples, Simon A. Gould, Jason A. Vandenberk, Michael S. Kalmar, Jayne M. PLoS One Research Article The purpose of this study was to investigate cortical mechanisms upstream to the corticospinal motor neuron that may be associated with central fatigue and sense of effort during and after a fatigue task. We used two different isometric finger abduction protocols to examine the effects of muscle activation and fatigue the right first dorsal interosseous (FDI) of 12 participants. One protocol was intended to assess the effects of muscle activation with minimal fatigue (control) and the other was intended to elicit central fatigue (fatigue). We hypothesized that high frequency repetitive transcranial magnetic stimulation (rTMS) of the supplementary motor area (SMA) would hasten recovery from central fatigue and offset a fatigue-induced increase in sense of effort by facilitating the primary motor cortex (M1). Constant force-sensation contractions were used to assess sense of effort associated with muscle contraction. Paired-pulse TMS was used to assess intracortical inhibition (ICI) and facilitation (ICF) in the active M1 and interhemispheric inhibitory (IHI) was assessed to determine if compensation occurs via the resting M1. These measures were made during and after the muscle contraction protocols. Corticospinal excitability progressively declined with fatigue in the active hemisphere. ICF increased at task failure and ICI was also reduced at task failure with no changes in IHI found. Although fatigue is associated with progressive reductions in corticospinal excitability, compensatory changes in inhibition and facilitation may act within, but not between hemispheres of the M1. rTMS of the SMA following fatigue enhanced recovery of maximal voluntary force and higher levels of ICF were associated with lower sense of effort following stimulation. rTMS of the SMA may have reduced the amount of upstream drive required to maintain motor output, thus contributing to a lower sense of effort and increased rate of recovery of maximal force. Public Library of Science 2016-02-09 /pmc/articles/PMC4747526/ /pubmed/26859391 http://dx.doi.org/10.1371/journal.pone.0149026 Text en © 2016 Sharples et al http://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
spellingShingle Research Article
Sharples, Simon A.
Gould, Jason A.
Vandenberk, Michael S.
Kalmar, Jayne M.
Cortical Mechanisms of Central Fatigue and Sense of Effort
title Cortical Mechanisms of Central Fatigue and Sense of Effort
title_full Cortical Mechanisms of Central Fatigue and Sense of Effort
title_fullStr Cortical Mechanisms of Central Fatigue and Sense of Effort
title_full_unstemmed Cortical Mechanisms of Central Fatigue and Sense of Effort
title_short Cortical Mechanisms of Central Fatigue and Sense of Effort
title_sort cortical mechanisms of central fatigue and sense of effort
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4747526/
https://www.ncbi.nlm.nih.gov/pubmed/26859391
http://dx.doi.org/10.1371/journal.pone.0149026
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