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Open AccessEditor’s ChoiceArticle

Sustained Isometric Wrist Flexion and Extension Maximal Voluntary Contractions on Corticospinal Excitability to Forearm Muscles during Low-Intensity Hand-Gripping

1
Faculty of Science, Ontario Tech University, Oshawa, ON L1G 0C5, Canada
2
Faculty of Applied Health Sciences, Brock University, St. Catharines, ON L2S 3A1, Canada
3
Faculty of Health Sciences, Ontario Tech University, Oshawa, ON L1G 0C5, Canada
*
Author to whom correspondence should be addressed.
Brain Sci. 2020, 10(7), 445; https://doi.org/10.3390/brainsci10070445
Received: 12 June 2020 / Revised: 6 July 2020 / Accepted: 7 July 2020 / Published: 13 July 2020
(This article belongs to the Special Issue Brain Plasticity and Motor Control—Series II)
The wrist extensors demonstrate an earlier fatigue onset than the wrist flexors. However, it is currently unclear whether fatigue induces unique changes in muscle activity or corticospinal excitability between these muscle groups. The purpose of this study was to examine how sustained isometric wrist extension/flexion maximal voluntary contractions (MVCs) influence muscle activity and corticospinal excitability of the forearm. Corticospinal excitability to three wrist flexors and three wrist extensors were measured using motor evoked potentials (MEPs) elicited via transcranial magnetic stimulation. Responses were elicited while participants exerted 10% of their maximal handgrip force, before and after a sustained wrist flexion or extension MVC (performed on separate sessions). Post-fatigue measures were collected up to 10-min post-fatigue. Immediately post-fatigue, extensor muscle activity was significantly greater following the wrist flexion fatigue session, although corticospinal excitability (normalized to muscle activity) was greater on the wrist extension day. Responses were largely unchanged in the wrist flexors. However, for the flexor carpi ulnaris, normalized MEP amplitudes were significantly larger following wrist extension fatigue. These findings demonstrate that sustained isometric flexion/extension MVCs result in a complex reorganization of forearm muscle recruitment strategies during hand-gripping. Based on these findings, previously observed corticospinal behaviour following fatigue may not apply when the fatiguing task and measurement task are different. View Full-Text
Keywords: transcranial magnetic stimulation; corticospinal excitability; muscle activity; electromyography; fatigue; maximal voluntary contraction; forearm; wrist extension; wrist flexion; isometric transcranial magnetic stimulation; corticospinal excitability; muscle activity; electromyography; fatigue; maximal voluntary contraction; forearm; wrist extension; wrist flexion; isometric
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MDPI and ACS Style

Forman, D.A.; Forman, G.N.; Murphy, B.A.; Holmes, M.W.R. Sustained Isometric Wrist Flexion and Extension Maximal Voluntary Contractions on Corticospinal Excitability to Forearm Muscles during Low-Intensity Hand-Gripping. Brain Sci. 2020, 10, 445. https://doi.org/10.3390/brainsci10070445

AMA Style

Forman DA, Forman GN, Murphy BA, Holmes MWR. Sustained Isometric Wrist Flexion and Extension Maximal Voluntary Contractions on Corticospinal Excitability to Forearm Muscles during Low-Intensity Hand-Gripping. Brain Sciences. 2020; 10(7):445. https://doi.org/10.3390/brainsci10070445

Chicago/Turabian Style

Forman, Davis A.; Forman, Garrick N.; Murphy, Bernadette A.; Holmes, Michael W.R. 2020. "Sustained Isometric Wrist Flexion and Extension Maximal Voluntary Contractions on Corticospinal Excitability to Forearm Muscles during Low-Intensity Hand-Gripping" Brain Sci. 10, no. 7: 445. https://doi.org/10.3390/brainsci10070445

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