Cargando…

Differences in motor unit firing properties of the vastus lateralis muscle during postural and voluntary tasks

The firing properties of the motor units are usually affected by the motor task. However, it has not been clarified whether the firing properties of the motor units of a specific muscle are different between postural and voluntary tasks. Therefore, this study investigated whether the recruitment and...

Descripción completa

Detalles Bibliográficos
Autores principales: Aoyama, Toshiyuki, Kohno, Yutaka
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9561828/
https://www.ncbi.nlm.nih.gov/pubmed/36246135
http://dx.doi.org/10.3389/fphys.2022.955912
_version_ 1784808032444612608
author Aoyama, Toshiyuki
Kohno, Yutaka
author_facet Aoyama, Toshiyuki
Kohno, Yutaka
author_sort Aoyama, Toshiyuki
collection PubMed
description The firing properties of the motor units are usually affected by the motor task. However, it has not been clarified whether the firing properties of the motor units of a specific muscle are different between postural and voluntary tasks. Therefore, this study investigated whether the recruitment and rate coding of the motor units differ between these two motor tasks. Thirteen healthy volunteers performed trapezoidal muscle contraction with a target value of 15% maximum electromyography (EMG) activity by voluntary left knee extension in the sitting position (voluntary task) and postural maintenance in the semi-squatting position (postural task) with a knee flexion angle of 30°. We obtained four channels of surface EMG activity during each task from left vastus lateralis muscle. We extracted the firing properties of individual motor units using the EMG decomposition algorithm. The recruitment threshold and motor unit action potential amplitude were significantly lower in the postural task than in the voluntary task, and conversely, the mean firing rate was significantly higher. These results were explained by the preferential recruitment of motor units with higher recruitment threshold and amplitude in the voluntary task, while motor units with lower recruitment threshold and higher firing rate were preferentially recruited in the postural task. Preferential activation of fatigue-resistant motor units in the postural task is a reasonable strategy as it allows for sustained postural maintenance. We provide the first evidence that motor unit firing properties are clearly different between postural and voluntary tasks, even at the same muscle activity level.
format Online
Article
Text
id pubmed-9561828
institution National Center for Biotechnology Information
language English
publishDate 2022
publisher Frontiers Media S.A.
record_format MEDLINE/PubMed
spelling pubmed-95618282022-10-15 Differences in motor unit firing properties of the vastus lateralis muscle during postural and voluntary tasks Aoyama, Toshiyuki Kohno, Yutaka Front Physiol Physiology The firing properties of the motor units are usually affected by the motor task. However, it has not been clarified whether the firing properties of the motor units of a specific muscle are different between postural and voluntary tasks. Therefore, this study investigated whether the recruitment and rate coding of the motor units differ between these two motor tasks. Thirteen healthy volunteers performed trapezoidal muscle contraction with a target value of 15% maximum electromyography (EMG) activity by voluntary left knee extension in the sitting position (voluntary task) and postural maintenance in the semi-squatting position (postural task) with a knee flexion angle of 30°. We obtained four channels of surface EMG activity during each task from left vastus lateralis muscle. We extracted the firing properties of individual motor units using the EMG decomposition algorithm. The recruitment threshold and motor unit action potential amplitude were significantly lower in the postural task than in the voluntary task, and conversely, the mean firing rate was significantly higher. These results were explained by the preferential recruitment of motor units with higher recruitment threshold and amplitude in the voluntary task, while motor units with lower recruitment threshold and higher firing rate were preferentially recruited in the postural task. Preferential activation of fatigue-resistant motor units in the postural task is a reasonable strategy as it allows for sustained postural maintenance. We provide the first evidence that motor unit firing properties are clearly different between postural and voluntary tasks, even at the same muscle activity level. Frontiers Media S.A. 2022-09-30 /pmc/articles/PMC9561828/ /pubmed/36246135 http://dx.doi.org/10.3389/fphys.2022.955912 Text en Copyright © 2022 Aoyama and Kohno. https://creativecommons.org/licenses/by/4.0/This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Physiology
Aoyama, Toshiyuki
Kohno, Yutaka
Differences in motor unit firing properties of the vastus lateralis muscle during postural and voluntary tasks
title Differences in motor unit firing properties of the vastus lateralis muscle during postural and voluntary tasks
title_full Differences in motor unit firing properties of the vastus lateralis muscle during postural and voluntary tasks
title_fullStr Differences in motor unit firing properties of the vastus lateralis muscle during postural and voluntary tasks
title_full_unstemmed Differences in motor unit firing properties of the vastus lateralis muscle during postural and voluntary tasks
title_short Differences in motor unit firing properties of the vastus lateralis muscle during postural and voluntary tasks
title_sort differences in motor unit firing properties of the vastus lateralis muscle during postural and voluntary tasks
topic Physiology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9561828/
https://www.ncbi.nlm.nih.gov/pubmed/36246135
http://dx.doi.org/10.3389/fphys.2022.955912
work_keys_str_mv AT aoyamatoshiyuki differencesinmotorunitfiringpropertiesofthevastuslateralismuscleduringposturalandvoluntarytasks
AT kohnoyutaka differencesinmotorunitfiringpropertiesofthevastuslateralismuscleduringposturalandvoluntarytasks