Cargando…

Ankle Joint Angle Influences Relative Torque Fluctuation during Isometric Plantar Flexion

The purpose of this study was to investigate the influence of changes in muscle length on the torque fluctuations and on related oscillations in muscle activity during voluntary isometric contractions of ankle plantar flexor muscles. Eleven healthy individuals were asked to perform voluntary isometr...

Descripción completa

Detalles Bibliográficos
Autores principales: Shi, Fandi, Rymer, William Zev, Son, Jongsang
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2023
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10045061/
https://www.ncbi.nlm.nih.gov/pubmed/36978764
http://dx.doi.org/10.3390/bioengineering10030373
_version_ 1784913504301481984
author Shi, Fandi
Rymer, William Zev
Son, Jongsang
author_facet Shi, Fandi
Rymer, William Zev
Son, Jongsang
author_sort Shi, Fandi
collection PubMed
description The purpose of this study was to investigate the influence of changes in muscle length on the torque fluctuations and on related oscillations in muscle activity during voluntary isometric contractions of ankle plantar flexor muscles. Eleven healthy individuals were asked to perform voluntary isometric contractions of ankle muscles at five different contraction intensities from 10% to 70% of maximum voluntary isometric contraction (MVIC) and at three different muscle lengths, implemented by changing the ankle joint angle (plantar flexion of 26°-shorter muscle length; plantar flexion of 10°-neutral muscle length; dorsiflexion of 3°-longer muscle length). Surface electromyogram (EMG) signals were recorded from the skin surface over the triceps surae muscles, and rectified-and-smoothed EMG (rsEMG) were estimated to assess the oscillations in muscle activity. The absolute torque fluctuations (quantified by the standard deviation) were significantly higher during moderate-to-high contractions at the longer muscle length. Absolute torque fluctuations were found to be a linear function of torque output regardless of muscle length. In contrast, the relative torque fluctuations (quantified by the coefficient of variation) were higher at the shorter muscle length. However, both absolute and relative oscillations in muscle activities remained relatively consistent at different ankle joint angles for all plantar flexors. These findings suggest that the torque steadiness may be affected by not only muscle activities, but also by muscle length-dependent mechanical properties. This study provides more insights that muscle mechanics should be considered when explaining the steadiness in force output.
format Online
Article
Text
id pubmed-10045061
institution National Center for Biotechnology Information
language English
publishDate 2023
publisher MDPI
record_format MEDLINE/PubMed
spelling pubmed-100450612023-03-29 Ankle Joint Angle Influences Relative Torque Fluctuation during Isometric Plantar Flexion Shi, Fandi Rymer, William Zev Son, Jongsang Bioengineering (Basel) Article The purpose of this study was to investigate the influence of changes in muscle length on the torque fluctuations and on related oscillations in muscle activity during voluntary isometric contractions of ankle plantar flexor muscles. Eleven healthy individuals were asked to perform voluntary isometric contractions of ankle muscles at five different contraction intensities from 10% to 70% of maximum voluntary isometric contraction (MVIC) and at three different muscle lengths, implemented by changing the ankle joint angle (plantar flexion of 26°-shorter muscle length; plantar flexion of 10°-neutral muscle length; dorsiflexion of 3°-longer muscle length). Surface electromyogram (EMG) signals were recorded from the skin surface over the triceps surae muscles, and rectified-and-smoothed EMG (rsEMG) were estimated to assess the oscillations in muscle activity. The absolute torque fluctuations (quantified by the standard deviation) were significantly higher during moderate-to-high contractions at the longer muscle length. Absolute torque fluctuations were found to be a linear function of torque output regardless of muscle length. In contrast, the relative torque fluctuations (quantified by the coefficient of variation) were higher at the shorter muscle length. However, both absolute and relative oscillations in muscle activities remained relatively consistent at different ankle joint angles for all plantar flexors. These findings suggest that the torque steadiness may be affected by not only muscle activities, but also by muscle length-dependent mechanical properties. This study provides more insights that muscle mechanics should be considered when explaining the steadiness in force output. MDPI 2023-03-18 /pmc/articles/PMC10045061/ /pubmed/36978764 http://dx.doi.org/10.3390/bioengineering10030373 Text en © 2023 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Shi, Fandi
Rymer, William Zev
Son, Jongsang
Ankle Joint Angle Influences Relative Torque Fluctuation during Isometric Plantar Flexion
title Ankle Joint Angle Influences Relative Torque Fluctuation during Isometric Plantar Flexion
title_full Ankle Joint Angle Influences Relative Torque Fluctuation during Isometric Plantar Flexion
title_fullStr Ankle Joint Angle Influences Relative Torque Fluctuation during Isometric Plantar Flexion
title_full_unstemmed Ankle Joint Angle Influences Relative Torque Fluctuation during Isometric Plantar Flexion
title_short Ankle Joint Angle Influences Relative Torque Fluctuation during Isometric Plantar Flexion
title_sort ankle joint angle influences relative torque fluctuation during isometric plantar flexion
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10045061/
https://www.ncbi.nlm.nih.gov/pubmed/36978764
http://dx.doi.org/10.3390/bioengineering10030373
work_keys_str_mv AT shifandi anklejointangleinfluencesrelativetorquefluctuationduringisometricplantarflexion
AT rymerwilliamzev anklejointangleinfluencesrelativetorquefluctuationduringisometricplantarflexion
AT sonjongsang anklejointangleinfluencesrelativetorquefluctuationduringisometricplantarflexion