Measurement of voluntary activation of abdominal flexors using transcranial magnetic stimulation
File(s)
Published version
Author(s)
Szepietowski, Olivia
Ertman, Hanne
Chiou, Shin-Yi
Strutton, Paul H
Type
Journal Article
Abstract
Background
Transcranial magnetic stimulation (TMS) has been used to assess voluntary activation (VA) of limb and back muscles, however its ability to assess abdominal muscle VA is unknown. The assessment of abdominal muscle VA using TMS could be applied to patients with trunk dysfunction to enable further understanding of the neurophysiology of trunk control, inform practice and enable the development and monitoring of rehabilitation programmes.
Aim
The aim of this study was to investigate use of TMS and the twitch interpolation technique to measure voluntary activation of abdominal muscles.
Methods
Twenty healthy participants performed sets of isometric abdominal contractions of varying levels, during which TMS was applied to the primary motor cortex. The evoked twitches were measured as torque, while simultaneous surface electromyographic (EMG) activity was recorded bilaterally from rectus abdominis, erector spinae, tensor fasciae latae, and rectus femoris. VA was calculated as: (1 – superimposed twitch amplitude/estimated resting twitch amplitude) x 100. Estimated resting twitch amplitude was calculated by extrapolation using linear regression of superimposed twitch amplitude against torque for contraction strengths 50–100 % maximum voluntary contraction (MVC).
Results
There was a strong linear relationship between voluntary torque of 50–100 % MVC and TMS-evoked twitch amplitude (r2 = 0.994, p = 0.035), and voluntary torque between 50–100 % MVC and VA (r2 = 0.997, p = 0.025). VA at a target torque of 100 % MVC was less than 100 % (86.20 ± 2.29 %).
Conclusions
VA of abdominal muscles can be assessed with twitch interpolation using TMS. VA has been shown to be submaximal during maximum voluntary contractions, and it has been demonstrated that superimposed twitch amplitude decreases in a linear fashion with increasing contraction intensity. Using this technique to explore trunk muscle function could help to improve understanding of the neurophysiology of trunk control, including the sites on any deficit in drive and also improve monitoring of the efficacy of treatment regimes for clinical conditions associated with dysfunctions in trunk control e.g. low back pain.
Transcranial magnetic stimulation (TMS) has been used to assess voluntary activation (VA) of limb and back muscles, however its ability to assess abdominal muscle VA is unknown. The assessment of abdominal muscle VA using TMS could be applied to patients with trunk dysfunction to enable further understanding of the neurophysiology of trunk control, inform practice and enable the development and monitoring of rehabilitation programmes.
Aim
The aim of this study was to investigate use of TMS and the twitch interpolation technique to measure voluntary activation of abdominal muscles.
Methods
Twenty healthy participants performed sets of isometric abdominal contractions of varying levels, during which TMS was applied to the primary motor cortex. The evoked twitches were measured as torque, while simultaneous surface electromyographic (EMG) activity was recorded bilaterally from rectus abdominis, erector spinae, tensor fasciae latae, and rectus femoris. VA was calculated as: (1 – superimposed twitch amplitude/estimated resting twitch amplitude) x 100. Estimated resting twitch amplitude was calculated by extrapolation using linear regression of superimposed twitch amplitude against torque for contraction strengths 50–100 % maximum voluntary contraction (MVC).
Results
There was a strong linear relationship between voluntary torque of 50–100 % MVC and TMS-evoked twitch amplitude (r2 = 0.994, p = 0.035), and voluntary torque between 50–100 % MVC and VA (r2 = 0.997, p = 0.025). VA at a target torque of 100 % MVC was less than 100 % (86.20 ± 2.29 %).
Conclusions
VA of abdominal muscles can be assessed with twitch interpolation using TMS. VA has been shown to be submaximal during maximum voluntary contractions, and it has been demonstrated that superimposed twitch amplitude decreases in a linear fashion with increasing contraction intensity. Using this technique to explore trunk muscle function could help to improve understanding of the neurophysiology of trunk control, including the sites on any deficit in drive and also improve monitoring of the efficacy of treatment regimes for clinical conditions associated with dysfunctions in trunk control e.g. low back pain.
Date Issued
2025-02-01
Date Acceptance
2024-11-22
Citation
Journal of Electromyography and Kinesiology, 2025, 80
ISSN
1050-6411
Publisher
Elsevier
Journal / Book Title
Journal of Electromyography and Kinesiology
Volume
80
Copyright Statement
© 2024 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
License URL
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/39637546
PII: S1050-6411(24)00105-6
Subjects
Abdominal
CONTRACTION
Corticospinal
EXCITABILITY
FACILITATION
HUMAN KNEE EXTENSORS
Life Sciences & Biomedicine
LOW-BACK-PAIN
MOTOR
MUSCLE ACTIVATION
Neurosciences
Neurosciences & Neurology
Physiology
POSTURAL RESPONSES
Rehabilitation
Science & Technology
Sport Sciences
STRENGTH
TMS
Transcranial magnetic stimulation
TRUNK FLEXOR
Twitch
Voluntary activation
Publication Status
Published
Coverage Spatial
England
Article Number
102961
Date Publish Online
2024-11-26