Szepietowski Olivia, Ertman Hanne, Chiou Shin-Yi, Strutton Paul H
The Nick Davey Laboratory, Division of Surgery, Department of Surgery and Cancer, Faculty of Medicine, Sir Michael Uren Hub, Imperial College London, White City Campus, 86 Wood Lane, London W12 0BZ, UK.
Sport, Exercise, and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, UK.
J Electromyogr Kinesiol. 2025 Feb;80:102961. doi: 10.1016/j.jelekin.2024.102961. Epub 2024 Nov 26.
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.
The aim of this study was to investigate use of TMS and the twitch interpolation technique to measure voluntary activation of abdominal muscles.
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).
There was a strong linear relationship between voluntary torque of 50-100 % MVC and TMS-evoked twitch amplitude (r = 0.994, p = 0.035), and voluntary torque between 50-100 % MVC and VA (r = 0.997, p = 0.025). VA at a target torque of 100 % MVC was less than 100 % (86.20 ± 2.29 %).
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.
经颅磁刺激（TMS）已被用于评估肢体和背部肌肉的自主激活（VA），然而其评估腹部肌肉VA的能力尚不清楚。使用TMS评估腹部肌肉VA可应用于躯干功能障碍患者，以进一步了解躯干控制的神经生理学，为实践提供信息，并促进康复计划的制定和监测。
本研究的目的是调查使用TMS和抽搐插值技术测量腹部肌肉的自主激活情况。
20名健康参与者进行了不同水平的等长腹部收缩，在此期间将TMS应用于初级运动皮层。诱发的抽搐以扭矩进行测量，同时从双侧腹直肌、竖脊肌、阔筋膜张肌和股直肌记录表面肌电图（EMG）活动。VA的计算方法为：（1 - 叠加抽搐幅度/估计静息抽搐幅度）×100。估计静息抽搐幅度通过对收缩强度为最大自主收缩（MVC）的50 - 100%时叠加抽搐幅度与扭矩进行线性回归外推计算得出。
50 - 100%MVC的自主扭矩与TMS诱发的抽搐幅度之间存在强线性关系（r = 0.994，p = 0.035），50 - 100%MVC的自主扭矩与VA之间也存在强线性关系（r = 0.997，p = 0.025）。100%MVC目标扭矩下的VA小于100%（86.20±2.29%）。
腹部肌肉的VA可以通过使用TMS的抽搐插值法进行评估。已证明在最大自主收缩期间VA未达到最大值，并且已表明叠加抽搐幅度随收缩强度增加呈线性下降。使用该技术探索躯干肌肉功能有助于提高对躯干控制神经生理学的理解，包括驱动不足的部位，还可改善对与躯干控制功能障碍相关临床病症（如腰痛）治疗方案疗效的监测。
