Li Le, Shin Henry, Li Xiaoyan, Li Sheng, Zhou Ping
Department of Rehabilitation Medicine, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou 510080, China.
Department of Physical Medicine and Rehabilitation, University of Texas Health Science Center at Houston; TIRR Memorial Hermann Research Center, Houston, TX 77030, USA.
Sensors (Basel). 2016 Apr 22;16(4):581. doi: 10.3390/s16040581.
This study assessed changes in electrical impedance myography (EIM) at different levels of isometric muscle contraction as well as during exhaustive exercise at 60% maximum voluntary contraction (MVC) until task failure. The EIM was performed on the biceps brachii muscle of 19 healthy subjects. The results showed that there was a significant difference between the muscle resistance (R) measured during the isometric contraction and when the muscle was completely relaxed. Post hoc analysis shows that the resistance increased at higher contractions (both 60% MVC and MVC), however, there were no significant changes in muscle reactance (X) during the isometric contractions. The resistance also changed during different stages of the fatigue task and there were significant decreases from the beginning of the contraction to task failure as well as between task failure and post fatigue rest. Although our results demonstrated an increase in resistance during isometric contraction, the changes were within 10% of the baseline value. These changes might be related to the modest alterations in muscle architecture during a contraction. The decrease in resistance seen with muscle fatigue may be explained by an accumulation of metabolites in the muscle tissue.
本研究评估了等长肌肉收缩不同水平以及在60%最大自主收缩（MVC）强度下进行力竭运动直至任务失败期间电阻抗肌电图（EIM）的变化。对19名健康受试者的肱二头肌进行了EIM检测。结果显示，等长收缩期间测得的肌肉电阻（R）与肌肉完全放松时存在显著差异。事后分析表明，在较高收缩水平（60%MVC和MVC）时电阻增加，然而，等长收缩期间肌肉电抗（X）没有显著变化。在疲劳任务的不同阶段电阻也发生了变化，从收缩开始到任务失败以及任务失败与疲劳后休息之间电阻均显著降低。虽然我们的结果表明等长收缩期间电阻增加，但变化幅度在基线值的10%以内。这些变化可能与收缩期间肌肉结构的适度改变有关。肌肉疲劳时电阻降低可能是由于肌肉组织中代谢产物的积累所致。
