Department of Mechanical Engineering and Intelligent Systems, the University of Electro-Communications, Tokyo, 182-8585, Japan.
Department of Mechanical Engineering and Intelligent Systems, the University of Electro-Communications, Tokyo, 182-8585, Japan; Center for Neuroscience and Biomedical Engineering, the University of Electro-Communications, Tokyo, 182-8585, Japan.
Med Eng Phys. 2021 Feb;88:9-18. doi: 10.1016/j.medengphy.2020.11.014. Epub 2020 Nov 28.
Functional electrical stimulation (FES) has been an effective treatment option in clinical rehabilitation such as motor function recovery after stroke. The main limitation of FES is the lack of stimulation efficiency in motor unit recruitment compared with voluntary contractions, which may cause the early onset of muscle fatigue. The stimulation efficiency of FES can be improved by optimizing electrode positions to target the motor point (MP). However, the location of MP relative to the skin may shift with the change of muscle geometry during dynamic exercise. Hence, the purpose of this study is to maintain the stimulation efficiency of FES in dynamic exercise by switching the stimulation position to follow the shift of MP. We first measured the shift of the MP of the biceps brachii with respect to the elbow joint angle, and then conducted an experiment to compare four stimulation methods: 2-channel simultaneous stimulation (SS), 2-channel time based shifting stimulation (TSS), 2-channel joint angle based shifting stimulation (JASS), and 3-channel JASS. TSS and JASS were designed as two different MP tracking strategies. The experimental results show that the 3-channel JASS caused the smallest decrease in the maximal elbow angle and the angular velocity. The results also suggest that MP tracking stimulation based on joint angle is effective for the sustainable induction of muscle contraction. Both tracking selectivity and tracking density were shown to be important to improve the stimulation efficiency of FES.
功能性电刺激（FES）在临床康复中是一种有效的治疗选择，例如中风后的运动功能恢复。FES 的主要限制是与自主收缩相比，在运动单位募集方面的刺激效率较低，这可能导致肌肉疲劳的早期发生。通过优化电极位置以针对运动点（MP），可以提高 FES 的刺激效率。然而，MP 相对于皮肤的位置可能会随着动态运动中肌肉几何形状的变化而发生变化。因此，本研究的目的是通过切换刺激位置以跟随 MP 的变化来保持 FES 在动态运动中的刺激效率。我们首先测量了肱二头肌相对于肘关节角度的 MP 偏移，然后进行了一项实验来比较四种刺激方法：双路同时刺激（SS）、双路基于时间的移位刺激（TSS）、双路基于关节角度的移位刺激（JASS）和三路 JASS。TSS 和 JASS 被设计为两种不同的 MP 跟踪策略。实验结果表明，三路 JASS 导致最大肘角和角速度的减小最小。结果还表明，基于关节角度的 MP 跟踪刺激对于可持续诱导肌肉收缩是有效的。跟踪选择性和跟踪密度都被证明对提高 FES 的刺激效率很重要。
