Functional electrical stimulation (FES) has been used to produce force-related activities on the paralyzed muscle among spinal cord injury (SCI) individuals. Early muscle fatigue is an issue in all FES applications. If not properly monitored, overstimulation can occur, which can lead to muscle damage. A real-time mechanomyography (MMG)-based FES system was implemented on the quadriceps muscles of three individuals with SCI to generate an isometric force on both legs. Three threshold drop levels of MMG-root mean square (MMG-RMS) feature (thr50, thr60, and thr70; representing 50%, 60%, and 70% drop from initial MMG-RMS values, respectively) were used to terminate the stimulation session. The mean stimulation time increased when the MMG-RMS drop threshold increased (thr50: 22.7 s, thr60: 25.7 s, and thr70: 27.3 s), indicating longer sessions when lower performance drop was allowed. Moreover, at thr70, the torque dropped below 50% from the initial value in 14 trials, more than at thr50 and thr60. This is a clear indication of muscle fatigue detection using the MMG-RMS value. The stimulation time at thr70 was significantly longer (p = 0.013) than that at thr50. The results demonstrated that a real-time MMG-based FES monitoring system has the potential to prevent the onset of critical muscle fatigue in individuals with SCI in prolonged FES sessions.

中文翻译：

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具有基于机电原理的实时监控，肌肉疲劳检测和安全关闭的电刺激器：一项试点研究。

功能性电刺激（FES）已用于在脊髓损伤（SCI）个体中的瘫痪肌肉上产生与力有关的活动。早期的肌肉疲劳是所有FES应用中的一个问题。如果监测不当，可能会引起过度刺激，从而导致肌肉受损。在三个患有SCI的人的股四头肌上实施了基于实时机械定律（MMG）的FES系统，以在双腿上产生等轴测力。MMG均方根（MMG-RMS）特征的三个阈值下降水平（thr50，thr60和thr70；分别代表与初始MMG-RMS值相比下降50％，60％和70％）会议。当MMG-RMS下降阈值增加时，平均刺激时间增加（thr50：22.7 s，thr60：25.7 s和thr70：27.3 s），表示在允许降低性能的情况下延长会话。此外，在thr70时，扭矩在14次试验中从初始值下降到50％以下，超过thr50和thr60。这是使用MMG-RMS值进行肌肉疲劳检测的明确指示。thr70的刺激时间比thr50的刺激时间长得多（p = 0.013）。结果表明，基于MMG的实时FES监控系统有可能防止长时间FES会话中SCI患者出现严重的肌肉疲劳。