Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
J Electromyogr Kinesiol. 1997 Mar;7(1):27-37. doi: 10.1016/s1050-6411(96)00016-8.
The electromyogram (EMG) signal has potential as an indicator of stimulated muscle fatigue in applications of functional electrical stimulation (FES). In particular, it could be used to detect near lower limb collapse due to the associated muscle fatigue in FES-aided standing systems and thereby prevent falling. Surface EMG measurement, however, is hampered by stimulation artifact during FES. Modified surface stimulation and EMG detection equipment were designed and built to minimize this artifact and to permit detection of the electrical signal generated by the muscle during contraction. Artifact reduction techniques included shorting stimulator output leads between stimulus pulses and limiting and blanking slew rate in the EMG processing stage. Isometric fatigue experiments were performed by stimulating the quadriceps muscle of 20 able-bodied (a total of 125 trials) and three spinal cord injured (18 trials) subjects. Fatigue-tracking performance indicators were derived from the root-mean-square (RMS) of the EMG amplitude and from the median frequency (MF) of the EMG power spectral content. The results demonstrate that reliable fatigue tracking indicators for practical FES applications will be difficult to obtain, but that amplitude-based measures in spinal cord injured subjects show promise.
肌电图（EMG）信号有可能成为功能性电刺激（FES）应用中受刺激肌肉疲劳的指标。特别是，它可以用于检测由于 FES 辅助站立系统中相关肌肉疲劳而导致的下肢接近瘫痪，从而防止摔倒。然而，表面 EMG 测量受到 FES 期间刺激伪影的影响。设计并制造了改良的表面刺激和 EMG 检测设备，以最大程度地减少这种伪影，并允许检测肌肉在收缩过程中产生的电信号。减少伪影的技术包括在刺激脉冲之间短接刺激器输出引线，以及在 EMG 处理阶段限制和屏蔽转换速率。通过刺激 20 名健康人（共 125 次试验）和 3 名脊髓损伤者（18 次试验）的股四头肌进行等长疲劳实验。疲劳跟踪性能指标源自肌电图幅度的均方根（RMS）和肌电图功率谱内容的中值频率（MF）。结果表明，对于实际的 FES 应用，很难获得可靠的疲劳跟踪指标，但脊髓损伤者的基于幅度的测量指标显示出希望。
