Totally implantable electrodes for FES to measure the muscle fatigue by block stimulation

目的：在电刺激下，肌肉从易疲劳运动单元到抗疲劳运动单元依次收缩（反向招募）。阻滞刺激是一种在电刺激中使神经恢复生理秩序的方法。本研究的目的是研制全植入式电极，并评价低频阻滞刺激坐骨神经对大鼠腓肠肌内侧肌的影响，以减轻这种原始电极对肌肉疲劳的影响。材料：选用Wistar大鼠9只，10只肢体。我们等距测量了大鼠腓肠肌内侧头的收缩力。方法：设定驱动刺激频率为100Hz。三组的脑块刺激频率分别为20、50或100Hz。驱动刺激20秒，阻断刺激2秒后叠加15秒。我们测量了2.4秒、6秒、10秒和14秒的最大强直力，并计算了6秒、10秒和14秒的力量衰减指数，得出了从2.4秒到6、10和14秒的肌肉力量衰减。结果：三个阻断刺激频率均出现阻滞效应。在50 hz和100Hz的阻滞刺激频率下，肌肉疲劳明显低于单纯的驱动刺激（p<0.05）。结论：临床应用功能性电刺激时，阻滞刺激是一种较好的减轻肌肉疲劳的方法。

OBJECTIVE : In electrical stimulation, the muscles contract, in order, from the more fatigable motor units to the fatigue resistant motor units (reverse recruitment). Block stimulation is a method by which to recruitment in the physiological order in electrical stimulation. The purpose of this study were to develop the totally implantabel electrodes and to evaluate the effects of low frequency block stimulation of the sciatic nerve on the medial gastrocnemius muscle of rats an effort to reduce the muscle fatigue using this original electrode.MATERIALS : Ten extremities of nine Wistar rats were used. We isometrically measured the contraction force of the medial head of the gastrocnemius muscle of the rats.METHODS : The frequency of drive stimulation was set at 100Hz. The block stimulation frequency was set at 20, 50 or 100Hz for each of three groups. Drive stimulation was applied for 20 sec, and then 2 sec later, block stimulation was superimposed for 15 sec. We measured maximal tetanic force at 2.4, 6, 10 and 14 sec, and calculated the strength decrement index at 6, 10 and 14 sec to yield the attenuation of muscle force from 2.4 sec to each of 6, 10 and 14 sec.RESULTS : Block effect was seen at all three block stimulation frequencies. Muscle fatigue under block stimulation was significantly less at both 50 and 100Hz block stimulation frequencies than due to drive stimulation only (p<0.05).CONCLUSION : These results suggest that block stimulation is a more favorable method by which to reduce muscle fatigue during clinical use of functional electrical stimulation.