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

目的：在电刺激中，肌肉按顺序收缩，从更易疲劳的运动单位到耐疲劳的运动单位(反向募集)。阻断刺激是电刺激中按生理顺序进行募集的一种方法。本研究的目的是研制完全埋置电极，并评价低频阻断刺激坐骨神经对大鼠腓肠肌内侧肌的影响，以减轻肌肉疲劳。材料：选用Wistar大鼠9只10条肢体。等长测量大鼠腓肠肌内侧头的收缩力。方法：驱动刺激频率设为100 Hz。三组的阻断刺激频率分别为20、50、100赫兹。驱动刺激20s，2s后叠加块刺激15s。测定2.4、6、10、14秒的最大强直力，计算6、10、14秒的肌力衰减指数，得出2.4秒至6、10、14秒的肌力衰减。在50和100赫兹的块刺激频率下，块刺激下的肌肉疲劳均明显低于单纯驱动刺激下的肌肉疲劳(P&lt；0.05)。结论：在临床应用功能性电刺激时，块刺激是一种更有利于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.