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

目的：在电刺激中，肌肉按顺序从较疲劳的运动单位收缩到抗疲劳的运动单位（反向募集）。阻断刺激是一种方法，通过该方法在电刺激中以生理顺序募集。本研究的目的是研制完全可拆卸的电极，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，以减轻肌肉疲劳。材料：Wistar大鼠9只，10条肢体。方法：采用等长法测量大鼠腓肠肌内侧头的收缩力。将三组中的每一组的阻滞刺激频率设置为20、50或100Hz。施加驱动刺激20秒，然后2秒后，叠加阻滞刺激15秒。我们在2.4，6，10和14秒测量最大强直力，并计算在6，10和14秒的强度衰减指数，以产生从2.4秒到6，10和14秒的肌肉力量衰减。结果：在所有三个阻滞刺激频率下均观察到阻滞效应。在50 Hz和100 Hz阻滞刺激频率下，阻滞刺激引起的肌肉疲劳明显低于单纯驱动刺激（p<0.05）。结论：阻滞刺激是临床应用功能性电刺激时减轻肌肉疲劳的一种较好的方法。

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.