SURFACE-DISTRIBUTED LOW-FREQUENCY ASYNCHRONOUS STIMULATION DELAYS FATIGUE OF STIMULATED MUSCLES

Introduction: One important reason why functional electrical stimulation (FES) has not gained widespread clinical use is the limitation imposed by rapid muscle fatigue due to non-physiological activation of the stimulated muscles. We aimed to show that asynchronous low-pulse-rate (LPR) electrical stimulation applied by multipad surface electrodes greatly postpones the occurrence of muscle fatigue compared with conventional stimulation (high pulse rate, HPR). Methods: We compared the produced force vs. time of the forearm muscles responsible for finger flexion in 2 stimulation protocols, LPR (f(L)=10 Hz) and HPR (f(H)=40 Hz). Results: Surface-distributed low-frequency asynchronous stimulation (sDLFAS) doubles the time interval before the onset of fatigue (104 +/- 80%) compared with conventional synchronous stimulation. Conclusions: Combining the performance of multipad electrodes (increased selectivity and facilitated positioning) with sDLFAS (decreased fatigue) can improve many FES applications in both the lower and upper extremities. Muscle Nerve48: 930-937, 2013