Multi-channel indirect stimulation reduces muscle fatigue

Isometric contraction forces were registered in sheep rectus femoris muscles at two different types of simulation through the femoral nerve. Conventional single-channel nerve stimulation (two electrodes) on one leg was compared with multichannel stimulation (four electrodes with rotating activity) on the contralateral leg. Fatigue indices were evaluated according to R.E. Burke et al. (1973), with stimulation parameters modified for the larger dimensions in sheep. Fatigue indices were calculated after 2, 4, 10, 20, 40, and 60 min. After 2 min, submaximal multichannel stimulation resulted in at least 14% less muscle fatigue compared to single-channel stimulation. Accordingly, after prolonged stimulation up to 60 min, higher contraction forces were recorded at multichannel stimulation. The fatigue indices were 0.43 for single-channel and 0.66 for multichannel stimulation. The data clearly indicate that multichannel stimulation results in 23% less muscle fatigue. The experimental results demonstrate the advantages of multichannel stimulation in patients