The Effects of Alternating Stimulation Sequences on Isometric Tension and Fatigue Resistance in the Dog Gastrocnemius

In this study we examined the contractile characteristics of the gastrocnemius muscles of six dogs under the isometric condition by applying stimulating pulses to different two motor branches of the tibial nerve. The synchronous and/or the alternating sequences of stimulation were applied to these two motor branches through two pairs of bipolar stainless wire electrodes. In the alternating sequence of supramaximum stimulation at low rates, smooth contraction and higher tension of the gastrocnemius could be obtained and the minimum fusion frequency was lower as compared with the synchronous supramaximum stimulation. In addition, the alternating stimulation sequence could contribute to maintain the isometric tension with higher fatigue resistance, and thus, resulting in shortening the half relaxation time as compared with the synchronous stimulation. These results suggest that the alternating stimulation sequence would be a useful method to realize smooth contraction of the muscles with minimum fatigue.