Afferent input from the human ankle extensors during walking

In the literature the functional importance of the stretch reflexes of the triceps surae muscle group has been demonstrated with contradictions. E.G. Dietz et al. (1985) found no stretch reflex in the Gastrocnemius medialis (GM) muscle whereas Sinkjaer et al. (1996) reported a clear modulation of the Soleus (SOL) stretch reflex during walking. In this study the short latency stretch reflexes of both the SOL muscle and the GM muscle have been investigated during gait to elaborate on the differences between the muscles of the triceps surae. The stretch reflexes of the GM muscle appear more scattered than the stretch reflexes of the SOL muscle. However, short latency stretch reflexes are reported for both muscles. Secondly. By unloading the ankle extensors during the eccentric contraction in the stance phase, it is investigated to what extent the stretch reflex is part of the locomotor EMG activity during walking. The study demonstrate that afferent feedback from the muscle adds importantly to the locomotor SOL EMG. Judged from the latency, it is probably group II muscle afferents which are the main responsible afferents