Reflex and Non-Reflex Stiffness of Soleus Muscle in the Cat

Abstract

The apparent mechanical properties of the soleus muscle in the cat are significantly modified when autogenetic reflex connections around the muscle are intact. The apparent steady-state stiffness of the muscle is increased when a fraction of its motor units are activated. In the transient response to muscle stretch, autogenetic reflexes not only increase the apparent stiffness of the muscle, but also mask sudden reductions in force which occur in the absence of reflexes. The reflexes are fast enough to mask these reductions up to stretch velocities of at least 85 mm/sec.