[Multiplicity of values for establishment of equilibrium length of an active muscle]

Transition processes of the length changes were studied in the ankle extensors of anesthetized cat. Indetermination was shown to exist in equilibrium length of this muscle. The value of equilibrium length depended on the direction of transition process. Equilibrium length invariably was higher in transition processes of shortening compared with that of lengthening. It has been shown that the observed indetermination of the equilibrium length is connected with hysteretical properties of the muscle contraction.