[Hysteretical properties of muscle contraction during continuous and intermittent efferent stimulation]

Hysteretical effects were studied on the ankle extensor muscle of the anesthetized cat. Continuous and intermittent stimulations were applied to efferents supplying these muscles; linear sinusoidal and step changes of the length were used. Stiffness of the muscle could became negative when the muscle was stretched above the resting length provided that the intermittent stimulation was used. If the same length was achieved under conditions of continuous stimulation, the stiffness was invariably positive. Effectiveness of the intermittent stimulation was higher as compared with continuous one in shortening phases of length changing. The observed hysteretical effects are discussed from the functional point of view.