[Analysis of muscle movement during efferent frequency-modulated activation]

Main properties of muscle movements evoked by changes in frequency of distributed stimulation of the efferents were studied on the soleus and plantaris muscles of anesthetized cats. It has been shown possible in principle to describe the evoked movements in terms of the previously elaborated nonlinear model of muscle dynamics. The model consisted of hysteretical statics and a linear dynamic element whose parameters varied with changes in direction of the movement; hysteretical slowing down of the movements was more pronounced in the elongation reactions evoked by a decrease of the stimulation frequency. Hysteresis of the muscle contraction was also shown to be mainly responsible for interaction of the two inputs (frequency of the efferent stimulation and external load). Nonlinear effects of the efferent control of the muscle contraction are discussed from the functional point of view.