| Abstract: | The principle nonlinear characteristics of changes in the length of active (soleus, gastrocnemius, and plantaris) muscle resulting from controlled changes in external load were examined during acute experiments on anesthetized cats. Summation of successive muscle responses to repetitive phased changes in load was shown to be absent due to hysteresis effects; this does not satisfy the principles of superposition and leads to an important functional result: the muscle exerts a stabilizing effect on overall motor system dynamics, limiting unwanted shifts in joint angles during variation in external load. A relationship between the trajectory profile of change in muscle length and the lead-up to the movement arises due to muscle contraction hysteresis. Velocity at the initial stage of movement was always higher when the latter was preceded by motion in the same direction. The functional significance of the nonlinear properties of active muscle movement accompanying changing external load is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 20, No. 6, pp. 736–743, November–December, 1988. |
