USING SYSTEM IDENTIFICATION TECHNIQUES TO STUDY NORMAL AND PATHOLOGICAL NEUROMUSCULAR FUNCTION.

The neuromuscular system controlling the human ankle has been studied. This work makes extensive use of system identification techniques. The work has concentrated on three input/output relations of great importance to neuromuscular control: the relation between position and torque, the dynamic stiffness, which characterizes the overall mechanical operation of the system; the position/EMG relation, which defines the stretch reflex activation of ankle muscles; and the EMG/torque relation, which describes the transformation of muscle activation into mechanical output. Experimental and analytic methods have been established for determining quasilinear models of joint mechanics and stretch reflex dynamics under stationary or slowly varying conditions. These models represent only a part of reflex behavior since they change with the experimental conditions as a result of underlying nonlinearities. Nevertheless, they provide an excellent description of behavior for a given set of conditions.