Stability and Parameter Studies of a Stretch Reflex Loop Model

A model of the arm muscle stretch reflex loop is considered. Investigations are carried out on a system consisting of models of the forearm, the muscle spindle in a feedback structure, and the arm muscle. Specifically, the forearm is modeled as an inverted pendulum, the experimentally derived fourth-order muscle spindle model is taken from the literature, and two linear muscle models are employed. The stability of the feedback structure is investigated as a function of various free parameters in the component models. Frequency response profiles are analyzed for the muscle/muscle spindle combination, and are compared to experimentally derived data available in the literature. Finally, digital computer simulations are exhibited for a system corresponding to a quick release experiment, and for a system in which a periodic force is applied to the forearm.