Exploring neuromotor control of the forearm reaction to perturbation

The authors used a sixth-order, two-muscle model of the human forearm position control system to simulate for arm position responses to impulsive torque perturbations. State feedback of muscle length, contraction velocity, and torque model spinal reflex control, while supraspinal control is manifested by changes in feedback gains. Model responses optimized for a time-optimality performance criterion mimic experimentally observed responses, exhibiting familiar triphasic muscle activation patterns which emerge without being explicitly included in the model. Preliminary attempts to fit model responses to experimental data indicate that time-varying reflex loop gains may be necessary