Studies in Postural Control Systems Part II: Tendon Jerk Input

The postural control system in normal humans is studied by applying a tendon jerk disturbance to the system. A stretch reflex was elicited in the gastrocnemius-soleus muscle by a tap on the achilles tendon. It is shown that the initial conditions (muscle tension or the length of the muscle) and the stimulus (strength of the hammer force) have strong influence on the reflex response (change in foot torque or angle).