Studies of the human stretch reflex

We recorded the late electromyographic (EMG) responses to predictable and u npredictable stretches of the wrist flexor and extensor muscles during ball istic movement or isometric contractions. We simultaneously recorded the ac companying cerebral responses. Our findings suggest that the late EMG respo nses are influenced by suprasegmental (cerebral) phasic mechanisms that see m to have a dual functional role, being involved in the control of limb sti ffness and in a servomechanism to return the displaced limb to its intended position. (C) 2000 John Wiley & Sons, Inc.