Abstract
This paper reports strength change of a voluntary contraction when the voluntary motion is synchronized with a stretch reflex induced by involuntary stretch of a muscle. A device developed in this study introduces the stretch reflex on flexor muscles of MP joints by instantaneous extension of the MP joints of four fingers. The device also measure flexion torque of the MP joints and a bioelectric potential (BEP) signal around a forearm. First, it is confirmed by experiments that the reflective force of the stretch reflex becomes bigger when an angular velocity for the instantaneous extension of the MP joints increases. Second, it is found that the contraction force of voluntary flexion is intensified by the stretch reflex synchronization. These results will back up a mechanism of the repetitive facilitation exercise (RFE) that is patient's repetitive exercises of an intended movement accompanied with a facilitation given by a therapist.
