Reorganization of flexion reflexes in the upper extremity of hemiparetic subjects

We examined spatiotemporal abnormalities in the flexor reflex response in t he impaired upper extremity of hemiparetic subjects. Electrical stimulation was used to elicit flexion reflexes in both upper extremities of 8 hemipar etic brain-injured and 6 control subjects. Electromyograms (EMGs) were reco rded from 12 arm muscles, and reflex forces and moments were recorded at th e wrist with a load cell, and converted to shoulder and elbow torques. We f ound that the onset of reflex torque and EMG was delayed in the impaired ar m and delays were greater at the shoulder than at the elbow. The normal ref lex torque response consisted of elbow flexion, shoulder extension, and sho ulder adduction. In contrast, in the impaired limb shoulder, flexion torque was observed in 7 subjects and shoulder abduction in 3. The delays in refl ex onset and altered torque patterns in the impaired arm may be related to the abnormal movement synergies observed following stroke. (C) 1999 John Wi ley & Sons, Inc.