Evidence for a relationship between abnormal static torque synergies and disturbances of planar arm movements in hemiparetic subjects: preliminary results

The purpose of this study was to explore the relationship between abnormal static torque synergies and disturbances of planar arm movements in stroke subjects (n=3). Abnormal static torque synergies (e.g. coupling between shoulder abduction-external rotation and elbow flexion torques) were identified in the impaired arm of all three subjects using 6 degree of freedom load cell measurements. As a result, the ability of subjects to produce static elbow extension and shoulder abduction torques simultaneously was severely compromised. Based on comparisons of actively and passively supported arm movements, similar manifestations of these abnormal synergies were present under dynamic conditions. Disturbances of actively supported reaching movements (which required shoulder abduction and external rotation torques) were associated with a reduction in the elbow extension torque, relative to the passively supported condition. The scientific and clinical implications of these preliminary findings will be discussed.