SCALING OF JOINT TORQUE DURING PLANAR ARM MOVEMENTS

The present study scrutinized the ''Motor Program'' concept for aimed arm movements. Human subjects pointed at visual targets in a horizonta l plane, with movements of varying starting positions, amplitudes and directions. We recorded movement kinematics and subsequently calculate d the shoulder and elbow joint torque profiles. Our results indicate t hat the shape of torque profiles is rather uniform across movements an d joints. We defined the size of those profiles by six ''landmark vari ables'', which could be subsequently reduced to three factors using fa ctor analysis: one factor represented torque magnitude and two represe nted different aspects of torque timing. Additional analyses indicated that total torque duration is an important controlled signal. Our fin dings conform with the view that movements are executed by playing bac k scaled versions of prototypical joint torque profiles.