Can a kinetic optimization criterion predict both arm trajectory and final arm posture?

The following two characteristics have been well demonstrated concerning the features of a point-to-point human arm movement on a plane. (1) The path is a roughly straight line, but is slightly curved. (2) The velocity profile is bell shaped with a single peak. Several models have been proposed to explain these features. Four criteria for trajectory planning based on optimal principles have been proposed. They are the minimum hand jerk criterion, the minimum angle jerk criterion, the minimum torque change criterion, and the minimum commanded torque change criterion. Trajectories generated by the minimum commanded-torque change model have been shown to correspond well with measured trajectories in a horizontal and sagittal work space. However, previous works had been restricted to trajectories on a two-dimensional plane. Trajectories and final arm postures had not been examined in three-dimensional space. In this paper, we quantitatively discuss predictions based on these criteria for human arm trajectories and arm postures in three-dimensional space. Finally, we report that both measured hand trajectories and arm postures were closest to trajectories and postures predicted by the minimum commanded torque change criterion.