Angle of elbow elevation depends on the reach target coordinates

To generate a naturally looking arm movement when using cortically derived hand trajectory is investigated. One approach to solving this task is through the utilization of the elbow swivel angle, based on the assumption that its value changes insignificantly with relation to different target locations. The goal of this study is to test experimentally whether the swivel angle significantly depends on the horizontal and vertical coordinates of the target in case of an unrestraint voluntary reaching movements in 3D. In our experiment, the subjects were required to move their hand to different targets located on a vertical board in front of the subject. The results show that the swivel angle depends systematically on both vertical and horizontal coordinates of the target location. The average range of swivel angle variation is approximately 25 degrees. Thus, the assumption that the swivel angle is approximately the same for different target locations is inadequate. Different methods for determining the exact angular configuration of the arm (e.g. those based on the optimization approach) should be employed.