Experimental assessment of a coincident timing motor task of the arm under a passive mechanical perturbation

There are many motor control aspects that must be taken into account for the design and application of rehabilitation robots and exoskeletons. In this respect the outcomes from behavioral motor control studies can provide relevant design criteria. In this context, to verify the level of motor learning and adaptation under the influence of mechanical perturbations, we used a coincident timing task. The task consisted of hitting with the hand a virtual target falling on the screen. The movement was performed in the horizontal plane and consisted of an elbow flexion to reach the real marker on a table. Sixteen volunteers were divided into two groups: 1-task without perturbation on the hand and, 2-task with a predictable mechanical perturbation on the hand. Data were analyzed by the percentage of correct responses and the tendency of the correct responses. In order to assess the duration as well as the velocity and acceleration of the movement, inertial sensors were used. The results showed a task performance improvement for group 2 when compared to group 1. Furthermore, group 1 showed a trend to delay on correct responses, while the trend in group 2 was to anticipate on correct responses. These results indicate that a predictable mechanical perturbation during learning this coincident timing task can improve the motor learning process and paves the way to further experiments with the use of an upper limb exoskeleton.