Effect of robot-assisted and unassisted exercise on functional reaching in chronic hemiparesis

A common therapeutic approach for the rehabilitation of patients with hemiparesis involves repetitive voluntary movements with manual assistance from a therapist ("active-assist therapy"). We used a novel robotic device to deliver a controlled form of active-assist therapy in chronic stroke patients (N=7). To examine the utility of direct mechanical assistance in rehabilitation of voluntary arm movements, a matched group of subjects with chronic hemiparesis (N=7) performed the same repetitive exercises without the aid of the robotic device. Each group performed 24 therapy sessions over 8 weeks. We found that both groups demonstrated significant improvements in straightness of voluntary reaching movements, with limited improvements in range. Only the group that received robotic therapy significantly improved the smoothness of reaching. Improvements in both groups transferred to an unpracticed reaching movement and the timed performance of functional tasks. There were no significant differences in the magnitude of improvements between the two groups. These results suggest that it is the action of repetitively attempting to move, rather than the mechanical assistance provided by the robot, that stimulates arm movement recovery. However, imposing a smooth trajectory during practice of the reaching movements may help subjects learn how to produce smoother movements. In addition, practicing robot-assisted or unassisted reaching movements apparently improves control processes that generalize to other functional movements.