The coordination of reaching and grasping in spastic hemiparesis

The coordination of uni- and bimanual reaching and grasping movements in six subjects with spastic hemiparesis was studied. First, the temporal course of the movements and the kinematics of the end effector were assessed. While these are useful assessments, they provide the practitioner little information on the nature of the deficit, or on the principles that may guide movement reorganization. Therefore, we also assessed movement reorganization in these subjects by studying joint involvement, trunk involvement, and joint coupling, the latter operationalized by the cross correlation between excursions of joint angle pairs. Large manual asymmetries existed in unimanual task performance. These were more pronounced for grasping than for reaching, because the impaired hand stayed longer at zero velocity before lifting the object in the grasping task. The results further showed that the unimpaired hand ÎmimickedÌ the impaired hand on a number of kinematic variables under bimanual responding. With respect to movement reorganization, the results showed that the impaired hand attained the movement goal with decreased involvement of the elbow and shoulder joints, increased trunk involvement, and weaker joint coupling. With respect to the latter, a prominent finding was that movements of the impaired limb were segmented. Movements started with a large shoulder involvement and little or no elbow extension, followed by a decrease in shoulder involvement and increase in elbow extension. These findings may exemplify an adaptive movement strategy. To avoid (increased) stretch reflexes that are characteristic of spasticity, movements of the different joints were performed serially, rather than simultaneously. To that aim, joint ranges were limited and task completion was left to the (relatively unaffected) trunk. Given the adaptive character of these phenomena, it is doubtful whether therapy that focuses at restoring the 'normal' movement pattern will be beneficial