Effects of object use on reaching and postural balance: A comparison of patients with unilateral stroke and healthy controls

OBJECTIVE: To evaluate whether the functional use of certain task objects while standing influences reaching performance and postural balance in persons with left or right cerebral vascular accidents, and also in healthy individuals. DESIGN: Thirty-five stroke patients (20 patients with left and 15 patients with right cerebral vascular accidents) and 31 healthy controls (15 using the left and 16 the right arm) performed two experimental reaching tasks (task object present vs. absent) using the less affected arm while standing. For the object-present task, subjects held a glass and moved it forward as far as possible. For the object-absent task, subjects simply reached forward as far as possible. We measured reaching performance using kinematic analysis and assessed postural control using derivatives of the center of pressure, including forward displacement, mediolateral shift, and average velocity. RESULTS: Object presence did not significantly improve overall reaching performance in any group. However, for patients with left cerebral vascular accidents and controls (using either the left or the right arm), there were significant effects of object presence on the average velocity of the center of pressure. For patients with right cerebral vascular accidents, there were significant effects of task object on the forward distance and average velocity of the center of pressure. CONCLUSIONS: The positive findings regarding center-of-pressure derivatives suggest that a functional use of objects during a standing reaching task can decrease postural sway, as represented by the average velocity of the center of pressure, in individuals with and without stroke. Patients with right cerebral vascular accidents may benefit considerably more from functional object use during a standing reaching task, apparently because such tasks can facilitate greater forward displacement of the center of pressure.