Automatic and voluntary lateral weight shifts in rehabilitation of hemiparetic patients

One of the main objectives of exercise therapy for hemiparetic patients is the rehabilitation of their impaired ability to accept and bear bodyweight on the involved lower extremity. The purpose of this study was to compare two types of therapeutic exercises, automatic and voluntary weight shifts, used as treatment for this problem. Thirteen hemiparetic patients and nine age-matched healthy controls participated in the study. Criterion variables were four: (1) body sway; (2) location of the centre of pressure; (3) activation pattern of the gluteus medius and medial gastrocnemius muscles; and (4) magnitude of activation of these two muscles. Each subject was tested three times: (1) during static stance; (2) while standing on a moving platform that imposed automatic lateral weight shifts; and (3) while standing on a stationary base and voluntarily shifting bodyweight from one lower limb to the other. Values of sway and location of the centre of pressure on the mediolateral axis were collected by the Chattecx balance system; magnitude and modulation of the muscular activity in both lower extremities were recorded with surface electromyography. The findings showed significant differences between patients and controls in all four variables. Regarding differences between exercise modes, the main finding pointed to larger sways in voluntary as compared to automatic weight shifts. Presumably, body fixation during automatic perturbations was manifested in a decreased body sway. Stance symmetry and the EMG activation profile of the paretic muscles were not improved by either exercise mode.