The effects of a short-term memory task on postural control of stroke patients

Background: Many studies have been conducted on the changes in the balance capabilities of stroke patients. However, results regarding the effects of dual-task activities on postural control in these patients have been variable. Objective: To evaluate the effects of a short-term memory task on the sway characteristics of stroke patients. Method: Center of pressure (COP) fluctuations were measured in three levels of postural difficulty (rigid surface with closed and open eyes and foamsurface with closed eyes), aswell as two levels of cognitive difficulty (easy and difficult). COP parameters included mean velocity, standard deviation of velocity in both medial-lateral (M.L) and anterior-posterior (A.P) directions, total phase plane portrait, area. Nineteen stroke patients and 19 gender, age, height, and weight matching healthy volunteers participated in this study. Results:Our findings indicate thatmean velocity (F=14.21, P=0.001), standard deviation of velocity in bothM.L (F=17.50, P50.000) and A.P (F=11.03, P=0.002) directions, total phase plane portrait (F=44.12, P50.001), and area (F=13.95, P=0.01) of center of pressure of patients were statistically greater than normal subjects, while significant interaction of group×postural difficulty and postural×cognitive difficulty were observed for all parameters of postural sway. Conclusions: Different measures of postural sway showed complex response to postural and cognitive difficulties between stroke patients and normals. Cognitive error was not affected by the main effects of group and postural difficulty, while greatly increased at more difficult cognitive task (F=75.73, P=0.000).