Balance control and weight bearing asymmetry under different levels of cognitive demands in stroke patients

Introduction: Balance control impairment and weight bearing asymmetry (WBA) are the most common complications in stroke patients. Interactions between sensory-motor and cognitive systems are necessary for balance control. Cognitive task can affect the balance control and weight bearing asymmetry in these patients. The purpose of this study was to investigate the effect of cognitive task and its difficulty on balance control and weight bearing asymmetry in chronic stroke patients. Materials and Methods: Twenty-two patients with chronic stroke (30.7&plusmn;42.2 month post-stroke) and 23 healthy individuals participated in the study. All the patients could stand independently and had weight bearing asymmetry towards the nonparetic leg. We used two force plates to collect balance related data including Area, Amplitude, velocity of cop displacement in ML and AP planes in standing position. In addition, simple and difficult stroop (color-word) tasks were used as cognitive tasks. All the participants underwent 5 test conditions including standing, sitting and simple cognitive, sitting and difficult cognitive, standing and simple cognitive, and standing and difficult cognitive tasks. Results: Interaction effect of group in cognitive task was not significant for any of COP parameters and WBA. Also no significant difference was seen between COP parameters and WBA for simple and difficult dual tasks. Main effects of group and cognitive task were significant for WBA, standard deviation of center of pressure sway amplitude and sway velocity (p< 0.05), showing increasing pattern from patient to healthy group and from single to dual task. Conclusion: Results showed that stroop task is challenging enough that cognitive demand arising from it both in simple and difficult levels, by the same amount deteriorates upright balance and increases WBA in stroke patients