Effect of a cognitive task during obstacle crossing in hemiparetic stroke patients.

Stroke patients are at a higher risk of falling than the community-dwelling elderly, and many falls are due to contact with an obstacle. This study compared the effects of the simultaneous addition of a cognitive task during obstacle crossing between stroke patients and community-dwelling older adults (control subjects). Participants comprised 20 stroke patients who could walk with or without supervision and 20 control subjects matched for age and height with the stroke patients. Participants were asked to cross a 4-cm-high obstacle while walking at a self-selected speed. The number of failures and the spatial and temporal parameters were compared between a single-task condition (i.e., crossing task only) and a dual-task condition (i.e., verbal fluency task: listing vegetables or animals). Under the dual-task condition, six stroke patients (30%) and three community-dwelling elderly individuals (15%) failed to complete the motor task. Task failure was only due to heel-obstacle contact after toe clearance. In both groups, obstacle-heel distance after clearance was reduced, and the time from heel contact to toe clearance and stride time were significantly increased under dual-task condition versus single-task condition. In addition, group-task interaction for the time from heel contact to toe clearance of the obstacle was significant; this increase in time was significantly greater under dual-task condition in stroke patients than in control subjects. Obstacle crossing in stroke patients involved an increase in crossing performance time and a risk of heel-obstacle contact after crossing. These tendencies appeared stronger under the dual-task condition.