Characteristics of postural reactions to unexpected loss of balance during standing in stroke survivors with emphasis on arm reactions

Abstract

Falls after stroke are a major health concern, as they are one of the most frequent complications. An important and effective strategy to avoid falling is the “change of support” strategy, which is characterized by rapid compensatory stepping and/or grasping that increase the base of support, and by so, stability is regained. Using the arms may also be an effective way to avoid falling when balance is lost due to balance perturbations. Here we aimed to characterize the arm responses to perturbations in stroke patients. Fifteen post-stroke subjects and 15 age and gender matched healthy controls were exposed to unexpected surface translations while standing on a movable platform (Balance Tutor, MediTouch, Israel). Perturbation intensity increased in six levels of difficulty. Kinematic parameters were collected using the Ariel Performance 3D motion Analysis System (APAS) and the data was analyzed by MatLab algorithms written especially for the study. Post-stroke subjects and healthy controls had a symmetric response with two arms. Stroke group had a few reactions with one arm mostly with the paretic arm. We found a significant difference in the overall arm displacement and overall arm velocity between the right arm of control group and the paretic arm of stroke group. When we compared between the paretic and non-paretic arms of stroke survivors we found that the non-paretic arm had a faster reaction time, larger displacement and the paretic arm has a higher velocity. Arm reaction time was faster than leg reaction time. Our results show that hemiparetic stroke patients have the ability to respond with both arms, similar to healthy control subjects, but stroke survivors’ responses seems to have reflexive and spastic movement patterns, not as effective as the movement patterns observed in healthy controls.