The influence of lateral stabilization on walking performance and balance control in healthy and post-stroke individuals

Stroke survivors often have diminished balance control and are highly prone to falling, which can lead to long-term injuries, disabilities and reduced quality of life. Maintaining balance during gait requires active control, but this control may be impaired post-stroke. Individuals post-stroke often walk with wider steps when compared to healthy, age-matched controls, which can negatively affect balance control. Previous studies have shown when lateral stabilization is applied to the pelvis, healthy young and older adults walk with reduced step width, step width variability and energetic cost, suggesting that lateral stabilization reduces the need for active frontal plane balance control. The purpose of this study was to determine if lateral stabilization is effective at improving gait performance and dynamic balance in healthy (Controls) and post-stoke (Responders) individuals (i.e., those who responded to the stabilization by reducing their step width). Controls and Responders significantly reduced their step width and mediolateral pelvis sway while stabilized, but these changes did not lead to improved gait performance (e.g., foot placement and propulsion symmetry) or balance control. There were no significant and clinically relevant changes in either group’s gait performance, and in some cases the Responders’ gait performance decreased when stabilized. Both groups exhibited decreased balance control that resulted in an increased range of frontal plane whole body angular momentum (H). This increase was the result of increased relative velocity between the pelvis and the head, arms and trunk (HAT) segment. The increase in relative motion may indicate that stabilizing the pelvis does not improve balance control unless care is taken to make sure that the relative motion between the pelvis and HAT segment does not increase as a result. The results of this study suggest that reduction in absolute motion of the pelvis, as opposed to relative motion between the pelvis and upper body, may lead to decreased balance control by increasing the range of frontal plane H. This finding has important implications for locomotor therapies that seek to improve balance control by stabilizing the pelvis.