Whole-body and Segmental Contributions to Dynamic Balance in Stair Ambulation are Sensitive to Early-Stage Parkinson's Disease.

Stair ambulation is commonplace in daily living activities, yet biomechanically more challenging compared to level-ground walking. With reduced lower-limb muscle strength and increased rigidity of extremities, people with Parkinson's disease (PD) experience impaired balance and higher incidence of falls each year. However, the regulation of whole-body dynamic balance of individuals with PD in stair walking is unclear. Whole-body angular momentum (H) is a useful metric for assessing dynamic balance that accounts for the angular movements of all body segments about the body center-of-mass (COM). In this study we investigated the regulation of H and segmental contributions to H during stair ascent and descent walking in individuals with PD compared to healthy subjects. During stair descent, the magnitude of sagittal-plane H increased in participants with PD compared to healthy subjects in ipsilateral (most affected side) leg stance. Meanwhile, the legs contributed more to sagittal-plane H in individuals with PD compared to healthy subjects. During stair descent walking, the magnitude of transverse-plane H was also greater in participants with PD compared to healthy subjects during the second half of ipsilateral leg gait cycle. The increased magnitude of negative (i.e., forward) sagittal-plane H in the ipsilateral stance of stair descent walking suggests that individuals with PD experience greater difficulties maintaining their forward rotation during such tasks.