Characterization of balance control through dynamic posture shifts

The control of posture is achieved by complex integrated visual, vestibular, and somatosensory systems. Neurological disorders such as Parkinson's disease (PD) and aging may affect these systems resulting in compromised balance control and subsequent increase in risk of falling. Typically, balance control is evaluated with static posturography and dynamic posturography involving applied or volitional perturbation. In this study, we have utilized dynamic posture shifts that mimic everyday reaching tasks to distinguish balance performance among young, elderly, and people with PD. A total of 57 subjects were recruited: young (21 subjects, 19-32 years), elderly (22 subjects, 50-75 years), and PD (17 subjects, 53-72 years). The dynamic posture shift task involves subjects moving their Center-of-Pressure (CoP) from a center (quiet standing position) to different outward targets (leaning position) then back to center, and hold their CoP inside the targets for about 2 seconds. During these movements, their CoP was displayed in real-time as a circular cursor on a monitor at eye level. Many balance indices were calculated from stabilogram obtained from CoP data of each target presentation. Of them, the path length during movement phase was significantly different (p