Aging and time-to-postural stability following a visual perturbation

Background and aims: Postural stability is essential to the performance of most daily activities and is necessary to lead an independent lifestyle. Most functional assessments of balance have only evaluated spatial properties of posture, however, assessments should also evaluate balance in the temporal domain. Both domains provide crucial information to an individual's postural stability. The following study examines time to regain stability and the magnitude of postural motion following a virtual perturbation. Methods: To examine the temporal limitations imposed by age (n=45), 3 adult age groups were tested, young (18-19 yr), young old (60-69 yr), and old adults (70-79 yr). Participants were placed into a virtual room appearing as if the visual surround moved in a discrete antero-posterior motion. A force platform was used to assess postural motion across 4 visual perturbation conditions, 9 and 18 cm and 0.3 and 0.6 Hz. Results: Young adults exhibited significantly less postural motion than both of the older age groups and required the least amount of time to regain postural stability following the discrete visual perturbation, while the old adults required the greatest amount of time. Conclusions: These findings indicate that even small visual perturbations induce strong temporal limitations which are magnified by advancing age. Furthermore, the postural saturation (reduction in postural motion) that is typically found in young adults with increasing movement magnitude was not found in either of the older adult groups. Older adults are at a higher risk of losing balance during this period of time to reacquire postural stability which appears to be unaffected by elevated visual motion.