Journals of Gerontology Series A: Biological Sciences and Medical Sciences, Vol 53, Issue 1 B71-B78, Copyright © 1998 by The Gerontological Society of America
Aging and time to instability in posture
SM Slobounov, SA Moss, ES Slobounova and KM Newell
Department of Kinesiology, Pennsylvania State University, University Park, USA.
Two experiments are reported that were set up to examine the spatial-
temporal boundaries of postural instability in upright stance as a function
of age (60-96 years) and postural conditions. Subjects stood on a force
platform under different experimental conditions (vision/no vision and arms
up/down) so that the effect of age on key dynamic properties of postural
stability could be determined. The findings showed that the ratio of the
area of the motion of the center of pressure to the area within the
stability boundary increased with age. Also, the virtual time-to-contact
with the postural stability boundary decreased with age. Collectively, the
findings show that the margins to the spatial-temporal boundaries of
postural stability decrease with advancing age in the elderly. These
reduced margins of dynamic stability may be a factor contributing to the
progressive instability of posture with aging in the elderly.
