Aging and the recovery of postural stability from taking a step

- Mathematical model of recovering upright stance from taking a single step.
- Implementation of virtual time-to-contact (VTC) in volitional stepping.
- The preferred stepping strategies of older adults are less effective.
- Older adults were less stable after taking a step and slower to recover balance.
- The balance recovery in sideways stepping was slower.

The study examined the effect of aging adults (young: 18-26 years vs. old: 66-73 years) on the recovery of postural stability from taking a single volitional step that varied in direction (forward, backward, sideways) onto force platforms. The recovery of postural stability (as indexed by an exponential decay function) was determined from the dynamic stability of the motions of the center of pressure (COP), center of mass (COM) and virtual time to contact (VTC). The findings showed that in all step directions the older adults required more time to securely perform the step and were less stable after the second foot contact with the surface of support. The decay rate of the recovery of the COP, COM and VTC stable dynamics was reduced and the minimum of VTC lower in the old in contrast to the young adults. The findings reveal that even in taking a single step with preferred spatial-temporal dynamics older adults are slower and less stable in recovery of stance through more closely challenging the limits of the postural stability boundary and its associated potential of a fall.