Manipulating perceived postural stability in younger and older adults and the effect on standing postural stability...

Evidence suggests that neuromuscular function and balance of younger adults can be modified by the perception or predictions of an outcome. This study aimed to determine the effect of manipulating perception of postural stability on standing postural stability and gait of younger and older adults. 14 older adults and 14 younger adults completed quiet normal standing (NS) and tandem stance (TS) postural stability, and normal preferred (PWS) and fastest (FWS) walking speed gait assessments under three conditions. Conditions included control (CON) with no manipulation, and stable (STB) and unstable (UNS) conditions where participants were led to believe they were receiving transcranial magnetic stimulation to regions that would increase or decrease postural stability, respectively. Perceived stability decreased following UNS during NS and FWS compared to CON and in TS compared to STB, younger adults also had greater perceived stability than older adults in TS. In NS medio-lateral postural sway was less complex in UNS than CON and STB and anterior-posterior sway complexity was lower in older than younger adults. However, no effects of the manipulation were found in TS. PWS walking speed was greater in CON than STB or UNS, and in FWS the walk ratio was greater in CON than STB or UNS, both indicative of more cautious gait. This study provided novel insight to the effects of manipulating perceived stability on postural stability of younger and older adults. We suggest these changes result from changes to predictive models of stability and associated (un)certainty of predictions pertaining to sensory information.