Associations between physical function, balance confidence, and the probability of walking instability among older...

There is a critical need to better understand the physical and psychophysiological factors that precipitate walking instability in older adults. A recent advancement in the capacity to measure walking-related instability from 3D motion analysis - termed "probability of instability" or PoI - holds promise to more accurately capture a person's risk of losing balance.

No study to date has correlated PoI with physical performance (i.e., walking speed or lower extremity strength) or perceptual questionnaires of falls risk (i.e., fear of falling, self-efficacy/balance confidence). Our purpose was to address these gaps in our understanding.

Twenty-eight community-dwelling older adults (age: 73.0 + 5.9 years) walked at their preferred speed with and without optical flow perturbations designed to elicit lateral instability. Motion capture data were used to calculate anterior-posterior (AP) and mediolateral (ML) margins of stability (MoS). The means and standard deviations of MoS were used to develop probability density functions of MoS, from which we determined the probability that MoS< 0 for any given step (i.e., PoI).

We found extensive examples for which mean MoS correlated with physical function and/or self-reported fear and balance confidence. However, many of these significant correlations may be incomplete, as lesser PoI correlated only with slower preferred walking speed and not with lesser self-reported fear of falling or greater balance confidence.

Our findings suggest that: (1) correlations between mean MoS values during walking and psychophysiological outcomes may be incomplete, and (2) older adults may opt to walk slower to compensate for higher probabilities of instability.