Enhancing clinical measures of postural stability with wearable sensors.

About 30% of individuals over the age of 65, and 50% over age 80, fall at least once per year. Fall-related injuries cost the Canadian health care system $2.8 billion annually. Risk for falls in older adults is commonly assessed in the clinical environment using tools such as the Short Physical Performance Battery (SPPB), which include subjective assessments of postural sway while standing under various sensory conditions. This study uses wearable accelerometers and a force plate to quantify measures of postural stability during these tasks. Four participants were asked to maintain quiet stance in six different conditions, while their center of pressure (COP) and accelerations from six accelerometers were recorded. Standard deviations in signals were used as measures of postural sway. The sway observed in all sensors increased with the difficulty of the stance condition. Manipulation of vision and surface stiffness caused greater changes in sway in the AP than ML direction, while changes in stance configuration were more evident in the ML direction. Furthermore, the ankle sensor was the most sensitive in registering changes in sway when manipulating vision and surface stiffness (showing an increase of 236% over baseline values in AP sway with eyes closed and standing on foam), while the thigh was most sensitive to changes in stance width (showing an increase of 336% over baseline values in ML sway in the tandem stance condition). This study contributes in establishing the utility of wearable sensors for quantifying postural stability under various stance configurations in future studies with high-risk older adults.