Assessment of balance in unsupported standing with elderly inpatients by force plate and accelerometers

Background and aims: Unsupported standing is one of the most important functional tasks involving balance control. Unlike younger people, who have been shown to counteract imbalance preferably with an ankle strategy, older people tend to do so with a hip strategy. These strategies can be described by matching balance measures at floor and hip level, a good match representing an ankle-dominant strategy and a low one a hip-dominant strategy. The aim of this study was to show possible change in the association between force platform measurement at floor level and accelerometry at hip level in elderly inpatients standing unsupported during rehabilitation. Methods: Fortyfour elderly inpatients (mean age 82.5 yrs) after hip fracture or stroke were recruited for the study. Balance was assessed after admission and 2 weeks later on a force platform at floor level and simultaneously by a tri-axial accelerometer at hip level. Results: The correlation between the 2 measures was initially poor to fair (r=0.04 to r=0.51), but increased after 2 weeks of rehabilitation (r=0.30 to r=0.66). Conclusions: A change in the association between measures obtained at lower back level and floor level may indicate a change from a hip- to an ankle-dominant strategy, to counteract imbalance during unsupported standing.