Postural sway parameters using a triaxial accelerometer: comparing elderly and young healthy adults

The purpose of this study was to evaluate the sensitivity of 16 parameters derived from acceleration to detect changes caused by age and visual conditions during quiet standing and detect and minimise possible sources of unwanted variability that could affect accelerometer measures on the trunk. Twenty-seven healthy subjects, including 16 elderly (age, 69.3 ± 3.6 years) and 11 young (age, 23.6 ± 2.2 years) subjects, were evaluated. The parameters evaluated include root-mean-square values, fractal dimensions, path length, range, frequency dispersion and power spectrum among others derived from these values. These 16 parameters evaluated for each axis of movement and/or derivations resulted in 59 sub-parameters. These 59 sub-parameters were analysed in the elderly and young groups and under the open-eye and closed-eye conditions. The results showed that 30 sub-parameters detected differences for an age effect with open eyes, 18 detected differences with closed eyes, 25 detected differences for the young group standing with closed-open eyes and 37 detected differences for the elderly with closed and open eyes (p < 0.01). We used simple signal processing for the accelerometry signals to minimise the effects of unwanted variability that could affect the results. The results showed better performance compared with those results published previously using force platforms to evaluate postural sway. The results presented here should be useful for researchers who want to use accelerometry to evaluate steady postural balance.