Center-of-pressure based postural sway measures: Reliability and ability to distinguish between age, fear of falling and fall history

•Reliability of 18 CoP based postural sway measures is systematically analyzed.•Their ability to distinguish between age, fear falling and fall history is studied.•Eight CoP measures have acceptable levels of relative and absolute reliability.•Three measures are sensitive to detect age-group difference and fear of falling.•No single measure can detect differences between the non-faller and faller groups.

The purpose of this study was to compare the test-retest reliability of a wide variety of center-of-pressure (CoP) based postural sway measures and their ability to detect the differences between the young and older groups (age comparison), between the older low- and high-fear of falling groups (fear of falling comparison), and between the older non-faller and faller groups (fall history comparison). Forty healthy females (twenty each in both young and older groups) performed three trials of bipedal quiet standing on a force platform, in which eighteen reported CoP based measures were computed from recorded CoP trajectory. Intra-class correlation coefficient (ICC), standard error of measurement (SEM) and %SEM were used to quantify their relative and absolute reliability. Fear of falling and retrospective falls of the older group were recorded using falls efficacy scale-international (FES-I) and the history of falls questionnaire respectively. Experimental results showed that eight measures (RMS distance, RMS distance-AP, mean velocity, mean velocity-AP, mean frequency, mean frequency-AP, phase plane parameter and fractal dimension) had acceptable levels of relative and absolute reliability. Three measures (RMS distance-AP, mean velocity, and phase plane parameter) were sensitive to detect age-group difference and fear of falling under both visual conditions, but no single measure was capable to detect differences between the non-faller and faller groups.Relevance to industryThe results of this research provide useful information on the selection of appropriate center-of-pressure (CoP) based postural sway measures to assess individual's balance ability for preventing the occupational falls.