Selection of entropy-measure parameters for force plate-based human balance evaluation Academic Article in Scopus uri icon

abstract

  • © Springer Nature Singapore Pte Ltd. 2019.Human balance is commonly evaluated through the center of pressure (COP) displacement measured with a force plate, producing 2D time-series that represent COP trajectories in the anteroposterior and mediolateral directions. Entropy measures have been previously used to quantify the regularity of those time-series in different groups and/or experimental conditions. However, these measures are computed using multiple input parameters, the selection of which has been scarcely investigated within this context. This study aimed to investigate the behavior of COP time-series entropy measures using different parameters values, in order to inform their selection. Specifically, we investigated Approximate Entropy (ApEn) and Sample Entropy (SampEn), which are very sensitive to their input parameters: m (embedding dimension), r (tolerance) and N (length of data). A dataset containing COP time-series for 159 subjects with no physical disabilities was used. As a case study, subjects were grouped in young adults (age < 60, n = 85), and older adults (age ¿ 60) with (n = 18) and without (n = 56) history of falls. ApEn and SampEn were computed for m = {2, 3} and r = {0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5} with a fixed data length (N = 1200 points). ApEn and SampEn values were compared between groups using one-way ANOVA. Our results suggest that ApEn and SampEn are able to discriminate with ease between young and older adults for a wide range of m and r values. However, the selection becomes critical for the discrimination between non-fallers and fallers. An m = 2 and r = {0.4, 0.45} are suggested in this case.

publication date

  • January 1, 2018