Recurrence Quantification Analysis of Age-Related Changes in Postural Fluctuations During Quiet Standing on a Slope

Age-related degeneration of posture stability would be a leading factor to falls in elderly adults. The purpose of our research was to explore the aging effects on fluctuations in posture when subjects stand quietly on slopes. Eighteen healthy elderly subjects and 18 gender-matched young subjects were recruited. They were required to stand quietly at -10°, -5°, 0°, 5° and 10° inclinations with visual feedback. The center of pressure (COP) signals of feet were recorded simultaneously by a force platform. Recurrence quantification analysis (RQA) was used as an analytical tool for the COP data. Determinism (DET) and entropy (ENT) derived from RQA were assessed. No significant differences between groups were found but the maximum differences of the values were found when subjects stood on -5° slope. The elderly showed higher values of DET and ENT compared with the young. Besides, the DET and ENT of elderly group in AP direction showed a higher value when subjects stood on a flat in comparison with the values on the inclination. This finding sheds light on the effects of age-related posture control during standing. The elderly group, compared with young group, stand quietly with reduced behavioral flexibility and decreased adaptability. The methodology developed in this study may facilitate the assessment of falling risk in elderly population. In the future study, slope could be a better choice to detect the ability of balance and study postural control mechanisms.