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Summary Objectives Postural stability is showed to decline with age and to be particularly challenging for older people during multitasking activities. However, the effect of different levels of physical fitness on postural stability performances during multitasking remains unclear. This cross-sectional study aimed to investigate the impact of dual-task (DT) and triple-task (TT) performances on postural stability among older adults with a different level of physical fitness (i.e., master cyclists and physically active), and to compare them with healthy untrained older and young adults. Equipment and methods Seven master cyclists (mean age 70 ± 3 years), 7 physically active older adults (mean age 73 ± 1 year) 10 untrained older adults (mean age 73 ± 3 years) and 10 untrained young adults (mean age 25 ± 2 years) participated in the study. Data were recorded during: 1) a quiet upright stance task (single-task) and while performing an additional (dual-task), 2) manual, 3) cognitive task or 4) manual and cognitive task concurrently (triple-task). Area and Perimeter described by the center of pressure and mean velocity in anterior-posterior and medio-lateral directions were analyzed. Results Generally, a decrease in postural stability variables (area, perimeter, mean velocity in anterior-posterior and medio-lateral directions) was observed during dual and triple-task in all groups (all P values Conclusion The results underlined that to be a cyclist or to be physically active during aging are beneficial to maintain postural stability during multitasking activity and consequently to decrease the risk of falling observed in aging.

We investigate human postural sway velocity time series by computing two dynamical statistics quantifying the smoothness (the central tendency measure or CTM) and the regularity (the sample entropy or SampEn) of their underlying dynamics. The purpose of the study is to investigate the effect of aging and vision on the selected measures and to explore the nature of postural dynamics by performing surrogate data tests. A group of 14 young subjects was compared to a group of 11 older healthy subjects in two visual conditions: with eyes open (EO) and with eyes closed (EC). The results suggest that vision and age do not influence the two statistics of the velocity data in the same way. More specifically, the smoothness statistic is able to detect the aging effect. The regularity measure is sensitive to the visual feedback removal. In contrast with some findings in the literature, the results of the surrogate data tests indicate that the center of pressure velocity dynamics are stochastic and are not produced by a purely determinisitic behavior. Finally, we discuss some potential implications of our results in terms of postural control mechanisms.

We analyze the irregularity of human postural sway data during quiet standing using the sample entropy (SampEn) algorithm. By considering recent methodological developments, we show that the SampEn parameter is able to characterize the irregularity of the center of pressure fluctuations through the analysis of the velocity variable. We present a practical method to select the input parameters of the SampEn algorithm. We show that the computed SampEn successfully discriminates two sensory conditions (eyes-open and eyes-closed) in a group of healthy young adults. We also perform surrogate data tests to investigate the nature of the underlying dynamics of our experimental data. Finally, the results of the proposed approach are compared to those obtained with the multiscale entropy algorithm.