Abstract
Aging causes foot arches to collapse, possibly leading to foot deformities and falls. This paper proposes a set of measures involving an entropy-based method used for two groups of young adults with dissimilar foot arches to explore and quantize postural stability on a force plate in an upright position. Fifty-four healthy young adults aged 18–30 years participated in this study. These were categorized into two groups: normal (37 participants) and flatfooted (17 participants). We collected the center of pressure (COP) displacement trajectories of participants during upright standing, on a force plate, in a static position, with eyes open (EO), or eyes closed (EC). These nonstationary time-series signals were quantized using entropy-based measures and traditional measures used to assess postural stability, and the results obtained from these measures were compared. The appropriate combinations of entropy-based measures revealed that, with respect to postural stability, the two groups differed significantly (p < 0.05) under both EO and EC conditions. The traditional commonly-used COP-based measures only revealed differences under EO conditions. Entropy-based measures are thus suitable for examining differences in postural stability for flatfooted people, and may be used by clinicians after further refinement.
Highlights
Feet can be used as an indicator of the human aging process
We found that: (1) based on traditional raw-data-based measures from center of pressure (COP) signals, Mean resultant distance (MDIST) and root mean square distance (RDIST) exhibited significant differences in the ML direction with eyes open (EO) (Table 2); (2) the complexity index (CI) values exhibited significant differences in the AP direction with eyes closed (EC) in the low-frequency
IMF6 and IMF7 signals (Table 3); (3) there were no significant differences in the multivariate MSE (MMSE) (Table 5); and
Summary
Feet can be used as an indicator of the human aging process. Reduced walking and exercise and increasing body weight can lead to retardation of the foot muscles and to foot deformities and falls, as well as increasingly flatfooted structures [1,2,3]. For people with abnormal flat-footed structures, the ability to absorb shock and to maintain postural stability is reduced This may result in inflammation of the plantar fascia, plantar lesions, and body pain, and may even lead to an increased risk of falling [4,5,6,7]. In this way, the structure of the foot arch is important for posture [8], and may be an important variable to assess during pre-participation physical examinations [3,9]. Clinicians need to consider further evidence when selecting management options for flat feet
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