Linear and nonlinear analysis of postural control in frailty syndrome

Abstract

HighlightsFrailty can compromise the integration of postural control systems.This impairment becomes evident after sitting and rising from a chair.The impairment occurs in the frontal and sagittal planes in frail elderly people.

Revised Stability Scales of the Postural Stability Index for Human Daily Activities

“…Entropy-based analysis has been widely applied to different fields, like medicine and biology because of its suitability in analyzing nonlinear data [ 7 , 8 , 10 , 11 , 12 ]. Multiscale entropy (MSE) was introduced to quantify the complexity of limited length time-series data [ 22 ].…”

“…Past studies used various approaches to measure human postural stability evaluation, such as the center of pressure (COP) [ 5 , 6 , 7 , 8 , 9 ], entropy-based methods [ 7 , 8 , 10 , 11 , 12 ], and the Star Excursion Balance Test [ 13 ]. The COP measurement using a force platform is the most commonly used method to evaluate postural stability.…”

“…The COP stabilogram metrics often used to determine the postural stability are mean displacement velocity, total excursion, sway area, and root mean square [ 7 , 8 , 9 ]. Compared to the COP stabilogram metrics, entropy-based methods such as approximate entropy [ 5 ], sample entropy [ 8 ], and multiscale entropy [ 7 , 10 , 11 , 12 ] could better describe the COP data since human physiological is nonlinear and nonstationary [ 10 ]. Despite its validity in detecting the instability in human postural control, the force platform is expensive, cumbersome, and impractical for human daily activity evaluation.…”

Selection of Entropy-Measure Parameters for Force Plate-Based Human Balance Evaluation

“…including every 5 th point of the original time-series in their computation). This procedure has been applied in previous studies in order to reduce redundancy while preserving essential information [6,7,11,13]. Subsequently, Approximate Entropy (ApEn) and Sample Entropy (SampEn) were computed for each COP time-series using all possible combinations of m={2, 3} and r={0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5}.…”

“…More recently, nonlinear measures such as Approximate Entropy (ApEn) and Sample Entropy (SampEn) have been used to quantify the regularity or predictability within COP time-series in different groups or testing conditions [6][7][8][9][10][11][12][13]. Broadly speaking, ApEn and SampEn measure the likelihood that subseries of length m (from a timeseries of length N) that are similar within a tolerance range given by ±r times the standard deviation of the time-series, remain similar for subseries of length m+1.…”