Key result
Sample entropy of mediolateral center of pressure displacement showed a significant increase from walk-only to dual-task conditions, especially when signals were low-pass filtered.
When analyzing whole gait signals using Sample Entropy, signals should be low-pass filtered and resampled to have the same average number of data points per stride, especially when gait speed differs between conditions.
SampEn of ML COP displacement maintains condition differences across parameters when low-pass filtered; leaves open standardized protocols for clinical gait analysis.
Sample entropy (SampEn) has been used to quantify the regularity or predictability of human gait signals. There are studies on the appropriate use of this measure for inter-stride spatio-temporal gait variables. However, the sensitivity of this measure to preprocessing of the signal and to variant values of template size (m), tolerance size (r), and sampling rate has not been studied when applied to “whole” gait signals. Whole gait signals are the entire time series data obtained from force or inertial sensors. This study systematically investigates the sensitivity of SampEn of the center of pressure displacement in the mediolateral direction (ML COP-D) to variant parameter values and two pre-processing methods. These two methods are filtering the high-frequency components and resampling the signals to have the same average number of data points per stride. The discriminatory ability of SampEn is studied by comparing treadmill walk only (WO) to dual-task (DT) condition. The results suggest that SampEn maintains the directional difference between two walking conditions across variant parameter values, showing a significant increase from WO to DT condition, especially when signals are low-pass filtered. Moreover, when gait speed is different between test conditions, signals should be low-pass filtered and resampled to have the same average number of data points per stride.
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Ahmadi et al. (2018) studied Human gait. Dual-task (DT) condition vs. Treadmill walk only (WO) was evaluated on Sample entropy (SampEn) of the center of pressure displacement in the mediolateral direction. Sample entropy of mediolateral center of pressure displacement showed a significant increase from walk-only to dual-task conditions, especially when signals were low-pass filtered.