Ahmadi Samira, Sepehri Nariman, Wu Christine, Szturm Tony
Department of Mechanical Engineering, University of Manitoba, Winnipeg, MB R3T 5V6, Canada.
Department of Physical Therapy, College of Rehabilitation Sciences, University of Manitoba, Winnipeg, MB R3E 0T6, Canada.
Entropy (Basel). 2018 Aug 6;20(8):579. doi: 10.3390/e20080579.
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 (), tolerance size (), 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.
样本熵（SampEn）已被用于量化人类步态信号的规律性或可预测性。有研究探讨了该测量方法在步幅间时空步态变量上的适当应用。然而，当应用于“完整”步态信号时，该测量方法对信号预处理以及模板大小（）、容差大小（）和采样率的变化值的敏感性尚未得到研究。完整步态信号是从力传感器或惯性传感器获得的整个时间序列数据。本研究系统地研究了内侧-外侧方向压力中心位移（ML COP-D）的样本熵对参数值变化和两种预处理方法的敏感性。这两种方法分别是过滤高频成分以及对信号进行重采样，以使每步的数据点平均数量相同。通过比较仅跑步机行走（WO）和双任务（DT）条件下的样本熵，研究其判别能力。结果表明，样本熵在不同参数值下保持了两种行走条件之间的方向差异，从WO到DT条件下显著增加，特别是当信号进行低通滤波时。此外，当测试条件下的步态速度不同时，信号应进行低通滤波和重采样，以使每步的数据点平均数量相同。
