Department of Physical Performance, Norwegian School of Sport Sciences, Sognsveien 220, 0806 Oslo, Norway.
Center for Research in Human Movement Variability, Department of Biomechanics, University of Nebraska Omaha, Omaha, NE, USA.
J Biomech. 2020 Jul 17;108:109893. doi: 10.1016/j.jbiomech.2020.109893. Epub 2020 Jun 13.
Entropic half-life (ENT½) and statistical persistence decay (SPD) was recently introduced as measures of time dependency in stride time intervals during walking. The present study investigated the effect of data length on ENT½ and SPD and additionally applied these measures to stride length and stride speed intervals. First, stride times were collected from subjects during one hour of treadmill walking. ENT½ and SPD were calculated from a range of stride numbers between 250 and 2500. Secondly, stride times, stride lengths and stride speeds were collected from subjects during 16 min of treadmill walking. ENT½ and SPD were calculated from the stride times, stride lengths and stride speeds. The ENT½ values reached a plateau between 1000 and 2500 strides whereas the SPD increased linearly with the number of included strides. This suggests that ENT½ can be compared if 1000 strides or more are included, but only SPD obtained from same number of strides should be compared. The ENT½ and SPD of the stride times were significantly longer compared to that of the stride lengths and stride speeds. This indicates that the time dependency is greater in the motor control of stride time compared to that of stride lengths and stride speeds.
熵半衰期 (ENT½) 和统计持久性衰减 (SPD) 最近被引入作为行走时步幅时间间隔中时间依赖性的度量。本研究探讨了数据长度对 ENT½ 和 SPD 的影响，并将这些度量应用于步幅长度和步幅速度间隔。首先，从受试者在跑步机上行走一小时的过程中收集步幅时间。ENT½ 和 SPD 是从 250 到 2500 个步幅数计算得出的。其次，从受试者在跑步机上行走 16 分钟的过程中收集步幅时间、步幅长度和步幅速度。从步幅时间、步幅长度和步幅速度计算 ENT½ 和 SPD。ENT½ 值在 1000 到 2500 步之间达到平台，而 SPD 则随包含的步数线性增加。这表明如果包含 1000 步或更多步，则可以比较 ENT½，但应比较相同数量的步获得的 SPD。与步幅长度和步幅速度相比，步幅时间的 ENT½ 和 SPD 明显更长。这表明在步幅时间的运动控制中，时间依赖性大于步幅长度和步幅速度。
