Cambridge Centre for Sport and Exercise Sciences, Anglia Ruskin University, East Road, Cambridge, UK.
Hum Mov Sci. 2021 Apr;76:102768. doi: 10.1016/j.humov.2021.102768. Epub 2021 Feb 5.
The aim of this study is to evaluate how speed affects non-linear measures of variability. Fixed and self-selected speeds were compared to an anatomically scaled speed calculated based on leg length to evaluate which provided a more reproducible result between subjects.
Sixteen subjects ran on a treadmill at a fixed, scaled and self-selected speed and at ±10% in each case. Kinematic data were collected for two minutes at 250 Hz for each trial. Sample entropy (SaEn) and maximum Lyapunov exponents (LyE) were calculated from the sagittal knee and hip joint angles to evaluate regularity of gait and local stability. These nonlinear measures were compared to evaluate the dynamic similarity of the movement in each case, and to evaluate speed as a confounding variable in non-linear analysis.
An anatomically scaled speed shows more dynamic similarity than a fixed or self-selected speed with the lowest observed coefficient of variation for each measure. This was found to be statistically significant for both nonlinear measures of the hip (SaEn p = 0.038; LyE p = 0.040). Speed was not found to be a confounding variable in non-linear analysis of running gait of a healthy population (η < 0.05).
Changes in speed by ±10% do not significantly affect stability and variability of gait for healthy participants, suggesting that they make adaptations to ensure optimal gait variability. Anatomically scaled speeds provide a more reliable methodology for both linear and non-linear analysis by providing a definitive protocol, suggesting it could replace self-selected or fixed speeds in future research.
本研究旨在评估速度如何影响非线性变异性测量。将固定速度、自定速度与基于腿长的解剖比例速度进行比较，以评估哪种速度在受试者之间能提供更可重复的结果。
16 名受试者在跑步机上以固定速度、比例速度和自定速度以及每种速度的±10%速度进行跑步。在每次试验中，以 250 Hz 的频率采集两分钟的运动学数据。从矢状面膝关节和髋关节角度计算样本熵（SaEn）和最大 Lyapunov 指数（LyE），以评估步态的规律性和局部稳定性。比较这些非线性测量值，以评估每种情况下运动的动态相似性，并评估速度作为非线性分析中的混杂变量。
与固定或自定速度相比，解剖比例速度显示出更高的动态相似性，每个测量值的观察变异系数最低。这在髋关节的两个非线性测量值中均具有统计学意义（SaEn，p=0.038；LyE，p=0.040）。对于健康人群的跑步步态的非线性分析，速度并不是一个混杂变量（η<0.05）。
速度变化±10%不会显著影响健康参与者步态的稳定性和变异性，这表明他们会进行适应性调整以确保最佳的步态变异性。解剖比例速度为线性和非线性分析提供了更可靠的方法，因为它提供了明确的方案，这表明它可以在未来的研究中替代自定或固定速度。
