Motor Control Laboratory, Department of Biomedical Kinesiology, Research Centre for Movement Control and Neuroplasticity, K.U. Leuven, Belgium.
J R Soc Interface. 2013 Mar 20;10(83):20120999. doi: 10.1098/rsif.2012.0999. Print 2013 Jun 6.
Falling poses a major threat to the steadily growing population of the elderly in modern-day society. A major challenge in the prevention of falls is the identification of individuals who are at risk of falling owing to an unstable gait. At present, several methods are available for estimating gait stability, each with its own advantages and disadvantages. In this paper, we review the currently available measures: the maximum Lyapunov exponent (λS and λL), the maximum Floquet multiplier, variability measures, long-range correlations, extrapolated centre of mass, stabilizing and destabilizing forces, foot placement estimator, gait sensitivity norm and maximum allowable perturbation. We explain what these measures represent and how they are calculated, and we assess their validity, divided up into construct validity, predictive validity in simple models, convergent validity in experimental studies, and predictive validity in observational studies. We conclude that (i) the validity of variability measures and λS is best supported across all levels, (ii) the maximum Floquet multiplier and λL have good construct validity, but negative predictive validity in models, negative convergent validity and (for λL) negative predictive validity in observational studies, (iii) long-range correlations lack construct validity and predictive validity in models and have negative convergent validity, and (iv) measures derived from perturbation experiments have good construct validity, but data are lacking on convergent validity in experimental studies and predictive validity in observational studies. In closing, directions for future research on dynamic gait stability are discussed.
跌倒对现代社会中稳步增长的老年人口构成了重大威胁。预防跌倒的主要挑战是识别因步态不稳定而有跌倒风险的个体。目前，有几种方法可用于估计步态稳定性，每种方法都有其优点和缺点。在本文中，我们回顾了现有的测量方法：最大 Lyapunov 指数（λS 和 λL）、最大 Floquet 乘子、变异性测量、长程相关性、外推质心、稳定和不稳定力、足部放置估计器、步态敏感规范和最大允许扰动。我们解释了这些措施代表什么以及如何计算它们，并评估了它们的有效性，分为构建有效性、简单模型中的预测有效性、实验研究中的收敛有效性和观察性研究中的预测有效性。我们的结论是：（i）变异性测量和 λS 的有效性在所有级别都得到了最佳支持，（ii）最大 Floquet 乘子和 λL 具有良好的构建有效性，但在模型中的阴性预测有效性、阴性收敛有效性和（对于 λL）观察性研究中的阴性预测有效性，（iii）长程相关性缺乏构建有效性和模型中的预测有效性，且具有阴性收敛有效性，以及（iv）来自扰动实验的测量具有良好的构建有效性，但在实验研究中的收敛有效性和观察性研究中的预测有效性方面的数据缺乏。最后，讨论了动态步态稳定性未来研究的方向。
