Clinique romande de réadaptation SUVACare, Sion, Switzerland.
IRR, Institute for Research in Rehabilitation, Sion, Switzerland; Clinique romande de réadaptation SUVACare, Sion, Switzerland.
J Biomech. 2014 Jan 3;47(1):74-80. doi: 10.1016/j.jbiomech.2013.10.011. Epub 2013 Oct 18.
Repetitive falls degrade the quality of life of elderly people and of patients suffering of various neurological disorders. In order to prevent falls while walking, one should rely on relevant early indicators of impaired dynamic balance. The local dynamic stability (LDS) represents the sensitivity of gait to small perturbations: divergence exponents (maximal Lyapunov exponents) assess how fast a dynamical system diverges from neighbor points. Although numerous findings attest the validity of LDS as a fall risk index, reliability results are still sparse. The present study explores the intrasession and intersession repeatability of gait LDS using intraclass correlation coefficients (ICC) and standard error of measurement (SEM). Ninety-five healthy individuals performed 5 min treadmill walking in two sessions separated by 9 days. Trunk acceleration was measured with a 3D accelerometer. Three time scales were used to estimate LDS: over 4-10 strides (λ4-10), over one stride (λ1) and over one step (λ0.5). The intrasession repeatability was assessed from three repetitions of either 35 strides or 70 strides taken within the 5 min tests. The intersession repeatability compared the two sessions, which totalized 210 strides. The intrasession ICCs (70-strides estimates/35-strides estimates) were 0.52/0.18 for λ4-10 and 0.84/0.77 for λ1 and λ0.5. The intersession ICCs were around 0.60. The SEM results revealed that λ0.5 measured in medio-lateral direction exhibited the best reliability, sufficient to detect moderate changes at individual level (20%). However, due to the low intersession repeatability, one should average several measurements taken on different days in order to better approximate the true LDS.
重复性跌倒会降低老年人和患有各种神经障碍患者的生活质量。为了防止行走时跌倒，人们应该依靠与动态平衡受损相关的早期指标。局部动态稳定性 (LDS) 代表步态对小干扰的敏感性：散度指数（最大 Lyapunov 指数）评估一个动力系统从相邻点发散的速度。尽管大量研究结果证明 LDS 作为跌倒风险指数的有效性，但可靠性结果仍然很少。本研究使用组内相关系数 (ICC) 和测量标准误差 (SEM) 来探索步态 LDS 的日内和间日可重复性。95 名健康个体在 9 天的间隔内进行了两次 5 分钟的跑步机行走。使用 3D 加速度计测量躯干加速度。使用三个时间尺度来估计 LDS：跨越 4-10 步 (λ4-10)、跨越一步 (λ1) 和跨越半个步 (λ0.5)。日内重复性通过在 5 分钟测试内进行的三个重复的 35 步或 70 步来评估。间日重复性比较了两次测试，总共有 210 步。日内 ICC（70 步估计/35 步估计）分别为 λ4-10 的 0.52/0.18 和 λ1 和 λ0.5 的 0.84/0.77。间日 ICC 约为 0.60。SEM 结果表明，在左右方向上测量的 λ0.5 具有最佳的可靠性，足以检测个体水平的中度变化（20%）。然而，由于间日可重复性低，应该在不同天进行多次测量，以便更好地近似真实的 LDS。
