Local dynamic stability of treadmill walking: Intrasession and week-to-week repeatability

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• 作者：Fabienne Reynard ; Philippe Terrier
• 关键词：Gait variability ; Intraclass Correlation Coefficient (ICC) ; Nonlinear dynamics ; Maximal Lyapunov exponent
• 刊名：Journal of Biomechanics
• 出版年：3 January, 2014
• 年：2014
• 卷：47
• 期：1
• 页码：74-80
• 全文大小：414 K

文摘

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 (位_4-10), over one stride (位₁) and over one step (位_0.5). 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 位_4-10 and 0.84/0.77 for 位₁ and 位_0.5. The intersession ICCs were around 0.60. The SEM results revealed that 位_0.5 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.