Kinematic variability and local dynamic stability of upper body motions when walking at different speeds
Kinematic variability and local dynamic stability of upper body motions when walking at different speeds
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DOI：
10.1016/j.jbiomech.2004.12.014
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发表时间：
2006-01-01
影响因子：
2.4
通讯作者：
Marin, LC
中科院分区：
文献类型：
--
作者：
Dingwell, JB;Marin, LC
老年人和步态障碍患者的一个普遍特征是他们走得比健康对照组慢。许多临床医生认为，这些患者走得更慢是为了提高他们的稳定性，就像健康人在冰上行走时会放慢速度一样。然而，走得慢也会导致更大的变异性，这通常被认为意味着稳定性下降。如果这是真的，那么放慢速度将与维持稳定的目标完全背道而驰。这项研究试图通过直接量化运动系统对表现为自然运动学可变性的局部扰动的敏感性来解决这一悖论。11名年轻健康的受试者以五种不同的速度在机动跑步机上行走。在连续行走过程中，记录放置在第一胸椎上的单个标记的三维运动。计算每个时间序列的平均步幅-步幅标准差和最大有限时间Lyapunov指数，以分别量化这些动作的变异性和局部动态稳定性。对相依测量与步行速度的二次回归分析显示，所有三个平均标准差都呈高度显著的U型趋势，但对于六个有限时间Lyapunov指数中的五个，具有显著或接近显著的二次项的高度显著的线性趋势。在这五项测量中，受试者在较慢的速度下表现出一致的更好的局部动态稳定性。这些结果支持了基于临床的直觉，即跌倒风险增加的人走得更慢，以改善他们的稳定性，即使是以增加变异性为代价。(C)2005爱思唯尔有限公司。保留所有权利。
A ubiquitous characteristic of elderly and patients with gait disabilities is that they walk slower than healthy controls. Many clinicians assume these patients walk slower to improve their stability, just as healthy people slow down when walking across ice. However, walking slower also leads to greater variability, which is often assumed to imply deteriorated stability. If this were true, then slowing down would be completely antithetical to the goal of maintaining stability. This study sought to resolve this paradox by directly quantifying the sensitivity of the locomotor system to local perturbations that are manifested as natural kinematic variability. Eleven young healthy subjects walked on a motorized treadmill at five different speeds. Three-dimensional movements of a single marker placed over the first thoracic vertebra were recorded during continuous walking. Mean stride-to-stride standard deviations and maximum finite-time Lyapunov exponents were computed for each time series to quantify the variability and local dynamic stability, respectively, of these movements. Quadratic regression analyses of the dependent measures vs. walking speed revealed highly significant U shaped trends for all three mean standard deviations, but highly significant linear trends, with significant or nearly significant quadratic terms, for five of the six finite-time Lyapunov exponents. Subjects exhibited consistently better local dynamic stability at slower speeds for these five measures. These results support the clinically based intuition that people who are at increased risk of falling walk slower to improve their stability, even at the cost of increased variability. (c) 2005 Elsevier Ltd. All rights reserved.