Kazanski Meghan E, Cusumano Joseph P, Dingwell Jonathan B
Department of Kinesiology & Health Education, University of Texas, Austin, TX 78712, USA; Department of Kinesiology, Pennsylvania State University, University Park, PA 16802, USA.
Department of Engineering Science & Mechanics, Pennsylvania State University, University Park, PA 16802, USA.
J Biomech. 2020 May 7;104:109714. doi: 10.1016/j.jbiomech.2020.109714. Epub 2020 Feb 25.
Gait variability is generally associated with falls, but specific connections remain disputed. To reduce falls, we must first understand how older adults maintain lateral balance while walking, particularly when their stability is challenged. We recently developed computational models of lateral stepping, based on Goal Equivalent Manifolds, that separate effects of step-to-step regulation from variability. These show walking humans seek to strongly maintain step width, but also lateral position on their path. Here, 17 healthy older (ages 60+) and 17 healthy young (ages 18-31) adults walked in a virtual environment with no perturbations and with laterally destabilizing perturbations of either the visual field or treadmill platform. For step-to-step time series of step widths and lateral positions, we computed variability, statistical persistence and how much participants directly corrected deviations at each step. All participants exhibited significantly increased variability, decreased persistence and tighter direct control when perturbed. Simulations from our stepping regulation models indicate people responded to the increased variability imposed by these perturbations by either maintaining or tightening control of both step width and lateral position. Thus, while people strive to maintain lateral balance, they also actively strive to stay on their path. Healthy older participants exhibited slightly increased variability, but no differences from young in stepping regulation and no evidence of greater reliance on visual feedback, even when subjected to substantially destabilizing perturbations. Thus, age alone need not degrade lateral stepping control. This may help explain why directly connecting gait variability to fall risk has proven difficult.
步态变异性通常与跌倒相关，但具体联系仍存在争议。为了减少跌倒，我们必须首先了解老年人在行走时如何保持侧向平衡，尤其是在其稳定性受到挑战时。我们最近基于目标等效流形开发了侧向跨步的计算模型，该模型将逐步调节的影响与变异性分开。这些模型表明，行走的人试图强烈保持步幅宽度，同时也保持其路径上的侧向位置。在这里，17名健康的老年人（60岁以上）和17名健康的年轻人（18 - 31岁）在虚拟环境中行走，该环境无干扰以及存在视野或跑步机平台的侧向不稳定干扰。对于步幅宽度和侧向位置的逐步时间序列，我们计算了变异性、统计持续性以及参与者在每一步直接纠正偏差的程度。所有参与者在受到干扰时均表现出变异性显著增加、持续性降低以及直接控制更紧密。我们的跨步调节模型模拟表明，人们通过保持或加强对步幅宽度和侧向位置的控制来应对这些干扰所带来的增加的变异性。因此，虽然人们努力保持侧向平衡，但他们也积极努力保持在自己的路径上。健康的老年参与者表现出变异性略有增加，但在跨步调节方面与年轻人没有差异，并且即使受到严重的不稳定干扰，也没有证据表明他们更依赖视觉反馈。因此，仅年龄本身不一定会降低侧向跨步控制能力。这可能有助于解释为什么将步态变异性与跌倒风险直接联系起来一直很困难。
