Abstract：
BACKGROUND: Older adults have difficulty maintaining side-to-side balance while navigating daily environments. Losing balance in such circumstances can lead to falls. We need to better understand how older adults adapt lateral balance to navigate environment-imposed task constraints.
OBJECTIVE: How do older adults adjust mediolateral balance while walking along continually-narrowing paths, and what are the stability implications of these adjustments?
METHODS: Eighteen older (71.6±6.0 years) and twenty younger (21.7±2.6 years) healthy adults traversed 25 m-long paths that gradually narrowed from 45 cm to 5 cm. Participants switched onto an adjacent path when they chose. We quantified participants\' lateral center-of-mass dynamics and lateral Margins of Stability (MoSL) as paths narrowed. We quantified lateral Probability of Instability (PoIL) as the probability that participants would take a laterally unstable (MoSL<0) step as they walked. We also extracted these outcomes where participants switched paths.
RESULTS: As paths narrowed, all participants exhibited progressively smaller average MoSL and increasingly larger PoIL. However, their MoSL variability was largest at both the narrowest and widest path sections. Older adults exhibited consistently both larger average and more variable MoSL across path widths. Taken into account together, these resulted in either comparable or somewhat larger PoIL as paths narrowed. Older adults left the narrowing paths sooner, on average, than younger. As they did so, older adults exhibited significantly larger average and more variable MoSL, but somewhat smaller PoIL than younger.
CONCLUSIONS: Our results directly challenge the predominant interpretation that larger average MoSL indicate \"greater stability\", which we argue is inconsistent with the principles underlying its derivation. In contrast, analyzing step-to-step gait dynamics, together with estimating PoIL allows one to properly quantify instability risk. Furthermore, the adaptive strategies uncovered using these methods suggest potential targets for future interventions to reduce falls in older adults.
OBJECTIVE: How do older adults adjust mediolateral balance while walking along continually-narrowing paths, and what are the stability implications of these adjustments?
METHODS: Eighteen older (71.6±6.0 years) and twenty younger (21.7±2.6 years) healthy adults traversed 25 m-long paths that gradually narrowed from 45 cm to 5 cm. Participants switched onto an adjacent path when they chose. We quantified participants\' lateral center-of-mass dynamics and lateral Margins of Stability (MoSL) as paths narrowed. We quantified lateral Probability of Instability (PoIL) as the probability that participants would take a laterally unstable (MoSL<0) step as they walked. We also extracted these outcomes where participants switched paths.
RESULTS: As paths narrowed, all participants exhibited progressively smaller average MoSL and increasingly larger PoIL. However, their MoSL variability was largest at both the narrowest and widest path sections. Older adults exhibited consistently both larger average and more variable MoSL across path widths. Taken into account together, these resulted in either comparable or somewhat larger PoIL as paths narrowed. Older adults left the narrowing paths sooner, on average, than younger. As they did so, older adults exhibited significantly larger average and more variable MoSL, but somewhat smaller PoIL than younger.
CONCLUSIONS: Our results directly challenge the predominant interpretation that larger average MoSL indicate \"greater stability\", which we argue is inconsistent with the principles underlying its derivation. In contrast, analyzing step-to-step gait dynamics, together with estimating PoIL allows one to properly quantify instability risk. Furthermore, the adaptive strategies uncovered using these methods suggest potential targets for future interventions to reduce falls in older adults.
摘要：
背景：老年人在日常环境中导航时难以保持左右平衡。在这种情况下失去平衡会导致跌倒。我们需要更好地了解老年人如何适应横向平衡以适应环境施加的任务限制。
目的：老年人在不断变窄的小路中行走时如何调整中外侧平衡，这些调整的稳定性含义是什么？
方法：18位年龄较大（71.6±6.0岁）的健康成年人和20位年龄较小（21.7±2.6岁）的健康成年人穿越了25m长的路径，逐渐从45cm缩小到5cm。参与者在选择时切换到相邻的路径。我们将参与者的横向质心动态和横向稳定边际(MoSL)量化为路径变窄。我们将横向不稳定概率（PoIL）量化为参与者在行走时采取横向不稳定（MoSL<0）步骤的概率。我们还提取了参与者切换路径的这些结果。
结果：随着路径变窄，所有参与者表现出逐渐变小的平均MoSL和越来越大的PoIL.然而,它们的MoSL变异性在最窄和最宽的路段都最大。老年人在路径宽度上始终表现出更大的平均值和更多的可变MoSL。一起考虑，随着路径变窄，这些导致了可比的或稍大的PoIL。老年人更快离开狭窄的道路，平均而言,比年轻。当他们这样做的时候，老年人表现出显著更大的平均水平和更多的变化MoSL，但有点小PoIL比年轻。
结论：我们的结果直接挑战了主要的解释，即平均MoSL越大表明“稳定性越大”，我们认为这与它的推导背后的原则不一致。相比之下,分析一步一步的步态动力学，与估计PoIL一起，可以正确量化不稳定风险。此外，使用这些方法发现的适应性策略为减少老年人跌倒的未来干预措施提供了潜在目标.
目的：老年人在不断变窄的小路中行走时如何调整中外侧平衡，这些调整的稳定性含义是什么？
方法：18位年龄较大（71.6±6.0岁）的健康成年人和20位年龄较小（21.7±2.6岁）的健康成年人穿越了25m长的路径，逐渐从45cm缩小到5cm。参与者在选择时切换到相邻的路径。我们将参与者的横向质心动态和横向稳定边际(MoSL)量化为路径变窄。我们将横向不稳定概率（PoIL）量化为参与者在行走时采取横向不稳定（MoSL<0）步骤的概率。我们还提取了参与者切换路径的这些结果。
结果：随着路径变窄，所有参与者表现出逐渐变小的平均MoSL和越来越大的PoIL.然而,它们的MoSL变异性在最窄和最宽的路段都最大。老年人在路径宽度上始终表现出更大的平均值和更多的可变MoSL。一起考虑，随着路径变窄，这些导致了可比的或稍大的PoIL。老年人更快离开狭窄的道路，平均而言,比年轻。当他们这样做的时候，老年人表现出显著更大的平均水平和更多的变化MoSL，但有点小PoIL比年轻。
结论：我们的结果直接挑战了主要的解释，即平均MoSL越大表明“稳定性越大”，我们认为这与它的推导背后的原则不一致。相比之下,分析一步一步的步态动力学，与估计PoIL一起，可以正确量化不稳定风险。此外，使用这些方法发现的适应性策略为减少老年人跌倒的未来干预措施提供了潜在目标.
