Background

Challenging children with Down syndrome to walk fast and with external ankle load has demonstrated acute adjustments, such as increased step length and decreased step width, and improved joint stability. However, it is unknown to what extent these task constraints affect gait stability. Assessing dynamic gait stability through margin-of-stability not only quantifies adjustments related to balance control, but also informs safety considerations.

Methods

Twenty-four children with and without Down syndrome participated in this study. Subjects walked overground at two speed conditions: self-selected (normal) and as fast as possible (fast); and two ankle load conditions: no load and ankle load of 2% body mass. We assessed margin-of-stability in the anteroposterior and mediolateral directions, separately, at three gait events of toe-off, mid-swing, and heel strike.

Findings

Children with Down syndrome walked with greater mediolateral margin-of-stability than typically developing children. Children with Down syndrome demonstrated less anteroposterior margin-of-stability than typically developing children only before heel-strike at normal speed but increased anteroposterior margin-of-stability at fast speed. The ankle load increased the mediolateral margin-of-stability in both groups but did not impact the anteroposterior margin-of-stability. In addition, children with Down syndrome took shorter and wider steps for more lateral placement of mediolateral margin-of-stability.

Interpretation

Children with Down syndrome were capable of adjusting their margin-of-stability for fast walking and ankle-load conditions. However, children with Down syndrome walked with less mediolateral stability and anteroposterior mobility than typically developing children. Children with Down syndrome overcompensate the mediolateral foot placement to recapture their margin-of-stability and maintain gait stability.

中文翻译：

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患有和不患有唐氏综合症的儿童在地上行走时的动态步态稳定性

背景

挑战患有唐氏综合症的儿童在踝关节外部负重的情况下快速行走已表现出急性调整，例如增加步长和减少步宽，并改善关节稳定性。然而，尚不清楚这些任务限制在多大程度上影响步态稳定性。通过稳定裕度评估动态步态稳定性不仅可以量化与平衡控制相关的调整，还可以提供安全考虑。

方法

二十四名患有和不患有唐氏综合症的儿童参加了这项研究。受试者以两种速度条件在地面上行走：自主选择（正常）和尽可能快（快速）；以及两种踝关节负载条件：无负载和2%体重的踝关节负载。我们分别评估了脚趾离地、摆动中期和脚跟着地这三个步态事件的前后方向和内侧方向的稳定性裕度。

发现

患有唐氏综合症的儿童行走时比正常发育的儿童具有更大的内侧稳定裕度。患有唐氏综合症的儿童仅在以正常速度足跟着地之前表现出比正常发育儿童更少的前后稳定裕度，但在快速速度下前后稳定裕度增加。踝关节负荷增加了两组的内侧稳定边际，但不影响前后稳定边际。此外，患有唐氏综合症的儿童会采取更短、更宽的步子，以获得更多的侧向稳定边际。

解释

患有唐氏综合症的儿童能够根据快速行走和脚踝负荷情况调整稳定裕度。然而，与正常发育的儿童相比，患有唐氏综合症的儿童行走时的中外侧稳定性和前后活动能力较差。患有唐氏综合症的儿童过度补偿脚的内侧放置位置，以重新获得稳定裕度并保持步态稳定性。