Background

Automatic postural responses are critical to prevent falls after a loss of balance. Although responses have been shown to be delayed in people with multiple sclerosis (PwMS), the degree to which other aspects of these movements are impacted by MS remains unknown.

Research Question

Do responses to in-place support-surface perturbations differ in PwMS compared to neurotypical adults? Are these responses related to a functional measure of postural response performance- center of mass (COM) displacement?.

Method

52 PwMS and 20 neurotypical, age-matched adults (NA) experienced backward support surface perturbations resulting in forward loss of balance and requiring an in-place response. Center of pressure (COP) and torque were calculated from force plates while center of mass (COM) approximations were collected via motion capture. Primary outcomes were maximal torque production at the foot and its timing, rate, and onset.

Results

PwMS and NA demonstrated no differences in maximal torque production (p = 0.79), timing of maximal torque (p = 0.29), rate of torque development (p = 0.76), or the onset of AP COP movement (p = 0.44). There was a significant negative association between the rate of torque development and forward COM displacement in both groups (Control: r=-0.64, p = 0.002; MS: r=-0.35, p = 0.01). Larger maximal torque production was also associated with smaller COM displacement in PwMS (r=-0.33, p = 0.02).

Conclusion

Torque profiles in response to backward support surface translations resulting in feet in-place responses were similar in people with mild MS and neurotypical adults. The rate of development and maximal torque were however correlated to functional postural response outcomes. These findings suggest that while not worse in PwMS during in-place perturbations, force-responses seem to be important predictors of the effectiveness of reactive postural control responses.

中文翻译：

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多发性硬化症患者对原位摄动的扭矩反应

背景

自动姿势响应对于防止失去平衡后的跌倒至关重要。尽管已显示多发性硬化症（PwMS）患者的反应延迟，但MS对这些运动的其他方面的影响程度仍然未知。

研究问题

与典型的成年人相比，PwMS对原位支持表面微扰的反应是否有所不同？这些反应与姿势反应性能-质心（COM）位移的功能测量有关吗？

方法

52个PwMS和20个典型的年龄匹配的神经型成年人（NA）经历了向后的支撑表面扰动，导致向前失去平衡并需要就地响应。从测力板计算压力中心（COP）和扭矩，同时通过运动捕获收集质量中心（COM）近似值。主要结果是足部产生最大扭矩，以及其时机，速度和发作。

结果

PwMS和NA在最大扭矩产生（p = 0.79），最大扭矩计时（p = 0.29），扭矩产生速率（p = 0.76）或AP COP运动开始（p = 0.44）方面无差异。两组的转矩发展速度和前向COM位移之间存在显着的负相关性（对照：r = -0.64，p = 0.002； MS：r = -0.35，p = 0.01）。最大的扭矩产生也与PwMS中的COM位移较小有关（r = -0.33，p = 0.02）。

结论

在轻度MS和神经型成年人中，响应向后支撑表面平移而导致脚就位响应的扭矩曲线相似。然而，发育速度和最大扭矩与功能性姿势反应结果相关。这些发现表明，尽管在原位摄动过程中PwMS并不较差，但力反应似乎是反应性姿势控制反应有效性的重要预测指标。