Poor dynamic balance, such as poor walking stability, is a hallmark of multiple sclerosis. Instrumental measures of local dynamic stability (LDS, e.g. short-term Lyapunov’s exponents, sLyEs) are genuine measures of walking stability and increasingly used as dynamic balance indicators. The current work aims to investigate if people with multiple sclerosis (PWMS) with no clinical evidence of gait impairment suffer poor LDS of gait. Eighty PWMS with minimal impairment (EDSS ≤2.5) and twenty controls completed the Six-Minute Walk Test (6MWT) at their maximum speed, wearing inertial sensors. sLyEs were calculated from trunk vertical, mediolateral and anteroposterior (sLyE _AP ) acceleration. PWMS also completed a full clinical assessment including gait, balance and fatigue. Gait speed was lower in PWMS than controls (−15%), while sLyEs were larger in PWMS (+12%), even when adjusting for the different gait speed. High sLyE _AP was associated with low gait speed, high impact of disease (including high fatigue) and poor balance, the three variables returned by a principal component analysis of the dataset of clinical measures. PWMS suffer poor LDS of gait, as indicated by large sLyEs. The association between high sLyE _AP and poor balance supports the validity of sLyE _AP as a dynamic balance measure. The inverse relationship between sLyE _AP and gait speed is in line with the view that good balance is decisive for high gait speed. Finally, these findings are in line with the vicious circle linking poor balance and fatigue in PWMS, with fatigue worsening balance and poor balance leading to fatigue.

中文翻译：

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早期多发性硬化症和无轻度神经功能障碍者的步态局部动态稳定性

动平衡差，例如步行稳定性差，是多发性硬化症的标志。局部动态稳定性的度量工具（LDS，例如短期李雅普诺夫指数，sLyEs）是步行稳定性的真实度量，并越来越多地用作动态平衡指标。当前的工作旨在调查没有步态障碍临床证据的多发性硬化症（PWMS）患者是否患有较差的步态LDS。带有惯性传感器的八十个最小损伤（EDSS≤2.5）的PWMS和二十个控件以最大速度完成了六分钟步行测试（6MWT）。sLyEs是通过躯干垂直，中外侧和前后位（sLyE _AP ）加速。PWMS还完成了包括步态，平衡和疲劳在内的全面临床评估。PWMS中的步态速度低于对照组（−15％），而PWM中的sLyEs较大（+ 12％），即使针对不同的步态速度进行了调整。高sLyE _AP与步态速度低，疾病影响大（包括高疲劳）和平衡差有关，这是通过临床测量数据集的主成分分析返回的三个变量。如较大的sLyEs所示，PWMS的步态LDS较差。高sLyE _AP和平衡差之间的关联 支持sLyE _AP作为动态平衡指标的有效性 。sLyE _AP之间的逆关系 步态速度与高步态决定性的平衡是一致的。最后，这些发现与恶性循环相吻合，恶性循环将PWMS的平衡性和疲劳性联系在一起，疲劳使平衡性恶化，平衡性差导致疲劳。