Background

Motor fatigability (i.e. contraction-induced reduction in muscle strength) from a concentric task associate stronger to walking and perception of fatigue in persons with multiple sclerosis (pwMS), compared with an isometric task. However, the central and peripheral contributions of motor fatigability between these tasks have not been investigated.

Objective

Compare the central and peripheral contributions of motor fatigability in the knee extensors in a sustained isometric fatigability protocol versus a concentric fatigability protocol and in pwMS versus healthy controls (HCs).

Methods

Participants (n=31 pwMS; n=15 HCs) underwent neuromuscular testing before and immediately after two knee extensor fatigability tasks (sustained isometric and concentric) in an isokinetic dynamometer. Neuromuscular testing of fatigability consisted of maximal voluntary contraction, voluntary activation (central/neural contributor), and resting twitch (peripheral/muscular contributor) determined by the interpolated twitch technique.

Results

Sustained isometric and concentric fatigability protocols resulted in motor fatigability for both pwMS and HCs, with no between-protocols differences for either group. Regression analysis showed that motor fatigability variance in pwMS was mainly attributed to central fatigability in the sustained isometric protocol and to both central and peripheral fatigability in the concentric protocol. In HCs, the variance in sustained isometric and concentric fatigability were attributed to both peripheral and central fatigability.

Conclusion

Central and peripheral contributions of motor fatigability differed between sustained isometric and concentric protocols as well as between pwMS and HCs. These between-protocol differences in pwMS provide a neuromuscular dimension to the reported difference in the strength of associations of concentric and isometric tasks to walking and perception of fatigue in pwMS.

中文翻译：

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多发性硬化症患者和健康对照者等距和同心运动疲劳的比较——探索运动疲劳的中枢和外周贡献

背景

与等长任务相比，来自同心圆任务的运动疲劳（即收缩引起的肌肉力量降低）与多发性硬化症 (pwMS) 患者的行走和疲劳感知相关性更强。然而，尚未研究这些任务之间运动疲劳的中心和外围贡献。

客观的

比较持续等长疲劳性协议与同心疲劳性协议以及 pwMS 与健康对照 (HCs) 中膝关节伸肌运动疲劳性的中心和外周贡献。

方法

参与者（n = 31 pwMS；n = 15 HC）在等速测力计中进行两次膝关节伸肌疲劳任务（持续等长和同心）之前和之后立即进行神经肌肉测试。疲劳性的神经肌肉测试包括由插值抽搐技术确定的最大自主收缩、自主激活（中枢/神经贡献者）和静息抽搐（外周/肌肉贡献者）。

结果

持续的等距和同心疲劳协议导致 pwMS 和 HC 的运动疲劳，两组的协议之间没有差异。回归分析表明，pwMS 中的运动易疲劳性差异主要归因于持续等长方案中的中枢易疲劳性以及同心方案中的中枢和外周易疲劳性。在 HCs 中，持续等长和同心易疲劳性的差异归因于外周和中枢易疲劳性。

结论

运动疲劳的中枢和外周贡献在持续等长和同心协议之间以及 pwMS 和 HC 之间有所不同。pwMS 中的这些协议间差异为所报告的同心和等距任务与行走和 pwMS 疲劳感知的关联强度差异提供了神经肌肉维度。