Background. Fatigue is one of the most frequent symptoms in persons with multiple sclerosis (MS). Distinction is made between subjective perceptions of fatigue and objective measures of fatigability. Fatigability can be measured by different protocols. Yet no studies have compared isometric and concentric contraction protocols of the lower extremities head-to-head. Therefore, the purpose of the present study was to (1) compare 2 such protocols head-to-head and (2) to investigate the association between fatigability evoked by the 2 protocols and measures of fatigue and walking. Methods. A total of 45 patients with MS had their walking capacity measured objectively by the 6-minute walk test (6MWT) and subjectively by the 12-item Multiple Sclerosis Walking Scale (MSWS-12). Fatigue was measured by the Modified Fatigue Impact Scale (MFIS) and fatigability by 2 knee extension protocols: sustained isometric and concentric. Results. The sustained isometric protocol induced a higher degree of fatigability than the concentric protocol (P < .01). Regression analyses revealed that sustained isometric fatigability was not associated with either measures of fatigue or walking (all r2 = 0.00; P = .85-.99), whereas the concentric protocol was significantly associated with fatigue (r2 = 0.20; P < .01), 6MWT (r2 = 0.09; P < .05), and MSWS-12 (r2 = 0.16; P < .01). Furthermore, after adjusting for maximal strength and sex, concentric fatigability remained a strong and significant predictor of fatigue (β = 0.49) and walking (6MWT: β = −0.26; MSWS: β = 0.37). Conclusion. This study provides the first evidence that a lower-extremity concentric fatigability protocol provides superior reflection of both fatigue and walking when compared with a sustained isometric protocol. We suggest that concentric protocols should be the focus of future studies investigating fatigability.

中文翻译：

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等距和同心疲劳协议的头对头比较以及与多发性硬化症患者的疲劳和步行的关联

背景。疲劳是多发性硬化症 (MS) 患者最常见的症状之一。对疲劳的主观感知和对疲劳的客观测量有所区别。疲劳度可以通过不同的协议来测量。然而，没有研究比较过头对头下肢的等长收缩和向心收缩方案。因此，本研究的目的是 (1) 头对头比较 2 个这样的协议，(2) 调查由 2 个协议引起的易疲劳性与疲劳和步行的测量之间的关联。方法。共有 45 名 MS 患者的步行能力通过 6 分钟步行测试 (6MWT) 进行客观测量，并通过 12 项多发性硬化症步行量表 (MSWS-12) 进行主观测量。疲劳通过修正疲劳影响量表 (MFIS) 测量，疲劳通过 2 种膝关节伸展方案测量：持续等长和同心。结果。持续等长方案比同心方案引起更高程度的疲劳（P < .01）。回归分析显示，持续等长疲劳与疲劳或步行测量无关（所有 r2 = 0.00；P = .85-.99），而同心方案与疲劳显着相关（r2 = 0.20；P < .01 )、6MWT (r2 = 0.09; P < .05) 和 MSWS-12 (r2 = 0.16; P < .01)。此外，在调整最大力量和性别后，向心疲劳仍然是疲劳（β = 0.49）和步行（6MWT：β = -0.26；MSWS：β = 0.37）的一个强大而重要的预测因子。结论。这项研究提供了第一个证据，证明与持续等长方案相比，下肢向心疲劳方案可以更好地反映疲劳和步行。我们建议同心协议应该是未来研究易疲劳性的重点。