Kent-Braun J A, Sharma K R, Weiner M W, Miller R G
Department of Radiology, University of California, San Francisco.
Muscle Nerve. 1994 Oct;17(10):1162-9. doi: 10.1002/mus.880171006.
We investigated the role of metabolism in muscle fatigue during voluntary exercise in persons with mild multiple sclerosis (MS). Six MS and 8 healthy control subjects performed intermittent, progressive, isometric contractions of the ankle dorsiflexors, during which we measured maximum voluntary force (MVC), inorganic phosphate (Pi), phosphocreatine (PCr), and pH. During exercise, MVC fell sooner in MS, but by the end of exercise the relative decrease in MVC was similar in both groups. In contrast, at the end of exercise Pi/PCr increased to 1.86 +/- 0.22 in controls but to only 0.66 +/- 0.04 in MS (P < 0.01); likewise, pH was 6.75 +/- 0.04 in controls and unchanged (7.06 +/- 0.04) in MS (P < 0.01). The smaller metabolic change at the same relative exercise intensity suggests a failure of muscle activation that is present even in mild MS. Neurophysiologic measures of activation indicated some central activation failure and no neuromuscular junction impairment in MS, and suggested that activation failure beyond the muscle membrane (excitation-contraction coupling) may be important in MS. We conclude that metabolic factors do not play a significant role in the development of muscle fatigue during voluntary exercise in mild MS.
我们研究了新陈代谢在轻度多发性硬化症（MS）患者自主运动期间肌肉疲劳中的作用。6名MS患者和8名健康对照者进行了踝关节背屈肌的间歇性、渐进性等长收缩，在此期间我们测量了最大自主收缩力（MVC）、无机磷酸盐（Pi）、磷酸肌酸（PCr）和pH值。运动过程中，MS患者的MVC下降得更快，但在运动结束时，两组MVC的相对下降幅度相似。相比之下，运动结束时，对照组的Pi/PCr升高至1.86±0.22，而MS患者仅为0.66±0.04（P<0.01）；同样，对照组的pH值为6.75±0.04，而MS患者无变化（7.06±0.04）（P<0.01）。在相同相对运动强度下较小的代谢变化表明，即使在轻度MS患者中也存在肌肉激活障碍。激活的神经生理学测量表明，MS患者存在一些中枢激活障碍，且无神经肌肉接头损伤，并提示肌肉膜外的激活障碍（兴奋-收缩偶联）在MS中可能很重要。我们得出结论，在轻度MS患者的自主运动期间，代谢因素在肌肉疲劳的发展中不发挥重要作用。
