Taylor J L, Gandevia S C
Prince of Wales Medical Research Institute and University of New South Wales, Barker Street, Randwick, Sydney, NSW 2031, Australia.
Muscle Nerve. 2001 Jan;24(1):18-29. doi: 10.1002/1097-4598(200101)24:1<18::aid-mus2>3.0.co;2-d.
During exercise, changes occur at many sites in the motor pathway, including the muscle fiber, motoneuron, motor cortex, and "upstream" of the motor cortex. Some of the changes result in fatigue, which can be defined as a decrease in ability to produce maximal muscle force voluntarily. Transcranial magnetic stimulation (TMS) over the human motor cortex reveals changes in both motor evoked potentials (MEPs) and the silent period during and after fatiguing voluntary contractions in normal subjects. The relationship of these changes to loss of force or fatigue is unclear. However, during a sustained maximal contraction TMS evokes extra force from the muscle and thus demonstrates the development of suboptimal output from the motor cortex, that is, fatigue at a supraspinal level. In some patients with symptoms of fatigue, the response to TMS after exercise is altered, but the changed MEP behavior is not yet linked to particular symptoms or pathology.
在运动过程中，运动通路的许多部位都会发生变化，包括肌纤维、运动神经元、运动皮层以及运动皮层的“上游”。其中一些变化会导致疲劳，疲劳可定义为自愿产生最大肌肉力量的能力下降。对人类运动皮层进行经颅磁刺激（TMS）可揭示正常受试者在疲劳性自愿收缩期间及之后运动诱发电位（MEP）和静息期的变化。这些变化与力量丧失或疲劳之间的关系尚不清楚。然而，在持续的最大收缩过程中，TMS会从肌肉中诱发额外的力量，从而证明运动皮层出现了次优输出，即脊髓以上水平的疲劳。在一些有疲劳症状的患者中，运动后对TMS的反应会发生改变，但MEP行为的改变尚未与特定症状或病理状况相关联。
