Department of Anaesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, AN2041, Blegdamsvej 9, DK2100 Copenhagen, Denmark.
J Physiol. 2010 Jun 1;588(Pt 11):1985-95. doi: 10.1113/jphysiol.2009.186767. Epub 2010 Apr 19.
Maximal exercise may be limited by central fatigue defined as an inability of the central nervous system to fully recruit the involved muscles. This study evaluated whether a reduction in the cerebral oxygen-to-carbohydrate index (OCI) and in the cerebral mitochondrial oxygen tension relate to the ability to generate a maximal voluntary contraction and to the transcranial magnetic stimulated force generation. To determine the role of a reduced OCI and in central fatigue, 16 males performed low intensity, maximal intensity and hypoxic cycling exercise. Exercise fatigue was evaluated by ratings of perceived exertion (RPE), arm maximal voluntary force (MVC), and voluntary activation of elbow flexor muscles assessed with transcranial magnetic stimulation. Low intensity exercise did not produce any indication of central fatigue or marked cerebral metabolic deviations. Exercise in hypoxia (0.10) reduced cerebral oxygen delivery 25% and decreased 11+/-4 mmHg (P<0.001) together with OCI (6.2+/-0.7 to 4.8+/-0.5, P<0.001). RPE increased while MVC and voluntary activation were reduced (P<0.05). During maximal exercise declined 8+/-4 mmHg (P<0.05) and OCI to 3.8+/-0.5 (P<0.001). RPE was 18.5, and MVC and voluntary activation were reduced (P<0.05). We observed no signs of muscular fatigue in the elbow flexors and all control MVCs were similar to resting values. Exhaustive exercise provoked cerebral deoxygenation, metabolic changes and indices of fatigue similar to those observed during exercise in hypoxia indicating that reduced cerebral oxygenation may play a role in the development of central fatigue and may be an exercise capacity limiting factor.
最大运动可能受到中枢疲劳的限制，定义为中枢神经系统无法充分募集参与的肌肉。本研究评估了脑氧-碳水化合物指数（OCI）和脑线粒体氧张力的降低是否与产生最大随意收缩和经颅磁刺激力产生的能力相关。为了确定 OCI 和中枢疲劳降低的作用，16 名男性进行了低强度、最大强度和低氧自行车运动。通过感觉用力评分（RPE）、手臂最大随意力（MVC）和经颅磁刺激评估的肘屈肌自愿激活来评估运动疲劳。低强度运动没有产生任何中枢疲劳或明显的脑代谢偏差的迹象。在低氧（0.10）下运动降低了脑氧输送 25%，并降低了 11+/-4mmHg（P<0.001），同时 OCI 降低（6.2+/-0.7 至 4.8+/-0.5，P<0.001）。RPE 增加，而 MVC 和自愿激活降低（P<0.05）。在最大运动中下降了 8+/-4mmHg（P<0.05），OCI 降低至 3.8+/-0.5（P<0.001）。RPE 为 18.5，MVC 和自愿激活降低（P<0.05）。我们在肘屈肌中没有观察到肌肉疲劳的迹象，并且所有的对照 MVC 与静息值相似。竭尽性运动引起脑缺氧、代谢变化和疲劳指标与低氧运动中观察到的相似，表明脑氧合降低可能在中枢疲劳的发展中起作用，并且可能是运动能力的限制因素。
