How Changes in the Motor Cortex and Spinal Cord with Exercise Contribute to Fatigue in Humans

运动疲劳是健康人的常见经历，也可能是许多疾病的问题。随着疲劳的人是不太能够产生的力量与他们的肌肉。这种虚弱的发生大部分是因为肌肉中的事件，但也有一些是由于神经系统的变化。神经系统对疲劳的贡献的大小并不知道日常生活中导致疲劳的运动种类，例如长时间的弱收缩，如拿着购物或一盘食物，有节奏的收缩，如走路或粉刷墙壁，以及导致呼吸和体温变化的更剧烈的运动。大脑和脊髓中的神经细胞的行为在疲劳时会发生改变，但这些变化是如何以及为什么发生的，以及它们如何影响运动的控制，目前还知之甚少。计划采取三种办法。在第一组研究中，我们将使用大脑和神经刺激来测量持续低水平活动对人们充分驱动肌肉能力的影响。我们将确定这些活动以及对其他身体系统的需求增加是否会导致神经系统疲劳。在第二组研究中，我们将调查大脑运动区域的变化是否会改变人们对疲劳运动任务的表现，或者他们对任务需要付出多少努力的感知。最后，我们将使用脊髓刺激来研究为什么脊髓中的运动神经细胞在疲劳时发射得更慢。疲劳是一种重要的症状，它并不局限于身体任何一个系统的疾病。例如，它是多发性硬化症、心力衰竭、慢性阻塞性气道疾病、抑郁症和癌症以及化疗、手术和病毒性疾病后的主要主诉。更好地理解神经系统对疲劳的贡献的意义范围从针对患者的治疗到提高运动员的表现。

Fatigue with exercise is a common experience in healthy people and can be a problem in many illnesses. With fatigue people are less able to produce force with their muscles. Much of this weakness occurs because of events in the muscles but some results from changes in the nervous system. The size of the contribution of the nervous system to fatigue is not known for the kinds of exercise that cause fatigue in everyday life e.g. prolonged weak contractions like holding the shopping or a plate of food, rhythmic contractions like walking or painting a wall, and more vigorous exercise that causes changes in breathing and body temperature. The behaviour of nerve cells in the brain and spinal cord is altered in fatigue but how and why many of these changes occur, and how they affect the control of movements, is poorly understood. Three approaches are planned. In the first set of studies, we will use brain and nerve stimulation to measure the impact of sustained low-level activities on people's ability to drive their muscles fully. We will identify whether such activities, as well as increased demands on other body systems, can cause fatigue in the nervous system. In the second set of studies, we will investigate whether changes in the motor areas of the brain can alter peoples' performance of fatiguing motor tasks or their perception of how much effort the tasks take. Finally, we will use stimulation of the spinal cord to work out why motor nerve cells in the spinal cord fire more slowly with fatigue. Fatigue is an important symptom which is not confined to diseases of any one system in the body. For example, it is a major complaint in multiple sclerosis, cardiac failure, chronic obstructive airway disease, depression and cancer, as well as after chemotherapy, surgery, and viral illness. The implications of better understanding of the contribution of the nervous system to fatigue range from targeting treatments in patients to improving the performance of athletes.