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

运动疲劳在健康人中是一种常见的经历，在许多疾病中可能是一个问题。由于疲劳，人们用肌肉产生力量的能力较差。这种虚弱在很大程度上是由于肌肉发生的事件，但也有一些是神经系统变化的结果。神经系统对疲劳的贡献大小，目前尚不清楚在日常生活中会导致疲劳的运动类型，例如，手持购物或一盘食物等持续的微弱收缩，步行或粉刷墙壁等有节奏的收缩，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在疲劳时的行为会发生变化，但其中许多变化是如何发生的，为什么会发生，以及它们是如何影响运动控制的，人们对此知之甚少。计划采取三种方法。在第一组研究中，我们将使用大脑和神经刺激来衡量持续的低水平活动对人们充分驱动肌肉的能力的影响。我们将确定这种活动以及对身体其他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的变化是否会改变人们在疲惫的运动任务中的表现，或者他们对这些任务需要付出多大努力的看法。最后，我们将使用脊髓刺激来找出为什么脊髓中的运动神经细胞因疲劳而燃烧得更慢。疲劳是一种重要的症状，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、慢性阻塞性呼吸道疾病、抑郁症和癌症以及化疗、手术和病毒性疾病后的主要主诉。更好地了解神经系统对疲劳的贡献的意义从患者的靶向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.