How Changes In The Motor Cortex And Spinal Cord With Exercise Contribute To Fatigue In Humans
Funder
National Health and Medical Research Council
Funding Amount
$311,250.00
Summary
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 f ....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.Read moreRead less
I am a neurophysiologist who examines the neural control of movement and the interaction of sensation and movement in human subjects. I study cortical and motoneuronal events during exercise and muscle fatigue. I also study proprioception i.e. the sensati
Cortical, Descending And Reflex Control Of Human Inspiratory Muscles
Funder
National Health and Medical Research Council
Funding Amount
$324,500.00
Summary
Of all the skeletal muscles, the breathing muscles perform the most crucial action, that is, they maintain ventilation. The neural control of respiratory muscles must be finely integrated to maintain ventilation while we are awake, asleep, exercising, eating and talking. The neural circuitry for the respiratory muscles is unique. Control of respiratory muscles differs from that of limb muscles because the respiratory motoneurones are activated rhythmically but are controlled via two descending p ....Of all the skeletal muscles, the breathing muscles perform the most crucial action, that is, they maintain ventilation. The neural control of respiratory muscles must be finely integrated to maintain ventilation while we are awake, asleep, exercising, eating and talking. The neural circuitry for the respiratory muscles is unique. Control of respiratory muscles differs from that of limb muscles because the respiratory motoneurones are activated rhythmically but are controlled via two descending pathways. During automatic breathing, descending neural drive arises from the central respiratory pattern generator in the brainstem. Through this system, disturbances are reflexly compensated for without conscious effort. However, in addition, to automatic control, respiration can also be controlled voluntarily from the motor cortex, for example during speech or a breath hold. However, in humans the neural connections and interactions between these two centres are poorly understood. In addition to descending signals, the activity of inspiratory muscles is affected by sensory reflex inputs. The proposed studies will investigate three aspects of the control of human inspiratory muscles that act to 'pump' air into the lungs and upper airway 'dilator' muscles that act to keep the airway open. Because expiration is usually passive during quiet breathing we will focus on the neural control of inspiration. First, we will investigate some of the reflex connections of human 'pump' and 'dilator' muscles in people with and without obstructive sleep apnoea. Second, we will study the descending control of inspiratory muscles using single motor unit recordings. In addition, we will make the first detailed analysis of single motor unit activity from the tongue. This muscle critically helps preserve breathing when we sleep. Finally, we will examine the interactions between the motor cortex and medulla in the control of breathing about which relatively little is known in awake humans.Read moreRead less