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
Muscle fatigue is common after exercise in healthy people. In many tasks, some muscles become more fatigued than others. Thus, the nervous system must often coordinate fatigued muscles (which produce less force) with unfatigued muscles. We will investigate how fatigue of one muscle alters the way the brain controls other muscles that are engaged in the same task or in unrelated tasks. This will aid understanding of the failures of coordination that lead to poor performance and injury.
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
Changes In Motor Control And Kinaesthetic Sensations After Eccentric Exercise.
Funder
National Health and Medical Research Council
Funding Amount
$287,250.00
Summary
It is a well-known observation that after a period of intense exercise we are unsteady on our feet and are clumsy when attempting to make precision movements. Such impressions are particularly marked after eccentric exercise, during which the contracting muscles are forcibly lengthened. Activities such as walking downhill, skiing and horse riding involve eccentric exercise. The debilitating consequences of this kind of exercise are attributed, not just to the post-exercise effects of fatigue, bu ....It is a well-known observation that after a period of intense exercise we are unsteady on our feet and are clumsy when attempting to make precision movements. Such impressions are particularly marked after eccentric exercise, during which the contracting muscles are forcibly lengthened. Activities such as walking downhill, skiing and horse riding involve eccentric exercise. The debilitating consequences of this kind of exercise are attributed, not just to the post-exercise effects of fatigue, but to loss of muscle force from damage to fibres. Eccentric exercise also leads to longer term effects. The breakdown of the damaged tissue leads to sensations of stiffness and soreness the next day. This application proposes experiments aimed at studying a number of effects of eccentric exercise on motor control, and establishing the muscle, spinal and brain levels at which they occur. Three studies are planned. In the first, the question will be explored whether we are less able to use the motor areas of our brains to execute voluntary contractions after exercise. So fatigue is not just a matter of exhausted muscles but perhaps also exhausted brains. We will use brain and spinal cord stimulation to explore this point. Then we plan to listen to single motor units, the basic elements of muscle control, to try to understand the mechanism by which the brain minimises the debilitating effects of fatigue. Finally we want to examine subjects' ability to locate their limbs in space as a means of providing a basis for the clumsiness we experience after intense exercise. These are all important issues relevant to clinical medicine and rehabilitation as well as sports science and exercise.Read moreRead less
I am a physiologist investigating the molecular basis of normal function in skeletal muscle and the dysfunctions occurring in various muscle diseases and in fatigue. In addition, I investigate analogous dysfunction of calcium release and excitability occu
Energy Use And Work Output By Cross-bridges In Fast- And Slow-twitch Muscles
Funder
National Health and Medical Research Council
Funding Amount
$191,177.00
Summary
All voluntary movement is produced by the action of skeletal muscles. The muscles provide the mechanical power required to move the limbs and the body. To do so, they require energy which is ultimately derived from the breakdown of food. Therefore, we can describe the fundamental process underlying muscular contraction as the conversion of energy from a chemical form into a mechanical form. This project investigates the relationship between the breakdown of molecules that provide energy and the ....All voluntary movement is produced by the action of skeletal muscles. The muscles provide the mechanical power required to move the limbs and the body. To do so, they require energy which is ultimately derived from the breakdown of food. Therefore, we can describe the fundamental process underlying muscular contraction as the conversion of energy from a chemical form into a mechanical form. This project investigates the relationship between the breakdown of molecules that provide energy and the production of mechanical energy or work. Normal contraction involves many cyclic interactions between two proteins, actin and myosin. Each cycle produces a tiny force that contributes to the shortening of the muscle. For over 30 years, it has been thought that energy required for each force producing cycle was provided by the breakdown of one energy-providing molecule, called ATP. Almost all current models of muscle contraction are based on this idea. Recently, data from studies using isolated actin and myosin and observing their interaction in vitro have indicated that many force-producing cycles may be performed with the energy from just one ATP. If this is correct, it will revolutionise our ideas about the way muscles convert chemical energy into mechanical energy. However, the interaction of proteins in a dish is far removed from a normal muscle and the aim of this project is to determine the relationship between force producing cycles and energy use in intact muscles. If multiple force-producing cycles can be powered by one ATP molecule in intact muscle too, then the current idea that the biochemical processes that release energy from ATP are intimately linked to the mechanical changes in myosin that occur as it produces force will be untenable. In short, we will have to rediscover how muscles convert chemical energy into mechanical energy and find out how that energy can be stored from one force-producing cycle to the next.Read moreRead less
Role Of Nitric Oxide And Reactive Oxygen Species In Excitation-contraction Coupling In Skeletal Muscle.
Funder
National Health and Medical Research Council
Funding Amount
$163,250.00
Summary
Excitation-contraction (E-C) coupling is a term used to broadly describe the sequence of cellular events that starts with an electrical signal at the surface membrane of a muscle cell and which then ultimately leads to muscle contraction. Although the overall sequence is known, there remain many gaps in our understanding of the mechanisms involved not only related to normal muscle function but to how this function may be impaired by excessive exercise and disease. Many cellular metabolites contr ....Excitation-contraction (E-C) coupling is a term used to broadly describe the sequence of cellular events that starts with an electrical signal at the surface membrane of a muscle cell and which then ultimately leads to muscle contraction. Although the overall sequence is known, there remain many gaps in our understanding of the mechanisms involved not only related to normal muscle function but to how this function may be impaired by excessive exercise and disease. Many cellular metabolites contribute towards the normal control of muscle contraction, while others contribute to its impairment. Reactive oxygen species (ROS), which includes nitric oxide (NO) and related molecules, are metabolic factors often referred to as cellular oxidants. They are thought to have an essential role in controlling normal muscle function. Paradoxically, they are also implicated in the impairment of muscle function associated with fatigue, disease and aging. How these molecules both control normal muscle activity and also contribute to impairment of such function remains unclear. Thus, the central aim of this project is to identify the mechanisms by which the cellular oxidants, NO and other ROS, both control normal E-C coupling in skeletal muscle fibres and how they contribute to muscle fatigue. Clearly, understanding how skeletal muscle normally contracts is essential in order to better understand how muscle function can become impaired with exercise, disease and age. The work from this study will provide insight into both normal muscle physiology and how muscles fatigue and ultimately provide new methodologies and drugs that may combat fatigue, disease and age related changes to muscle function.Read moreRead less