Adaptation Of Muscle To Eccentric Exercise And Its Clinical Applications 194272
Funder
National Health and Medical Research Council
Funding Amount
$196,410.00
Summary
Work in this laboratory has concentrated on Delayed Onset Muscle Soreness (DOMS), the soreness felt for several days after unaccustomed exercise. This is particularly so when the exercise involves stretching of active muscle, called eccentric exercise, at longer muscle lengths. DOMS is due to microscopic muscle damage. A rapid training effect, leading to reduced soreness from a subsequent bout of similar exercise, has been identified by us as due to a specific structural adaptation. This results ....Work in this laboratory has concentrated on Delayed Onset Muscle Soreness (DOMS), the soreness felt for several days after unaccustomed exercise. This is particularly so when the exercise involves stretching of active muscle, called eccentric exercise, at longer muscle lengths. DOMS is due to microscopic muscle damage. A rapid training effect, leading to reduced soreness from a subsequent bout of similar exercise, has been identified by us as due to a specific structural adaptation. This results in the optimum length for tension generation moving to longer muscle length so that the muscle is less likely to be damaged during subsequent stretches. Hypothesizing that gross muscle tears arise from the microscopic damage, we have begun investigating whether eccentric exercise training can prevent hamstring muscle injuries. We have shown that eccentric exercise shifts the optimum length for contraction in human hamstring muscles. We are now examining athletes with past injuries, known to be likely to re-injure. Other experiments are designed to show that sports that cause injury do indeed include eccentric exercise of the hamstring muscles. We are also investigating the effectiveness of eccentric exercise in treating apparently normal children who compulsively walk on their toes. We have built monitoring equipment and are monitoring both conventional and exercise based treatments designed to shift muscle optimum length to longer lengths to allow the children to place their heels on the ground. Finally, most muscles contain different fibre types, distinguished mainly by their speed of contraction. It has been suggested that they are not all uniformly susceptible to damage from eccentric exercise, a result not predicted by our theory. However, we hypothesize that secondary factors, particularly the length for generating optimum tension, may be responsible for these differences. We plan to test this idea by measuring properties of different types of motor units.Read moreRead less
Signalling Of Muscle Force By Golgi Tendon Organs During Exercise And Fatigue
Funder
National Health and Medical Research Council
Funding Amount
$181,320.00
Summary
It is a common experience for objects being carried to feel heavier and tasks needing muscular effort to become more difficult as one becomes tired and the muscles fatigue during exertion. The sensation of muscle force depends on two factors. One, a sense of the effort required to perform a task, is generated in the central nervous system and. The other, a sense of the force actually developed by the muscles, is generated in the muscles themselves by signals from sensory receptors called Golgi t ....It is a common experience for objects being carried to feel heavier and tasks needing muscular effort to become more difficult as one becomes tired and the muscles fatigue during exertion. The sensation of muscle force depends on two factors. One, a sense of the effort required to perform a task, is generated in the central nervous system and. The other, a sense of the force actually developed by the muscles, is generated in the muscles themselves by signals from sensory receptors called Golgi tendon organs. The sensation of muscle force and the heaviness of objects results from a combination of both senses, but the contribution of each is unknown. The aim of the project is to determine whether the disturbance of force sense in fatigued muscles results from changes in the way tendon organs signal the actual force developed by the muscles. This will be important for understanding how force sense is disturbed following exercise and in disease states, and for understanding the normal way muscle force is sensed in everyday situations. Disturbances of force sense after exercise will be documented in human subjects by asking them to generate what they perceive to be equal forces in both arms or legs, before and after one limb only is exercised. Errors in force estimation will show up as mismatches between the two limbs. The difficulty with human experiments is that the signals generated by tendon organs cannot be measured directly, but only inferred, perhaps wrongly. This difficulty will be overcome by measuring tendon organ activity directly in anaesthetised animals, where the muscles will be electrically stimulated to perform exercise similar to that in the human experiments. A change in tendon organ signalling will be taken to mean that similar changes in humans could be responsible for disturbances of force sense. In further experiments, the mechanism of the changes will be explored.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
Investigation Of The Roles Of Calcium-dependent Proteases In Muscle Damage And Disease
Funder
National Health and Medical Research Council
Funding Amount
$360,160.00
Summary
Muscle strength is important to the health and well-being of everyone. Skeletal muscle weakening occurs as a result of certain disease states, aging and prolonged inactivity due to illness-injury-surgery. This can result in the loss of normal activity and mobility and an increased incidence of falls and accidents, which impact considerably on health care costs. There is a family of proteins called calpains that have been linked to a number of factors affecting muscle function, however it is not ....Muscle strength is important to the health and well-being of everyone. Skeletal muscle weakening occurs as a result of certain disease states, aging and prolonged inactivity due to illness-injury-surgery. This can result in the loss of normal activity and mobility and an increased incidence of falls and accidents, which impact considerably on health care costs. There is a family of proteins called calpains that have been linked to a number of factors affecting muscle function, however it is not known how they are involved. Calpains are proteases, ie. they destroy other proteins, and they are regulated by the concentration of calcium inside a cell. The calcium concentration increases dramatically inside a muscle cell when it contracts. Inside a muscle cell it is important that there is tight regulation of the calpains to avoid them being activated inappropriately during normal use and causing muscle damage. In certain disease states, such as types of muscular dystrophy, it is known that the calcium concentration within resting muscle fibres is increased compared with healthy muscle fibres. We propose that as a consequence of this, the calpains will be less regulated and will cause damage to the muscle, which contributes to the muscle weakness seen in these diseases. Whilst calpains have been implicated with symptoms associated with muscle dystrophies, the role they play is certainly unclear. The objectives of our research proposal are to understand what factors influence i) where the calpains are located and ii) when and how much they are activated, within muscle fibres. We will compare this in healthy muscle and muscle from mdx mice, an animal model of Duchenne muscular dystrophy.Read moreRead less
Does Manipulation Of Arterial Shear Stress Enhance Cerebrovascular Function And Cognition In The Aging Brain?
Funder
National Health and Medical Research Council
Funding Amount
$707,914.00
Summary
Globally, 9.2 million less cases of dementia could result from delaying it by as little as 12 months. We will assess the impact, on artery health and cognition, of a novel exercise intervention involving enhanced patterns of brain blood flow and arterial shear stress during exercise, stimuli which should optimise cerebrovascular health. Given that pharmacological approaches to prevention are ineffective, this project has the potential to address the future impact of this common and debilitating ....Globally, 9.2 million less cases of dementia could result from delaying it by as little as 12 months. We will assess the impact, on artery health and cognition, of a novel exercise intervention involving enhanced patterns of brain blood flow and arterial shear stress during exercise, stimuli which should optimise cerebrovascular health. Given that pharmacological approaches to prevention are ineffective, this project has the potential to address the future impact of this common and debilitating disease in Australians.Read moreRead less