Changes in motor control and kinaesthetic sensations after eccentric exercise.

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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.