A muscle has a body and a tail which is the tendon. The tendon is an extension of the muscle and is usually attached onto a bone to assist in raising and lowering of a limb. Muscles act like small motors that move every part of the body. Each muscle is activated by a nerve which relays the messages from the brain to affect every single function in the body.
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Proteins - These are never a source of immediate energy and are a poor substitute of energy during exercises. Proteins are a building block for the tissues in the body. The body has no way to store extra protein.
Fats - A secondary source of energy especially during the later stages of sports. Fat is stored in the muscles, under the skin and around the inner organs.
Carbohydrates - The primary fuel for exercise. Your body can store carbohydrates in muscles and the liver in the form of glycogen. Glycogen and fat are the main fuel the muscles burn up for energy.
To burn these fuels efficiently, oxygen is needed and this is delivered to the muscles through the bloodstream by the red blood cells. This is the reason for the importance of muscle toning. The toned muscles have larger blood vessels, allowing more blood to flow through them, hence taking in more oxygen to the muscles for them to burn glycogen and fats.
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By training properly you can improve your oxygen utilisation. In so doing you are improving the ability of the the heart to push more blood to the muscles and you are improving the ability of the muscles to extract the oxygen from the bloodstream. Training will strengthen your heart so that it has the capacity to pump a greater volume of blood to each heart beat, enlarge your arteries and blood vessels so more blood can flow through them, increase the number of your red blood cells so that your oxygen-carrying capacity is increased and increase the rate at which the enzymes in your muscles pick up the oxygen from the bloodstream.
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Loss of muscle glycogen - the primary fuel of muscles.
Loss of fat reserves - a secondary fuel of muscles.
Low level of blood sugar - called hypoglycemia
Lack of oxygen
Heat build up in the muscles (Hypothermia)
Accumulation of lactic acid - a break down product of exercising without oxygen. When glycogen is burned up it is broken down into a chemical called pyruvate. If there is enough oxygen available, pyruvate converts it into carbon dioxide and water, which are blown off from the lungs. However, if there is not enough oxygen in the muscles, pyruvate converts it into lactic acid, which builds up in the muscles and then overflows into the bloodstream. Lactic acid impedes muscle contractions and make it difficult for muscles to move. As a result, you can feel fatigued. A high level of lactic acid will eventually stop the muscle from contracting altogether. When this happens you lose all control over the muscles and they become very painful and may cramp. As soon as oxygen becomes available again, lactic acid converts back to pyruvate and to carbon dioxide and water and the sports person has a feeling of a new lease of life.
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