Btec Sport
Assesment 2
Fibre types
There are three twitch fibres. Slow oxidative fibres, fast oxidative glycolytic fibres and fast glycolytic fibres. Our skeletal muscles contain a mixture of all three types of fibres but not in equal proportions. This is mainly genetically pre- determined but training can also influence the effectiveness of fibre types.
Our skeletal muscles contain a mixture of all three types of fibres but not in equal proportions. This is mainly genetically pre- determined.
Slow Twitch Fibres (type 1)
Slow twitch fibres use oxygen to generate more energy. They are more suited to aerobic work as they have a rich blood supply and contain a lot of mitochondria and myoglobin. They have more blood capillaries than fast twitch fibres. They are red in colour due to the large amounts of myoglobin, Due to this fact they are very resistant to fatigue.
Slow twitch fibres do not contract with as much force as fast twitch fibres but can cope with prolonged exercise. They have the enzymes necessary for aerobic respiration and are able to break down fat and carbohydrate to water and carbon dioxide. Slow twitch fibres are used for lower- intensity, longer duration activities such as long distance rowing and skiing. This is where you can last for 2minutes or more and keep the same pace.
Fast Oxidative Glycolytic Fibres (type2a)
Fast oxidative glycolytic can produce energy both anaerobic and aerobically. The rapid build up of lactic acid lowers the pH which has a negative affect on enzyme action. This means they are fast contracting and able to produce an enormous force but still can be resistant to fatigue. These fibres are suited to middle distance events such as 800m as type 2a exerts a medium force.
Fast Glycolytic Fibres (type 2b)
These fibres contract very hastily and construct a lot of force. They are very high intensity and are pure anaerobic. The nerve cells are much bigger which sends faster and more powerful messages. Fast glycolytic fibres have far less capillaries, mitochondria and myoglobin than slow twitch fibres. This means they can only work at a high intensity for 10 seconds or less, which means you need to have a lot more rest than a slow twitch fibre. These are important in sports for shot put and 100 metres sprinting.
A good games player would need an equal of all three muscle fibres. This is because at different points in a game you need to use different types of fibres due to the intensity you work at. For example in football when you are sprinting with the ball or trying to beat an opponents to the ball you would use type 2b, as you use great force and your contraction speed is rapid. You become fatigued very quickly but use a lot of speed, strength and a lot of force. You would then need type 1 as you would need a lot of endurance so you are able to last the whole game with out becoming fatigued quickly. You would then use type 2a if you are trying to tackle your opponents for the ball. This is because you will be contracting rapidly but not as fast as type 2b and you would be working at medium force at a longer period than type 2b but a shorter period than
type 1.
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