physioligy of fitness

bodies response to acute exersize

musculoskeletal responses

Increase in blood supply:

during excersize there is an increase of blood flow to the muscles, this is because of the increased demand of oxygen from the muscles

Increase in muscle pliability:

during the excersize the muscle gets warmer and so becomes more pliable. This reduces the risk of injury.

Increased range of movement:

during excersize there is and increased production of synovial fluid into the joints. The fluid becomes more liquid and the range of movements at a joint increase. This synovial fluid becomes a lubricant for the joints to stop them rubbing against each other.

Muscle fibre micro tears:

during excersize your muscle fibres get micro tears and releases chemicals that cause soreness. These chemicals also stimulate muscle growth and repair increasing muscle mass.

energy system responses


phosphocreatine is a high energy compound when enrgy requirement is high or is needed instantaneously. Phosphocreatine in the muscles is broken down which provides energy to make ATP. This energy system lasts for about 5-8 seconds, so it doesnt last as long as the other systems. It is most suited to short distance activities such as the 100m sprint and it takes about 2 minutes to recover.

Lactic acid:

This system is used after the ATP system has ran out of energy. lactic acid is created in the body when we dont have enough oxygen to make energy the usual way. What happens is the bodys glucose is broken down and the energy from the reaction is used. However a byproduct of this is lactic acid and it doesnt provide as much energy as the normal reaction does. The system is used for about 60-90 seconds and depending on the intensity of the exersize can take between 30 minutes to 2hours to recover. The lactic acid produced in this energy systmes are problematic becuase it can cause cramp, nausea etc.

Aerobic system:

the aerobic system is used when we are excersizing without oxygen this normally happens about a minute and a half after we start,excersizing depending on intensity. What the aerobic system does is it provides ATP at a slower rate. The body breaks down the bodys glucose but this time with oxygen so it doesn't create lactic acid. This system in theory can last as long as you want as long as the level of exersize isnt too high and the breathing is constant. This means that this system is suited to low level exersize that is long distance

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cardiovascular responses

Heart rate anticipatory response:

during excersize due to the oxygen demand the heart rate increases. Even before you start to excersize your heart rate begins to increase this is the anticipatory rise. This happens because when you think about excersizing your body releases adrenaline which increases your heart rate. More adrenaline is later released during excersize.

Activity response:

During the excersize the body uses oxygen to create energy so during excersize the heart rate will increase. This is because the muscles need the oxygen to break down the glucose to create the energy. The body releases energy during excersize to increase the heart rate so that the oxygen intake increases.

Blood pressure:

Blood pressure is what forces the blood around our body this is created by our hearts contractions. As previously discussed the heart rate increases during excersize. This means that there are more contractions of the heart meaning blood pressure goes up

Vaoconstriction and vasodilation:

the blood flow will increase during excersize this happens by the body diluting the blood vessels this is known as vasodilation. This happens so that the blood can flow to the muscles/organs that need the blood. Vasoconstriction is the constriction of the blood vessels to the tissue this can make you turn paler. This is once again the body delivering the blood to the parts of the body which need it mist which during excersize is the muscles.

respiratory responses

Increase in breathing rate:

when the body uses oxygen to create energy this creates carbon dioxide which is harmful to our body. By increasing our breathing rate not only do we increase our oxygen intake but we also exhale the harmful carbon dioxide. This is why our breathing rate increases during excersize

Increase in tidal volume:

The amount of air which our body breathes in is known as the tidal volume. This increases during excersize to allow more oxygen to pass through the lungs to be used to create energy

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