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Topic last updated: 24 Nov 2021
    • Ico Chemistry Chemistry
    • Ico Physics Physics
    • Ico Science Science
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Materials and their properties

When you are asleep or sitting quietly, you move about 500 cm3 of air in and out of your lungs between 12 and 14 times a minute. This is called resting breathing. It supplies the oxygen needed for the cells of your body to grow, for the muscles which keep you upright, for your heart and gut muscles and all the other processes which take place whether you are awake or asleep.

However, as soon as you start to do things the oxygen demand of your body cells increases. Your breathing changes to meet those demands. You can get more oxygen into your body – and get rid of more carbon dioxide – both by breathing more deeply and by breathing faster. Often you do both!

It isn’t only exercise that affects your breathing rate – stress and anxiety, drugs, being overweight and changes in the environment can all change the rate at which you breathe.


Exercise and fitness

When you exercise, the muscle cells which move your skeleton contract harder and faster than when you are still. As a result they need more oxygen to break down glucose and supply the energy they need by aerobic respiration. They also produce more carbon dioxide which has to be removed to keep your muscles working effectively. Your breathing rate goes up. You breathe more deeply so the volume of air you take in with each breath goes up too.

If you exercise really hard you can’t get enough oxygen and your muscle cells respire anaerobically. This means that even after you stop exercising you still need more oxygen that usual to make sure that the lactic acid produced during anaerobic respiration is completely broken down to give carbon dioxide and water. This is why you continue to puff and pant even when you have stopped exercising hard.

If you exercise regularly, you get fitter. Your lungs get bigger and develop a better blood supply. This means you breathe more efficiently. A fit person will have a slower resting breathing rate than an unfit person, and they will recover more quickly after exercise.


The change in breathing rate during and after exercise in a fit person and an unfit person

The change in breathing rate during and after exercise in a fit person and an unfit person


Even though this man is fit, he still breathes faster and more heavily during and after exercise. (Photo credit: Anthony Short)