When you exercise and your muscles work harder, your body uses more oxygen and produces more carbon dioxide. To cope with this extra demand, your breathing has to increase from about 15 times a minute (12 litres of air) when you are resting, up to about 40–60 times a minute (100 litres of air) during exercise.

What happens in the respiratory system during exercise?

During exercise there is an increase in physical activity and muscle cells respire more than they do when the body is at rest. The heart rate increases during exercise. The rate and depth of breathing increases - this makes sure that more oxygen is absorbed into the blood, and more carbon dioxide is removed from it.

How does the respiratory system work when running?

1. The endurance capacity of your respiratory muscles – including the diaphragm and intercostal muscles – increases, allowing deeper, fuller and more efficient breaths when you run. 2. With regular training you grow more capillaries, which means you can get more oxygen to your muscles quicker.