Question: I would like to know why does breathing rate increase whilst doing exercise.

Joanna Barstow answered on 11 Nov 2019:

Breathing rate increases when you exercise because your muscles are working harder, so they need to receive oxygen more quickly. Your breathing speeds up to get more oxygen into your lungs, and your heart rate also speeds up to pump blood around your body more quickly and take the oxygen to where it is needed. If you don’t get enough oxygen to your muscles when you’re exercising, a chemical called lactic acid builds up in them, which can make them feel sore.