Question

Why does breathing rate need to rise during exercise? Explain as fully as
possible. Why does the rate not return to normal as soon as a subject
finishes the exercise?

Answer 1

These processes require oxygen. This is why, when the period of activity is over, a person's breathing rate and heart rate do not return to normal straightaway. The amount of oxygen required to remove the lactic acid, and replace the body's reserves of oxygen, is called the oxygen debt.

Answer 2

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.