Question

why does the breathing rate change during physical activities like running or cycling?​

Answer 1

Answer:

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.

Answer 2

Answer:

while cycling or running your muscles work

harder so more oxygen is needed to provide more energy to the muscles and to remove carbon dioxide which is released as waste product when energy is released so lungs pump harder to take in more oxygen which causes change in breathing rate