Respuesta :
Basically when doing exercise your body needs way more oxigen because it is using it up faster to be able to do the exercise. While also increasing the breathing rate, the heart rate also goes up because the body needs to pump more blood as the muscles are moving a lot more.
Explanation:
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. 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. When your body runs out of oxygen, or your other systems can't deliver oxygen to your muscles quickly enough, your muscles convert the available glucose into lactic acid instead.