Question

Why do we start panting after a long race?​

Answer 1

Answer:

when we exercise, our muscles' need for oxygen leaps upward, and so the blood must deliver more, a lot more, and soon. ... This is the source of panting, huffing, puffing after very strenuous exercise. Every parent will see their child huff and puff and pant after they run hard enough to create such demand.

Answer 2

After much physical exertion, lactic acid builds up in the body as well as carbon dioxide levels. Lactic acid build up can be prevented if the required oxygen flow to the muscles is met. During exercise, our body tends to use more oxygen than we can replenish. Hence after a workout, there is a need to reach our healthy bodily balance (heavy breathing to take in more oxygen).