How do people breathe in and out?

          We usually don’t have to think much about our breathing because our brain controls it automatically. When you have a lot of carbon dioxide the waste gas produced by body processes in our blood, our brain gets the message and tells our lungs to exhale and get rid of it. This action then causes us to inhale, drawing in air that eventually delivers oxygen to every cell in our body. This carefully regulated exhaling and inhaling takes place about 10 to 14 times each minute when we are breathing calmly.

When we need more oxygen than usual, our brain takes care of that, too. When we are exercising or working hard, our brain tells us to breathe more quickly, taking in 15 to 20 times more air. If that still doesn’t deliver all the oxygen that our muscles need, you may “run out of breath,” which forces you to rest. You will still breathe hard at that point every second or so until your muscles are able to work again.