The human body needs more oxygen during exercise because the muscles need to produce more energy for the body to become more active, explains the Lung Institute of Western Australia. This is done by breaking down glucose from food. The LIWA expounds that oxygen is necessary to break down glucose from food. If there is an insufficient amount of oxygen, the body’s muscles will try to produce energy in another way.
However, this often leads to an accumulation of lactic acid, a chemical that causes cramping. Athletes train to make their lungs and muscles more efficient and to delay the buildup of lactic acid. Through exercise, their lungs and muscles are strengthened and are able to work harder. Exercise helps train the body so that more oxygen is carried to the muscles.
During exercise, the body’s muscles send messages to the brain that they require more oxygen, says the LIWA. The brain then transmits signals to the diaphragm and the muscles between the ribs, which are the muscles responsible for controlling breathing, and allows them to shorten and relax more often. This causes a person to take more breaths while exercising. The lungs absorb more oxygen and carry it to the arms, legs and other muscles heavily used during exercise.