What happens to the rate of breathing during vigorous exercise and why?

The breathing rate increases therefore the depth of breathing increases. During a vigorous exercise we undergo anaerobic respiration in muscles when there is not enough oxygen reaching to the cells to convert glucose into water and carbon dioxide (the products of anaerobic respiration with the presence of oxygen). During anaerobic respiration, glucose is only partially broken down into lactic acids and a relatively small amount of energy. Accumulation of lactic acids in the muscles causes pain and discomfort and may lead to muscle fatigue which is when the muscles are not able to contract properly. The muscles must rest and recover. Accumulation of high levels of lactic acids in muscles is toxic and must be removed. During the rest period, lactic acid is removed by the circulatory system to the liver. In the liver, lactic acid is oxidized to produce energy. This energy is used to convert the remaining lactic acids into glucose and eventually glycogen to be stored in the liver. This only happens after the period of anaerobic exercise has ended. The amount of extra oxygen that the body takes in after an exercise to convert the lactic acids into glucose is called the oxygen debt. This explains why we continue to breathe heavily,deeply and quickly after exercising. Hope this helps! -AA