Your body is surprisingly insensitive to falling levels of oxygen, yet it is very sensitive to increase levels of carbon dioxide. The levels of oxygen in arterial blood vary little, even during exercise, but carbon dioxide levels vary in direct proportion to the level of physical activity. The more intense the exercise, the greater the carbon dioxide concentration in the blood. To combat this, your breathing rate increases to ensure the carbon dioxide can be expelled.
Increased breathing rate
Exercise results in an increase in the rate and depth of breathing. During exercise your muscles demand more oxygen and the corresponding increase increase in carbon dioxide production stimulates faster and deeper breathing. The capillary network surrounding the alveoli expands, increasing blood flow to the lungs and pulmonary diffusion. A minor rise in breathing rate prior to exercise is known as an anticipatory rise. When exercise begins there is an immediate and significant increase in breathing rate, believed to be a result of receptors working in both the muscles and joints.
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It involves two actions: inspiration (an active process), and expiration (a passive process). Breathing is controlled by neural and chemical factors. Increases in the rate and depth of breathing are detected by stretch receptors in the lungs. The respiratory centres of the brain (the medulla and pons) send nerve impulses to the respiratory muscles to control breathing frequently and tidal volume of each breath. When altering depth and rate of breathing, these centres are responding to central and peripheral information. Other information comes from chemoreceptors, such as those in the aortic arch and carotid bodies, which respond to changes in partial pressure. Mechanoreceptors in the joints, tendons and active muscles that assess movement and metabolic status may also feed in