Breathing is the act of moving air in and out of your lungs, as the diaphragm muscles moves up and down in the chest. Breathing in is called inhalation. Breathing out is called exhalation.

During vigorous exercise the rate of breathing increases than the normal rate because more oxygen is needed for more energy and carbon dioxide produced in the respiratory cells of the muscles. The increased production of carbon dioxide increases the rate of breathing and thus oxygen is quickly supplied to the body cells and carbon dioxide is rapidly removed from lungs.