The spongy make-up of the lungs does not allow them to be emptied completely - there is always a residue of impure air in the lungs. We must attempt to minimize this "residue" because with the fresh air provided by inhalation it makes up the actual air we breathe.

The more complete the exhalation, therefore, the greater the quantity of fresh air to enter the lungs, and so the purer the air in contact with the alveolar surfaces. The total volume of air which the lungs are able to contain is known as "the vital capacity". A more apt term cannot be imagined, and innumerable techniques have been thought up aimed at increasing this capacity.

Before we can contemplate this improvement we must make use of what we already possess by carefully exhaling. Yoga recognizes three separate forms of breathing - diaphragmatic, intercostal, and clavicular. Complete yogic breathing combines all three, and constitutes the ideal technique.