“The body can go for many weeks without food and for days without water or sleep, but life will cease in a matter of minutes without air. Thus, the primary element of life is derived from the air we breathe. In yoga, this subtle element is known as prana or life-force. Prana is not the air itself but the subtle life-giving element extracted from the air. The more life-force you have in your body, the more “alive” you are; the less life-force, the less “life”. Life-force is present in all forms of nourishment but it is accessible and most constant in the air.
Even though no one can live for more than a few minutes without breathing, most people are unaware of the importance of breathing properly. Most people use only a fraction of their full breathing capacity. A combination of stress, poor posture, long hours behind desks, and flat-stomach phobia turns many people into “chest breathers” – people who expand only the upper chest when they inhale. Chest breathing creates an imbalance in the oxygen/carbon dioxide ratio, which results in hyperventilation and dizziness.
For optimal health, breathing should be full and rhythmic using the diaphragm and ribs to fill and empty the lungs. Proper breathing is governed primarily by the movement of the diaphragm. As it descends, the abdomen expands drawing fresh air in through the nose and into the lungs. Deep abdominal breathing promotes a full exchange of air, keeping the oxygen/carbon dioxide ratio balanced. Proper breathing can tone up your entire system and enhance health and vitality.”
To learn more about breathing, check out Edith Howell’s page – http://www.yogaforbeginners.com/breathing01.htm