In Chinese medicine the lungs are considered responsible in part for giving the body strength. The lungs have always been associated with air and its essential and vital life-giving properties. This breathing exercise is extremely beneficial to the body. It is very quieting to the mind and strengthens the nervous system. It induces a wonderfully calm state, releases nervous tension, anxiety, agitation, anger and other disruptive emotions, and helps you sleep better. It also oxygenates the system, thus aiding in the circulation of energy and blood in the body. This in turn stimulates the proper functioning of all the internal organs. Continued practice of alternate nostril breathing will strengthen the lungs and breath control.
Sit quietly with your back straight either in a chair with your feet on the floor or on the floor with your legs crossed. For those who desire, you may concentrate your attention on the space between the eyebrows while doing this exercise. Begin by gently exhaling all air. Then close the right nostril with the thumb of the right hand and inhale slowly and deeply through the left nostril. When finished, close the left nostril with the ring finger of the right hand, releasing the thumb, and exhale slowly and fully through the right nostril. Next, immediately inhale through the right nostril in a slow and steady manner. Finally, close the right nostril with the right thumb again, releasing the ring finger, and exhale through the left nostril. This completes one round. Begin with ten rounds and gradually increase to forty.
*Source: The Herbs of LIfe: Health & Healing Using Western & Chinese Techniques by Lesley Tierra