Physiologists claim that the air breathed in should remain in the lungs for ten to twenty seconds to maximize the gaseous interchange in the lungs. The yoga practitioners devised an exercise in which the breath is retained for four times the duration of inhalation (about twelve to sixteen seconds) thousands of years ago. Yogis and pranayama followers claim that this exercise would take maximum advantage of the air inhaled.

1. It provides the optimum supply of oxygen to the body. Even jogging and other aerobic exercise doesn't achieve this, since the breathing is quick and shallow and there is no retention of oxygen.
2. The air which has remained in the lungs from previous inhalations is purified.
3. There is increased oxygenation of the blood.
4. The retained breath gathers up some of the waste matter of the body and expels it on exhalation.
5. The lungs increase their elasticity and capacity and become more powerful. This allows benefits to be enjoyed all day, not just during the exercise.
6. The exercise builds a bigger, more powerful chest and prevent, or helps to correct sagging breasts in women.

1. Sit up straight.
2. Inhale for four seconds. Push your stomach forwards to a count of two seconds and then push your ribs sideways for one second, and finally lift your chest and collar bone upwards for one second. This makes a total of four seconds.
3. Hold the breath for sixteen seconds. If you find this is difficult at the start, just hold for eight seconds, and gradually over a period of a few months build up to sixteen seconds.
4. Exhale for eight seconds. For the first six seconds, just allow the collar bone and ribs to relax, so the breath goes out automatically. For the last two seconds push the stomach in gently to expel the air from the lungs.

Do this exercise only once the first week, and add one more round each week, until you are doing three rounds.

The yogi rule for the retention breath is that exhalation should be twice that of inhalation, and retention should be four times that of inhalation; that is, a ratio of 1:4:2.