The name alternate nostril breathing is due to the fact that we alternate between the two nostrils when we do the breathing. Yogis believe that this exercise will clean and rejuvenate your vital channels of energy, thus the name nadi sodhana (purification of nadis or channels).

With this exercise, we breathe through only one nostril at a time. The logic behind this exercise is that normal breathing does alternate from one nostril to the other at various times during the day. In a healthy person the breath will alternate between nostrils about every two hours. Because most of us are not in optimum health, this time period varies considerably between people and further reduces our vitality. According to the yogis, when the breath continues to flow in one nostril for more than two hours, as it does with most of us, it will have an adverse effect on our health. If the right nostril is involved, the result is mental and nervous disturbance. If the left nostril is involved, the result is chronic fatigue and reduced brain function. The longer the flow of breath in one nostril, the more serious the illness will be.

1. The exercise produces optimum function to both sides of the brain: that is optimum creativity and optimum logical verbal activity. This also creates a more balanced person, since both halves of the brain are functioning property.
2. The yogis consider this to be the best technique to calm the mind and the nervous system.

Medical science has recently discovered the nasal cycle, something that was known by the yogis thousands of years ago. Scientists have recently found that we don't breathe equally with both nostrils, that one nostril is much easier to breathe through than the other at any particular time and that this alternates about every three hours. The yogis claim that the natural period is every two hours, but we must remember these studies were done on people who do not have an optimum health level.

Scientists also discovered that the nasal cycle corresponds with brain function. The electrical activity of the brain was found to be greater on the side opposite the less congested nostril. The right side of the brain controls creative activity, while the left side controls logical verbal activity. The research showed that when the left nostril was less obstructed, the right side of the brain was predominant. Test subjects were indeed found to do better on creative tests. Similarly when the right nostril was less obstructed the left side of the brain was predominant. Test subjects did better on verbal skills.

Medical science has not quite caught up with the ancient yogis yet. The yogis went one step further. They observed that a lot of disease was due to the nasal cycle being disturbed; that is, if a person breathed for too long through one nostril. To prevent and correct this condition, they developed the alternate nostril breathing technique. This clears any blockage to air flow in the nostrils and reestablishes the natural nasal cycle. For example, the yogis have known for a long time that prolonged breathing through the left nostril only (over a period of years) will produce asthma. They also know that this so-called incurable disease can be easily eliminated by teaching the patient to breathe through the right nostril until the asthma is cured, and then to prevent it recurring by doing the alternate nostril breathing technique. The yogis also believe that diabetes is caused to a large extent by breathing mainly through the right nostril.

1. Close the right nostril with your right thumb and inhale through the left nostril. Do this to the count of four seconds.
2. Immediately close the left nostril with your right ring finger and little finger, and at the same time remove your thumb from the right nostril, and exhale through this nostril. Do this to the count of eight seconds. This completes a half round.
3. Inhale through the right nostril to the count of four seconds. Close the right nostril with your right thumb and exhale through the left nostril to the count of eight seconds. This completes one full round.

Start by doing three rounds, adding one per week until you are doing seven rounds.

Alternate nostril breathing should not be practiced if you have a cold or if your nasal passages are blocked in any way. Forced breathing through the nose may lead to complications. In pranayama it is important to follow this rule: under no circumstances should anything be forced. If you use the nostrils for breath control they must be unobstructed. If they are not, you must practice throat breathing.