If you ever take the time to observe the breath and the manner in which the air flows in and out of the nostrils, you will notice that most of the time respiration takes place through one nostril only. It appears that respiration occurs through both nostrils simultaneously, but this is not so. When you observe the breath, you will find that one nostril usually remains open for a certain duration of time and the breath comes and goes through that side only. Later this nostril closes and the alternate nostril opens.
What does this mean? Physiologically, it has a particular effect on the nervous system, producing a certain type of stimulus. Furthermore, it has a specific influence on the brain which requires very systematic regulation. Swara yoga is the science which reveals this previously unknown process.
Swara yoga explains how the flow of the swara changes at regular intervals; it is not at all erratic. Every hour or every hour and twenty minutes the active nostril changes. This rhythm regulates all the psychological and physiological processes. If the swara is irregular, it is a clear indication that something is not functioning properly in the body.