Swara Yoga ~ Tantric Science of Brain Breathing.
Swara Yoga is the study of the breath in great detail and of the pranic rhythms in the body. It is related to the Tattwas (elements within body and space), Nadis (channels carrying energy within the body), Koshas (The sheaths or fields of the body, starting from the gross food body and moving all the way out to the subtle bliss body). Our breathing changes every 90 minutes or so throughout the day, going from being primarily flowing through one nostril or the other, and then briefly for a cross-over time, it flows smoothly through both. Different activities such as eating, physical work, sex, buying, studying, travelling etc are favoured if practised while the breath flows in the beneficial nostril for that task. And it is said that the brief time when the breath flows evenly in both (which corresponds to Sushumna flowing) is the perfect time for either activities of great good (such as meditating) or great evil (such as murder!)
Most diseases of the body and mind arise first as an imbalance in the Swara. For example you may notice that one nostril feels blocked over some days and later you may come down with a flu, but more seriously if a nostril predominates constantly over the other then you may experience serious depression or anxiety. I experienced severe anxiety for a long time and the attacks always took place while the Swara was flowing in my right nostril, which influences the left side of the brain, that is the Sympathetic nervous system, so I often had to block the right nostril if I could not go somewhere and rest to try and make the Swara flow in the left nostril, thus stimulating the right side of brain and the Para-sympathetic nervous system. It did help, but long term one needs to balance the Swara more effectively.
I find the literature on Swara Yoga to be a little bit occultish, in the sense that it includes instructions on how to tell time of death, or approach maleficent activities, and so on, but there are also many interesting aspects which are completely applicable in everyday life, and which become automatic when you know them.
For example, to approach people in authority, your Bank manager or a difficult bureaucrat for example, or to have a better chance of influencing somebody, approach them from the side your active Swara is flowing.
If you feel a headache coming on check immediately which side the Swara is predominant on (hand below nostrils or block and sniff and see which one is more open) and then lie down on the same side as the flowing nostril. This compresses the armpit which causes the nostrils to gradually switch over a few minutes, and the blocked ''upper'' nostril will now flow and 9 times out of 10 the headache will be averted. Particularly good for migraines. Can be used for any disease, but we are not always sensitive to the onset of illness and so do not ''catch'' the Swara in time to change it. Predominant Ida (left nostril) tends to relate to congestive conditions, mucus problems, colds etc. And predominant Pingala (right nostril) to fever conditions.
Likewise it is advised for example that the left side is the best side to sleep on as this encourages the Swara to flow in the right nostril. Now to me that does not make absolute sense as right side is Sympathetic, but anyways that is the advice given, and I generally find sleep on the left side to be most refreshing. Perhaps it is because when the right nostril flows the pranic energy is stronger and the mental energy is weaker, which allows the prana to refresh the body, while the mind is more restful.
Note that yogis often make use of Dandas or wooden sticks or crutches which they place under one of their armpits. This slight compression causes the Swara to flow in the opposite nostril, a choice they will be making for whatever reason, depending on circumstance. The same effect can be got by squeezing your hand under your armpit for a period of time. If necessary one can plug up the nostril with a cotton plug.
In Shiva Swarodaya, the scripture it says that Swara yoga is related to the planetary movements. Study of these without knowledge of Swara is said to be useless. Ida and Pingala within the human body synchronise themselves to lunar/solar rhythms. Left Nostril flowing is Ida, right is Pingala. Left is Lunar, Right solar.
''One hemisphere remains active for 60-90 minutes, when the cycle is complete there is a transfer of energy through a thin sheet of membrane called the Corpus Callosum, which conducts the energy from one hemisphere to the other over the course of 1-4 minutes.''
There are many practices which are included in the book, so I won't go into them...you can research them if you are interested, but one that is interesting is using a glass mirror beneath the nostrils and telling form the shape of the breath on the glass (or the length of the breath as it travels away from the nostrils) which Tattwa is predominating in the body at the time. Another related practice is shadow gazing, watching your own shadow intently with the sun at your back and then noticing afterwards which colours pass in the space behind the closed eyes ~ this is another way for deciding which Tattwa predominates. (Note Earth = Yellow, Water = White, Fire = Red, Air = Blue and Ether = Silver/Grey)
Harish Johari also mentions in his books that knowledge of Swara is important for Ayurveda. For example if the left nostril predominates then the body is predominantly alkaline and if it is right predominant then it is acidic. Right nostril flowing should not be used for meditation according to him. Or for drinking or urination. In fact eating and bathing are also better done when Left predominates. He advises that unless a right nostril flow is required for specific activity we encourage left nostril most during the day, as this is cooling when we are under the influence of the solar energies, and vice versa for night.
That's about it from me. All errors here are my own and not my teachers. Research further yourself if interested.
OM TAT SAT