Nāḍī is the term in Yogic Physiology for a channel or vessel through which prāṇa, energy flows.
You can read more about Nāḍīs here.
While the tradition numbers the nadis in their thousands, the three important ones are the left (iḍā), the right (piṅgala) and the central channel, (suṣumṇā). One of the goals of hatha yoga is to bring prāṇa up the central channel, and to prepare for that ida and pingala need to be brought into balance.
Śodhana means purification, so Nāḍī Śodhana means purifying the Nāḍīs. It is one of the practices yoga developed to bring the Nāḍīs into balance.
Nāḍī Śodhana is a prāṇāyāma practice, the yogic practices which manipulate the breath. (learn more about prāṇāyāma here.)
Pronounce both ṣ and ś as an English sh.
If there is a horizontal bar over the letter it is a long vowel, double the lenght of a short vowel without the bar.
This prāṇāyāma is an alternate nostril breath, so it requires a means to block the nostrils. We do this by means of a hasta mudra or hand gesture.
One way is to curl your rightmiddle and forefinger into the base of the thumb. You then lay the thumb against the right nostril and the ring finger against the left nostril. An alternative is shown in the picture on this page, the middle and forefinger lying on the bridge of the nose instead.
This is the simple version, a competent teacher with expertise in prāṇāyāma may show you more advanced versions.
Close the left nostril with the thumb and inhale through the left.
Gently retain the breath while you open the right and close the left, then exhale out the right.
Inhale through the right.
Gently retain the breath while you open the left and close the right, then exhale through the left.
This is one round.
The breath is gentle and unforced. Continue for up to 5 minutes. Always finish breathing out to the left.
When you finish, sit a while observing the effect this has had in the body and mind.
This is a very calming practice and can be used to settle before meditation or sleep.
By close observation you might have noticed that throughout the day we have either one nostril more clear than the other. It swaps over from time to time during the day. After practising Nāḍī Śodhana, notice that for a while the sides are balanced.
This is a generally safe practice and has lovely benefits. However if any anxiety turns up when doing any yogic breathing practice, cease the practice, or come back to where it was comfortable, easy and anxiety free.
For a small percentage of the population, pressing the nostrils closed on the outside seems to trigger anxiety. In that case, try sealing the nostril by using the thumb or ring finger tip to block the nostril hole.
(Author: Tina Shettigara)