What is “Nadi”?
A tubular organ of the subtle body through which energy flows. It consists of three layers, one inside the other, like insulation of an electric wire. The innermost layer is called the ‘sira’ and the middle layer ‘damani’. The entire organ as well as the outer layer is called ‘nadi’.
What is Nadi-Shodhana?
The purification or cleansing of the nadis. Sodhana meaning purifying or cleansing, so the object of Nadi Shodhana Pranayama is the purification of the nerves. A little obstruction in a water pipe can cut off the supply completely. A little obstruction in the nerves can cause great discomfort and paralyse a limb or organ.
1. Empty the lungs completely through the right nostril. Control the aperture of the right nostril with the inner side of the right thumb, away from the nail.
2. Now inhale slowly, steadily and deeply through the right nostril, controlling the aperture with the tip of the right thumb near the nail. Fill the lungs to the brim (puraka). During this inhalation the left nostril is completely blocked by the ring and little fingers.
3. After full inhalation, block the right nostril completely with the pressure of the thumb and release the pressure of the ring and little fingers on the left nostril. Readjust them on the outer edge of the left nostril and keep it parallel to the septum. Exhale slowly, steadily and deeply through the left nostril. Empty the lungs completely. The pressure should be exerted from the inner sides of the tips of the ring and little fingers (away from the nails) (rechaka).
4. After full exhalation through . the left nostril, change the pressure on it by adjusting the fingers. In the changed position, the tips of the ring and little fingers nearer the nails exert the pressure.
5. Now inhale through the left nostril slowly, steadily and deeply, filling the lungs to the brim (puraka).
6. After full inhalation through the left nostril, block it and exhale through the right nostril, adjusting the pressure of the right thumb on the right nostril.
7. This completes one cycle of Nadi Shodhana Pranayama.
Inhalation and exhalation from each side should take the same time. In the beginning the duration will be unequal. Persevere until equality is achieved.
After achieving mastery over the equal duration and precision over inhalation and exhalation on either side an attempt may be made to retain’ breath (antara kumbhaka) after inhaling. This precision is only achieved after long practice.
Retention should not disturb the rhythm and equality of inhalation and exhalation. If either are disturbed curtail the period of retention or hold the breath on alternate cycles.
Do not attempt to hold the breath after exhalation (bahya kumbhaka) until you have mastered retention after inhalation (antara kumbhaka).
Retention and the lengthening of inhalation and exhalation should only be attempted with the help and under the guidance of an experienced Guru.
Always conclude by lying down in Savasana.
The blood receives a larger supply of oxygen in Nadi Shodhana than in normal breathing, so that one feels refreshed and the nerves are calmed and purified. The mind becomes still and lucid.
In the beginning the body perspires and shakes, while the thigh and arm muscles become tense. Such tension should be avoided.Persons suffering from high blood pressure or heart trouble should never attempt to hold their breath (kumbhaka). They can practise Nadi Shodhana Pranayama without retention (kumbhaka) with beneficial effect. Persons suffering from low blood pressure can do this praJ:layama with retention after inhalation (antara kumbhaka) only, with beneficial effects.
Ref: The Illustrated Light on Yoga by BKS Iyengar