Naadi Shuddhi pranayama is a singularly important pranayama for bringing the balance - between both nervous systems - parasympathetic and sympathetic nervous systems; by the practice of naadi shodhan pranayama, the pranic channels are purified and the proper flow of pranic energy throughout the body is enhanced. Alternating the inhalation and exhalation is done during this pranayama between the left and right nostrils. Naadi Shuddi pranayama is truly a balanceing pranayama as it corrects the imbalance both in mental and physical body and restores equilibrium therebetween.
In Hatha Yoga Pradipika, the process of naadi shuddhi pranayama is mentioned as follows:
Baddhapadmasano yogi pranam chandrena puryaet,
dharayitva yathasakti bhuyah suryena recayet,
Pranam suryena cakrsya purayedudaram snaih,
Vidhivatkumbhakam krtva punascandrena recayte
Which means - sitting in padamasana, the yogi inhales through the left nostril, holds the breath as per one's capacity, exhales through the right nostril, and inhales through right nostril after performing kumbhaka (retention of breath) exhales through the left.
Explanation:
Inhale through the left nostril by closing the right nostril with the thumb in nasika mudra.
You can retain the breath as per the capacity.
Open the right nostril and close the left with the ring finger and little finger to exhale slowly through the right nostril.
Again retain breath as per the capacity.
slowly inhale through the right nostril.
Again retain breath as per the capacity.
Open the left nostril and close right nostril through the thumb of the right hand (in nasika mudra) and exhale through the left nostril.
Again retain breath as per the capacity.
This completes one round of naadi shuddhi pranayama. May you can complete 6-8 rounds.
The retention of breath should be enjoyable and should not be beyond one's capacity otherwise it may harm your respiratory system and cause damage.
The pranayama should be learnt by some qualified yoga practitioner