I hear a few yoga gurus talking about "anuloma viloma" pranayama or breathing technique. What is it and how does it compare with alternate nostril breathing?
We find references to the Anuloma Viloma technique in the Kurma Purana.
I am going to describe the procedure of the practice of Yoga, in order that Yogis may succeed. A wise man should leave his bed in the Usa Kala (i.e., at the peep of dawn or 4 o'clock) in the morning.
Remembering his guru over his head, and his desired deity in his heart, after answering the calls of nature, and cleaning his mouth, he should apply Bhasma (ashes).
In a clean spot, clean room and charming ground, he should spread a soft asana (cloth for sitting on). Having seated on it and remembering in his mind his guru and his god.
Having extolled the place and the time and taking up the vow thus: 'To day by the grace of God, I will perform Pranayamas with asanas for gaining samadhi (trance) and its fruits.' He should salute the infinite Deva, Lord of the Nagas, to insure success in the asanas (postures).
Salutation to the Lord of the Nagas, who is adorned with thousands of heads, set with brilliant jewels (manis), and who has sustained the whole universe, nourishes it, and is infinite. After this he should begin his exercise of asanas and when fatigued, he should practice sava asana. Should there be no fatigue, he should not practice it.
Before Kumbhaka, he should perform Viparita Karni Mudra, in order that he may be able to perform Jalandhar bandha comfortably.
Sipping a little water, he should begin the exercise of Pranayama, after saluting Yogindras, as described in the Kurma Purana, in the words of Siva.
Such as "Saluting Yogindras and their disciples and guru Vinayaka, the Yogi should unite with me with composed mind."
While practicing, he should sit with Siddhasana, and having performed bandhu and Kumbhaka, should begin with 10 Pranayamas the first day, and go on increasing 6 daily.
With composed mind 80 Kumbhakas should be performed at a time; beginning first with the chandra (the left nostril) and then the surya (the right nostril).
11-12. This has been spoken of by wise men as Anuloma and Viloma. Having practiced Surya Bhedan, with Bandhas, the wise man should practice Ujjayi and then Sitkari Sitali, and Bhastrika, he may practice others or not.
- He should practice mudras properly, as instructed by his guru. Then sitting with Padmasana, he should hear anahata nada
So, Anuloma Viloma is basically inhaling first through the left nostril then retaining the breath inside and then finally exhaling the air through your right nostril.
Sometimes, the same practice is done without Kumbhaka (i.e. retaining the breath inside) and then it becomes a good Nadi Suddhi exercise.
If inhalation is done through the right nostril (the Surya Nadi) first then the same Pranayama is called Surya Bhedi and the Anuloma Viloma is called Chandra Vedi.
As I went through this link that explains the alternate nostril breathing, it seems like both are same.
One can say that Alternate nostril breathing, is a westernized term for Anuloma Viloma.
Though some additional practice for Anuloma Viloma also asks the person to focus on the breaths during the process,
that is instead on letting your mind wander to random thoughts observe the air flowing through your nostrils to your lungs and the way out, the same way as done during meditation (in one of the various meditation techniques)