The vocabulary
The six that work on the breath
Nāḍī Śodhana
alternate nostril
What you do
In through one nostril, out through the other, closing each in turn with the fingers. The pace is slow and the two sides are kept even.
In Western terms
Slow, evenly paced breathing. Breathing at this rate, and alternate-nostril breathing in particular, is associated with reduced sympathetic arousal: less of the roused side, more of the resting side.
Ujjāyī
the ocean breath
What you do
A slight narrowing at the back of the throat, so the breath is audible to you and nobody else. It comes out slower than it went in, and the sound is what you pace it by.
In Western terms
The out-breath ends up longer than the in-breath. A longer exhale raises vagal tone and shifts the balance toward parasympathetic activity, which is what “calming” means here.
Kapālabhāti
skull shining
What you do
Short sharp exhales driven from the belly, the in-breath left to happen by itself. Done in rounds of a fixed count, with ordinary breathing between them.
In Western terms
Rapid, forced breathing is stimulating rather than calming. It raises arousal, which is why it belongs in short rounds followed by stillness, not at the point where you are trying to settle.
Bhastrikā
the bellows
What you do
Forceful both ways at the same speed, the whole breath driven rather than half of it. Also done in short rounds, never run on.
In Western terms
Stimulating rather than calming, for the same reason: fast, effortful breathing raises arousal. Whatever settling follows comes from the pause after a round, not from the round.
Ānāpāna
breath awareness
What you do
Nothing about the breath is changed. Attention rests where the breath can be felt, and when it wanders it is brought back. That is the entire instruction.
In Western terms
Attention training rather than a breathing exercise. The breath is watched, not altered, so there is no physiological claim to make about it.
So’ham / Ajapa
the syllable on the breath
What you do
A syllable carried silently on the breath: so on the way in, ham on the way out, with no effort to force either. It counts as japa that repeats itself.
In Western terms
Pairing a syllable with the breath tends to keep it slow and even. Anything physiological that follows is what slow, even breathing does; the syllable is the metronome, not the mechanism.
Being guided, and by what
Nothing tells you when to breathe
There is no pacer, no metronome and no voice counting you through it. What is on screen is a readout of you.
The clock only counts up
No target length, no countdown, no streak to keep. A fresh reading lands about every four seconds, and the timer runs until you end it.
Delve follows rather than leads. What a timer does not give you is something reading for the whole sitting: a state reading every few seconds, your pulse, and how still you sat. Choosing a practice labels the record; no part of the analysis branches on it.
What is not claimed: none of these are treatments, and nothing here is medical advice. Delve does not measure what a practice does to your nervous system. The physiology under each name is the ordinary, settled account of slow and rapid breathing.