Prāṇāyāma — breath practice, described accurately

What it is for

In Patañjali's scheme, prāṇāyāma sits fourth, after posture and before the withdrawal of the senses. Its stated function is to remove what obscures clarity and make the mind fit for concentration.

That is worth holding onto, because most contemporary teaching presents it as a relaxation technique. Calm is a common effect. It is not what the text says the practice is for, and several of the classical techniques are stimulating rather than calming.

The main techniques

Nāḍī śodhana — alternate nostril. Inhale through one nostril, exhale through the other, alternating. The standard beginning practice, low-risk without retention, and the one most widely taught.

Ujjāyī — a slight constriction at the throat producing an audible breath, used to lengthen and smooth the cycle. Familiar to anyone who has done a vinyasa class.

Bhrāmarī — the humming breath, exhaling with a bee-like sound and the ears closed. Reliably settling, and safe.

Kapālabhāti — sharp forceful exhalations with passive inhalation. Vigorous; classified in the older texts as a cleansing practice rather than as prāṇāyāma proper.

Bhastrikā — bellows breath, forceful in both directions. The most demanding of the common practices and the one most often taught carelessly.

Śītalī and śītkārī — cooling breaths drawn over the tongue.

Kumbhaka — retention, after inhalation or exhalation. This is where the classical literature places the real work of prāṇāyāma, and also where it places its warnings.

What the research supports

Slow-breathing practices — roughly six breaths a minute — have been studied reasonably well and show short-term effects on heart-rate variability, blood pressure and self-reported anxiety. Effects tend to be modest and the studies are usually small.

Beyond that, the picture thins quickly. Trials of specific techniques for specific conditions are mostly small, short and of variable quality, and the literature has the same positive-result bias found across yoga research.

What is not supported by that literature — and is often asserted — is that particular techniques detoxify, oxygenate the blood beyond normal levels, or alter the course of serious disease.

The safety section that classes skip

The haṭha texts themselves are blunt about this: practised wrongly, they say, prāṇāyāma causes illness, and a teacher is necessary.

In modern terms, the specific cautions are:

• Forceful practices and retention in uncontrolled high blood pressure, glaucoma or retinal disease, epilepsy, and pregnancy.
• Hyperventilation techniques can cause dizziness, tetany and fainting — practise seated, never standing, and never in water.
• Recent surgery to the abdomen or chest, and active respiratory infection.
• Intensive practice can surface anxiety and dissociation in susceptible people, which is documented in the meditation literature and applies here too.

None of that is a reason not to practise. It is a reason to start with the mild techniques, to build slowly, and to treat "more is better" as the error it is.

How this changes across traditions