You breathe about twenty thousand times a day without deciding to. Your heart beats, your stomach digests, your pupils widen in the dark, and none of it waits for you. Breathing is different. It runs by itself, and the moment you choose to, you can take it over: slow it, deepen it, hold it, send it through one nostril. Almost nothing else in the body gives you that. Pranayama, the breathing practice of classical yoga, is built on it.
What happens when you slow down
An adult at rest breathes roughly twelve to twenty times a minute. Bring that below ten, and in particular to around six, and the heart responds. The heart already speeds up a little on each in-breath and slows on each out-breath, and at this pace the swing grows. The size of that swing, measured as heart-rate variability, is one of the better signs we have that the vagus nerve, the main nerve of the body's rest-and-repair side, is at work.
A 2018 systematic review in Frontiers in Human Neuroscience, by Zaccaro and colleagues, screened more than two thousand studies and kept the fifteen that met its standard, most of them small and in healthy adults. In those, breathing slower than ten breaths a minute raised heart-rate variability and shifted the brain's electrical rhythm towards the alpha waves of relaxed attention. The people breathing slowly reported more comfort, relaxation and alertness, and less anxiety, depression, anger and confusion.
A 2022 meta-analysis in Neuroscience and Biobehavioral Reviews, by Laborde and colleagues, drew on 223 studies and found the same thing from a different angle: the heart-rate variability that the vagus nerve drives rose during slow breathing, was still a little higher just after a single session, and was higher at rest after a course of sessions over weeks. The effect is largest while you breathe, and some of it stays.
Why six
Six breaths a minute is close to the rate at which the breath and the baroreflex, the body's own blood-pressure regulator, fall into step, so that each pushes the heart rate the same way at the same moment. Researchers call it resonance breathing, and it is why so many trials use that pace. The tradition had no instruments and did not count breaths a minute; its texts work by ratio and by holding the breath, and they arrived at a slow, even breath by practice. The Hatha Yoga Pradipika gives pranayama a chapter of its own.
You can find your own rate in a minute. Sit comfortably, set a timer for sixty seconds, and count your out-breaths without changing them. Most people land somewhere in the teens. Now lengthen each breath, with the out-breath longer than the in-breath, and count again. If you reach six or seven, you are at the pace many of the trials used; if you only get to ten, that is enough to begin with.
What it does for mood
In 2023 Guy Fincham and colleagues published, in Scientific Reports, a meta-analysis of randomised controlled trials of breathwork for mental health. For stress, twelve trials with 785 adults showed a small-to-medium reduction compared with controls. For anxiety, twenty trials showed a similar reduction; for depression, eighteen trials showed a slightly larger one. The authors rated the risk of bias in the trials as moderate and asked for larger and better studies. The breath seems to help, measurably but modestly, and the science is young.
Two practices I teach in class
Every classical Hatha class I teach moves from the opening relaxation into two breathing practices before any posture. The first is kapalabhati, a cleansing breath: short, sharp exhalations driven by the abdomen, with the in-breath left to happen by itself. It wakes the body and clears the head. The second is anuloma viloma, alternate-nostril breathing: in through the left, out through the right, in through the right, out through the left, with the breath held between, in a slow count. It is the practice I teach most often.
Both are learned with a teacher. Kapalabhati is set aside in pregnancy, and with high blood pressure, heart disease, a hernia, recent abdominal surgery or epilepsy; the breath retention in anuloma viloma is left out in pregnancy and with high blood pressure too. The pace and the count are built up over weeks, for the same reason you would not learn to swim from a book.
One practice you can do tonight
One slow-breathing practice needs no teacher. It is the one I give to everyone who asks where to start.
Sit or lie down somewhere you will not be interrupted for five minutes. Close your mouth and breathe through your nose. Let the breath go down into the belly rather than the chest; a hand resting on the belly will tell you where it is going. Breathe in for a slow count of four. Breathe out for a slow count of six. Do not force either; if six is too long, make it five. Keep going for five minutes, or for as long as it stays comfortable.
By the third minute your shoulders have usually dropped. The pause at the bottom of the out-breath gets a little longer by itself, and the mind, which was busy, has fewer things to say. Part of that is attention, and part of it is the parasympathetic system taking its larger share. All you did was count.
Two cautions. If you feel dizzy or light-headed, stop and breathe normally; you are probably breathing harder than the practice needs, and it needs no effort at all. And if you are pregnant, have a heart or lung condition, or are being treated for anxiety or depression, tell your doctor what you are doing. The breath is safe for almost everyone, and it is worth knowing if you are one of the exceptions.
The oldest instrument
The Pradipika's second chapter, written six hundred years ago, says that when the breath is unsteady the mind is unsteady, and when the breath is still the mind is still. It is a claim the review in Frontiers would recognise. The tradition had no instrument but the breath itself, slowed down and paid attention to. You have the same one, and it costs nothing.
The Pranayama, Meditation and Deep Relaxation class is where kapalabhati and alternate-nostril breathing get the most time.