What counts as slow breathing
At rest, a person typically breathes 10 to 20 times a minute. A 2017 review of the physiology of slow breathing, by Russo, Santarelli and O'Rourke, defines slow as anything from 4 to 10 breaths a minute. Another review, by Zaccaro and colleagues in 2018, uses a similar cutoff: 10 or fewer.
Most studies zero in on one spot: about six breaths a minute, or ten seconds per breath. That's the pace of Coherent breathing 5-5.
Bigger breaths
Your body needs to move roughly the same amount of air each minute. If you take fewer breaths, each one has to be larger. The 2017 review notes that slow breathing generally comes with more volume per breath and may increase how far the diaphragm travels.
That has a practical upshot. With every breath, some of the air stays in your windpipe and bronchi and never reaches the place where oxygen is exchanged. With bigger, less frequent breaths, that share matters less. One study cited in the review found that six breaths a minute was the pace that ventilated the air sacs best.
Your heart follows your breath
Your pulse isn't steady like a metronome. It speeds up a little when you breathe in and slows down when you breathe out. That back-and-forth has a long name: respiratory sinus arrhythmia. Despite the name, it's a normal heart pattern.
When you breathe slowly, the swing gets bigger. The 2017 review says it peaks at around six breaths a minute, something numerous studies have confirmed. Because your pulse changes more from one beat to the next, heart rate variability goes up too, a measure that shows up in nearly every study on the subject.
The baroreflex and resonance frequency
Your aorta and carotid arteries have sensors that detect how much the vessel walls stretch with each change in pressure. When pressure rises, your heart slows down right away. When it falls, your heart speeds up. That automatic adjustment is called the baroreflex.
The baroreflex has a rhythm of its own, close to one cycle every ten seconds. Paul Lehrer and Richard Gevirtz explain that if you breathe at that same pace, the two oscillations add up and the swing in your pulse is amplified. They call that point the resonance frequency.
It isn't the same for everyone. It hovers around six breaths a minute, with an average closer to five and a half, and it tends to be lower in taller people. That's why the site has both Coherent breathing 5-5 and Resonant breathing 5.5-5.5: two starting points, not an exact measurement of your body.
As for blood pressure, the 2017 review reports that its oscillations grow and that several studies measured lower average pressure during controlled slow breathing. Those readings were taken while people were breathing that way. They don't say what happens afterward.
What people feel and what studies measure
Zaccaro's 2018 systematic review pulled together 15 studies of healthy adults. Taken together, they found higher heart rate variability and changes in the brain's electrical activity, with more alpha waves and fewer theta waves. Some reported more comfort, relaxation and alertness, and less anxiety, anger and confusion.
The limits matter. There were few studies, and their techniques differed widely. None was a randomized trial or followed people over time. Many found no clear psychological effects. And all of them involved healthy people, so they say nothing about illness. The authors describe the evidence as interesting but limited.
What isn't known yet
- Exactly why it happens. The authors of the 2017 review write that the mechanisms are still under debate.
- The role of the vagus nerve. Lehrer and Gevirtz suggest that signals traveling up it to the brain might explain part of the effect on mood. They present that as speculation themselves.
- What sustained practice leaves behind. There are few measurements of people who practice for months or years.
- Whether findings in healthy people carry over to the clinic. That's studied separately, with other methods, and it's a health professional's call.
How to try it gently
If six a minute feels far off, start with 4-6 breathing, which also runs at six a minute but with a shorter inhale. Then try coherent breathing 5-5 for five minutes and notice how you feel when you finish. 5-5-2 breathing adds a brief two-second rest and drops to five a minute.
Breathe slow, not huge. If you feel dizzy or tingly, stop and go back to your normal pace. And if you have a heart, lung or blood pressure condition, check with your care provider first.
Frequently asked questions
How many breaths per minute is normal?
At rest, adults typically take 10 to 20 breaths a minute. Studies call it slow breathing when the rate drops below 10. You don't need to breathe that way all day: it's a practice that lasts a few minutes.
Why does everyone talk about six breaths per minute?
Because near that pace, the swing in your pulse as you breathe reaches its peak in most people. The exact point varies from person to person, with an average close to five and a half. It's a reference, not a required target.
Does slow breathing lower blood pressure?
Several studies measured lower average pressure while people were breathing slowly. That doesn't make it a treatment. If you have high blood pressure or take medication, check with your care provider before changing anything.
What is heart rate variability?
It's how much the time between one heartbeat and the next changes. It goes up when you breathe slowly, because your pulse rises on the inhale and falls on the exhale over a wider range. Studies use it as a sign of how the heart is regulated, not as a health score.
Sources
- Russo, Santarelli and O'Rourke 2017, The physiological effects of slow breathing in the healthy human, Breathe
- Zaccaro et al. 2018, How Breath-Control Can Change Your Life: A Systematic Review on Psycho-Physiological Correlates of Slow Breathing, Frontiers in Human Neuroscience
- Lehrer and Gevirtz 2014, Heart rate variability biofeedback: how and why does it work?, Frontiers in Psychology