Four books cover the ground this site works from. Short reviews, what each one is good for, and where it is thin. Links go to Amazon; if you buy through them we earn a small commission at no extra cost to you, which is how the site is funded. The reviews are not paid for and nobody sees them before publication.
Heart Breath Mind, by Leah Lagos (2020)
The book this site's test comes from. Lagos is a clinical and sport psychologist who trains athletes and executives in HRV biofeedback, and the book turns the clinical protocol into a ten-week program for the general reader: week one finds your resonance frequency, the rest builds a twice-daily practice of about twenty minutes and adds exercises for using the breath under pressure.
Good for: a clear, practical program with a start and an end, written by someone who runs it with clients. The chapter on finding the rate is the best plain-language description we know of. Thin on: the research itself, which is summarised rather than cited in detail, and the case studies lean on elite performers. If you want the program, this is the book; if you want the evidence, read the Lehrer papers on how it works.
Breath: The New Science of a Lost Art, by James Nestor (2020)
A journalist's tour of breathing science and folklore: nasal versus mouth breathing, carbon dioxide tolerance, the 5.5-breaths-a-minute rhythm he finds in prayer traditions, and a self-experiment in which he plugs his nose for ten days. It is the book that put slow breathing in front of a general audience.
Good for: the reasons to breathe through the nose and slow down, told well. Thin on: rigour. Nestor is a reporter, some of the studies he leans on are small or old, and the book does not separate strong evidence from weak. Read it for motivation, then check the specific claims against the sources.
The Oxygen Advantage, by Patrick McKeown (2015)
McKeown teaches the Buteyko method and this book applies it to sport: nasal breathing, breathing less rather than more, a simple breath-hold self-test (the "BOLT" score) and breath-hold training. It is not about resonance frequency and does not use a pacer.
Good for: people who over-breathe, mouth-breathe in sleep, or want a training angle. Thin on: evidence for the performance claims, which mostly rest on the author's own practice and on older Buteyko studies. Useful alongside a resonance practice, not a replacement for it.
The Oxygen Advantage on Amazon
The Healing Power of the Breath, by Richard Brown and Patricia Gerbarg (2012)
Two psychiatrists who teach breathing in clinical settings and coined "coherent breathing": slow breathing at about five breaths a minute with equal inhale and exhale, which our coherent breathing page paces. Comes with an audio CD (or download) of paced tracks.
Good for: a calm, structured set of practices from clinicians, with the audio doing the pacing. Thin on: it is older, the title over-promises, and it uses a fixed rate rather than a personally tested one. If you have done the resonance test, use your own rate; if you have not, five to six breaths a minute is where most people land.
The Healing Power of the Breath on Amazon
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Breathing Frequency takes part in the Amazon Associates program. Links marked as sponsored earn a commission on purchases. We do not accept payment for reviews, have no relationship with any app or device maker, and did not receive review copies. Opinions are the publisher's own. Nothing on this page is medical advice.