This page explains what the resonance frequency test on this site does, the research it rests on, what it can and cannot tell you, and who should talk to a clinician before trying slow breathing. Every claim has a numbered source at the bottom.
What resonance frequency breathing is
Your heart rate rises a little on each inhale and falls on each exhale. When you breathe slowly, at around five to six breaths a minute, those swings line up with a slower rhythm in blood pressure that the body's baroreflex produces, and the swings in heart rate get much larger [1, 4]. The breathing rate at which the swings are largest is your resonance frequency. It is personal: in one data set of 56 adults it ranged across the 4.5 to 6.5 range, was lower in taller people and lower in men than in women, and had no relationship to age or weight [2].
The size of those swings is one way to describe heart rate variability (HRV), the beat-to-beat variation in heart rate [5]. Breathing at your resonance frequency is the core exercise of HRV biofeedback, a training method developed by Paul Lehrer, Evgeny Vaschillo and colleagues at Rutgers [1, 3].
How the test works
The protocol is the one in Lehrer and Vaschillo's 2000 training manual [3] and, for the general reader, in Leah Lagos's Heart Breath Mind [6]: breathe at 6.5, 6, 5.5, 5 and 4.5 breaths a minute, about two minutes each, and find the rate that produces the largest heart-rate swings. On this site you follow a circle that grows as you inhale and shrinks as you exhale, with the exhale longer than the inhale (a 40:60 split, as the manual prescribes [3]). Between rates you rest for a minute and rate how the last rate felt. Seven-rate and three-minute versions are available for people whose resonance sits higher, or who want a longer sample.
The timing at each rate: 6.5 a minute is 3.7 seconds in and 5.5 out; 6 is 4 and 6; 5.5 is 4.4 and 6.5; 5 is 4.8 and 7.2; 4.5 is 5.3 and 8. Normal resting breathing for adults is 12 to 20 a minute [4], so every rate in the test is far slower than you breathe without thinking about it.
What the test measures, and what it does not
Without a sensor, the test measures how each rate felt to you. That is a reasonable starting point: the rates that produce large heart-rate swings are usually also the ones that feel easiest and most settling, and Lagos suggests exactly this felt-sense method for readers without a device [6]. It is not a measurement. Two rates can feel the same; the result can change with mood, caffeine or a cold. So the site tells you to repeat the test on another day and trust a rate that wins twice.
With a Bluetooth chest strap and an HRV app, you can enter the app's HRV reading for each rate, and the highest reading decides instead of your rating. How to do that. Wrist and finger wearables measure HRV overnight and are not built for a two-minute paced test.
What the research supports
- A 2020 meta-analysis of 58 randomized controlled studies of HRV biofeedback found a small to moderate effect in its favour, largest for anxiety, depression, anger and athletic or artistic performance and smallest for PTSD, sleep and quality of life, with each estimate resting on a small number of studies. The authors describe it as useful as a complementary approach and call for more research on specific uses [7].
- A 2017 study compared 15 minutes of breathing at the personal resonance frequency with breathing one breath a minute faster and with sitting quietly. The resonance group reported higher positive mood, showed a higher LF/HF HRV ratio than the control group, and had lower systolic blood pressure during a stressful mental task afterwards [8].
- A 2018 systematic review of 15 studies in healthy people found slow breathing (under 10 breaths a minute) associated with higher HRV, changes in brain activity, and reports of comfort, relaxation, alertness and reduced anxiety and arousal. The studies were small [9].
- A 2023 randomized study over one month found that five minutes a day of breathwork, and cyclic sighing in particular, improved mood and lowered breathing rate more than an equal period of mindfulness meditation [10]. That study is the basis of the physiological sigh page.
These are associations from small or moderate studies, and results differ from person to person. Nothing here is proof that slow breathing will do anything in particular for you.
Who should check with a clinician first
Anyone who is pregnant, has a heart or lung condition, a history of fainting, panic disorder or epilepsy, or is being treated for a mental health condition. Slow breathing can lower blood pressure and heart rate, so people on medication for either should ask their clinician. Stop if you feel dizzy or short of breath: that usually means the breath is too deep or too slow for you today. Nothing on this site is medical advice, a diagnosis or a treatment.
Privacy and code
The pacer runs in your browser. Your ratings and any HRV figures stay on your device (the result is kept in your browser's local storage so you can see it next time); nothing is sent to us. The timing code is at /source/breath.js, with automated tests that check the rate tables, the test plan and the result logic. Found a mistake or a better source? Tell us.
Sources
- Lehrer PM, Gevirtz R. Heart rate variability biofeedback: how and why does it work? Frontiers in Psychology. 2014;5:756. PubMed 25101026
- Vaschillo EG, Vaschillo B, Lehrer PM. Characteristics of resonance in heart rate variability stimulated by biofeedback. Applied Psychophysiology and Biofeedback. 2006;31(2):129-142. PubMed 16838124
- Lehrer PM, Vaschillo E, Vaschillo B. Resonant frequency biofeedback training to increase cardiac variability: rationale and manual for training. Applied Psychophysiology and Biofeedback. 2000;25(3):177-191. PubMed 10999236
- Russo MA, Santarelli DM, O'Rourke D. The physiological effects of slow breathing in the healthy human. Breathe. 2017;13(4):298-309. PubMed 29209423
- Shaffer F, Ginsberg JP. An overview of heart rate variability metrics and norms. Frontiers in Public Health. 2017;5:258. PubMed 29034226
- Lagos L. Heart Breath Mind: Train Your Heart to Conquer Stress and Achieve Success. Houghton Mifflin Harcourt; 2020. Reviewed on our books page.
- Lehrer P, Kaur K, Sharma A, et al. Heart rate variability biofeedback improves emotional and physical health and performance: a systematic review and meta analysis. Applied Psychophysiology and Biofeedback. 2020;45(3):109-129. PubMed 32385728
- Steffen PR, Austin T, DeBarros A, Brown T. The impact of resonance frequency breathing on measures of heart rate variability, blood pressure, and mood. Frontiers in Public Health. 2017;5:222. PubMed 28890890
- Zaccaro A, Piarulli A, Laurino M, et al. How breath-control can change your life: a systematic review on psycho-physiological correlates of slow breathing. Frontiers in Human Neuroscience. 2018;12:353. PubMed 30245619
- Balban MY, Neri E, Kogon MM, et al. Brief structured respiration practices enhance mood and reduce physiological arousal. Cell Reports Medicine. 2023;4(1):100895. PubMed 36630953