The test on the home page works by feel. With a heart rate chest strap and an HRV app it becomes a measurement: you breathe at each rate while the app records, write down the app's HRV figure for that rate, and the highest figure wins. This page says what you need and what to write down.
What you need
- A Bluetooth chest strap that reports beat-to-beat (RR) intervals, not just heart rate. The Polar H10 is the one most HRV apps recommend; older straps and most wrist or finger wearables send only an averaged heart rate, which is not enough.
- An HRV app that shows a live or per-session figure. Elite HRV, HRV4Biofeedback (built for exactly this protocol) and Kubios HRV all do. We have no relationship with any of them and earn nothing from the mention.
- About fifteen minutes, sitting, with the strap wetted and snug just below the chest muscles.
Which number to write down
The research protocol picks the rate with the largest swings in heart rate, the difference between the peak on each inhale and the trough on each exhale [Lehrer, Vaschillo & Vaschillo 2000]. Apps report this in one of two ways:
- Heart-rate amplitude or peak-to-trough (HRV4Biofeedback and Kubios show this directly, in beats per minute). Best match to the protocol. Write it down as is.
- RMSSD (Elite HRV and most general apps), a standard time-domain HRV metric [Shaffer & Ginsberg 2017]. It rises with resonance breathing too and works for comparing rates within one session. Write down the figure the app shows for that two-minute window, not a whole-day or overnight value.
Use the same metric for every rate. The test's result box only uses the HRV column when every rate has a figure; if one is missing, it falls back to your comfort ratings.
Running the test with a strap
- Put the strap on, open the app, confirm it sees the strap and shows live RR intervals.
- Start the test here. At each rate, start a fresh recording in the app when the circle starts, and stop it when the rate ends (two minutes).
- In the rest screen, rate how it felt and type the app's figure for that recording into the HRV box.
- At the end, the result names the rate with the highest figure. If two rates are within a few percent of each other, treat it as a tie and re-test those two on another day, at three minutes each.
Reading the result
A clear winner at, say, 5.5 breaths a minute means practising at 5.5 (inhale 4.4 seconds, exhale 6.5) on the pacer. One careful measurement, confirmed on a second day, is enough to choose a practice rate. Re-test if the practice starts to feel wrong, after a long break, or if your app's figures at the chosen rate fall over several sessions. Full references are on how it works.
Nothing on this site is medical advice. If you are pregnant, have a heart or lung condition, a history of fainting, panic disorder or epilepsy, or are treated for a mental health condition or for blood pressure, ask your clinician before starting slow-breathing practice.