hrv.expert

Chest-strap HRV test

Connect a chest strap, sit still for two minutes, and get your RMSSD and other HRV numbers worked out from the time between your heartbeats. Or let it pace your breathing to find your resonance breathing rate.

What you will do

What you'll need: a chest strap that sends RR intervals, such as the Polar H10, and Chrome or Edge on a computer or Android phone with Bluetooth on.

  1. Wet and wear the strap

    Wet both electrode pads, then fasten the strap snugly just below your chest muscles.

  2. Connect in Chrome or Edge

    Press Connect your strap and pick it from the browser's list. iPhone browsers cannot connect.

  3. Sit still for 2 minutes

    Sit or lie down, breathe normally and do not talk. The test first waits 15 seconds for your heart rate to settle.

  4. Read your result

    You get RMSSD, SDNN and heart rate, and can download the intervals or open them in the HRV calculator.

What do you want to do?
Recording length

Your browser shows a list of nearby straps. Pick yours. The test then waits 15 s for the reading to settle before it starts recording.

Nothing you record leaves this device unless you are signed in and choose to save the result; then only its RMSSD, mean heart rate and time are sent. Privacy

Straps and browsers that work

  • A chest strap that sends beat-to-beat (RR) intervals over Bluetooth, such as the Polar H10 or H9, Garmin HRM-Pro or Wahoo TICKR. Most watches and arm bands send heart rate only, which is not enough.
  • Chrome or Edge on a computer (Windows, Mac, ChromeOS or Linux) or on an Android phone, with Bluetooth switched on.
  • Safari, and every browser on iPhone and iPad, cannot connect to a strap. On an iPhone, try the Camera HRV test instead, or enter a number from your app in the HRV checker.

How to take a good reading

  1. Measure at the same time each day, ideally soon after waking, before coffee and exercise.
  2. Wet the strap's electrodes and wear it snug, just below the chest muscles.
  3. Sit or lie down and rest. The test waits 15 seconds for your heart rate to settle before it records.
  4. Breathe normally, keep still and do not talk until the recording ends.
  5. Close other apps that connect to the strap. Many straps talk to only one app or device at a time.

The test removes beats that look like missed or extra beats before working out your numbers. If too many are removed, it shows no result rather than a wrong one.

Read more

Find your resonance breathing rate

For most adults there is one slow breathing rate, somewhere between 4.5 and 6.5 breaths a minute, at which heart rate rises and falls most with each breath. At that rate the swing caused by breathing lines up with the swing from the baroreflex, the reflex that steadies blood pressure, so the two add up (Lehrer and Gevirtz, 2014; Shaffer and Meehan, 2020). HRV biofeedback trains people to breathe at their own rate.

Slow breathing raises vagally mediated HRV while you do it. A meta-analysis of 223 studies found it higher right after a session and after several weeks of practice too (Laborde and colleagues, 2022). The wider health claims are less settled: Lehrer and Gevirtz note that few uses of HRV biofeedback have strong support from controlled studies.

How to use it

  1. Choose "Find your resonance breathing rate" above, then connect your strap.
  2. Sit upright and follow the circle: breathe in as it grows and out as it shrinks. With reduced motion switched on, follow the words and the count instead.
  3. The pacer runs at 6.5, 6, 5.5, 5 and 4.5 breaths a minute, 2 minutes each, about 10 minutes in all. Breathe gently through your nose and do not force big breaths.

Stop and breathe normally if you feel dizzy, light-headed or short of breath. Breathing slowly and deeply can wash out carbon dioxide; shallower, smoother breaths help. Shaffer and Meehan advise against the test if a pacemaker sets your heart rhythm. This is a breathing exercise, not a treatment, and it cannot diagnose anything.

What the numbers mean

For each rate the finder takes the highest minus the lowest heart rate within each breath, then averages over the breaths at that rate. That is the peak-to-trough heart rate swing, one of the signs Shaffer and Meehan list and the simplest to measure without a breathing sensor. The rate with the largest swing is recommended. LF power (variability between 0.04 and 0.15 Hz, the Task Force band) and RMSSD are shown beside it for context.

This is a shorter version of a clinic assessment. Clinicians weigh several signs together, rest between rates and check breathing with a sensor. The finder goes straight from one rate to the next and leaves out the first breath at each new rate while you settle in. If two rates come within 10% of each other, either will do.

Sources

  • Lehrer PM, Gevirtz R. Heart rate variability biofeedback: how and why does it work? Frontiers in Psychology 2014;5:756. doi:10.3389/fpsyg.2014.00756
  • Shaffer F, Meehan ZM. A practical guide to resonance frequency assessment for heart rate variability biofeedback. Frontiers in Neuroscience 2020;14:570400. doi:10.3389/fnins.2020.570400
  • 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. doi:10.1023/A:1009554825745
  • Laborde S, Allen MS, Borges U, et al. Effects of voluntary slow breathing on heart rate and heart rate variability: a systematic review and a meta-analysis. Neuroscience and Biobehavioral Reviews 2022;138:104711. doi:10.1016/j.neubiorev.2022.104711
  • Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. Heart rate variability: standards of measurement, physiological interpretation and clinical use. Circulation 1996;93(5):1043–1065. doi:10.1161/01.CIR.93.5.1043