hrv.expert

HRV standards and key references

Every page on hrv.expert lists its own sources. These are the standards and reviews the whole site relies on for how HRV is defined, measured and read.

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Where a page defines a measure such as RMSSD, SDNN or HF power, it follows the 1996 Task Force standards below. Where newer work has changed how a measure is read, as with the LF/HF ratio, the page says so and cites that work. See our editorial policy for how sources are chosen and checked.

The age and sex reference values that our HRV checker uses are listed row by row, with a CSV download, in our HRV reference values dataset.

Measurement standards and guidelines

These define the HRV measures, how to record them and how to report them.

  1. Set the definitions still used for the main HRV measures (SDNN, RMSSD, pNN50, LF, HF and LF/HF), the frequency bands, the 5-minute short-term recording and the need to clean beat data before analysis. It was published at the same time in the European Heart Journal (1996;17:354–381).

    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

  2. A committee report for the Society for Psychophysiological Research on where HRV comes from, how to quantify it and the pitfalls in reading it.

    Berntson GG, Bigger JT Jr, Eckberg DL, et al.. Heart rate variability: origins, methods, and interpretive caveats. Psychophysiology 1997;34(6):623–648. doi:10.1111/j.1469-8986.1997.tb02140.x

  3. A European position statement that reviews the newer, non-linear HRV methods developed since 1996 and finds their clinical use still limited.

    Sassi R, Cerutti S, Lombardi F, et al.. Advances in heart rate variability signal analysis: joint position statement by the e-Cardiology ESC Working Group and the European Heart Rhythm Association co-endorsed by the Asia Pacific Heart Rhythm Society. Europace 2015;17(9):1341–1353. doi:10.1093/europace/euv015

  4. Practical recommendations for planning HRV studies, analysing the data and reporting it, with a focus on vagally mediated measures such as RMSSD and HF power.

    Laborde S, Mosley E, Thayer JF. Heart rate variability and cardiac vagal tone in psychophysiological research: recommendations for experiment planning, data analysis, and data reporting. Frontiers in Psychology 2017;8:213. doi:10.3389/fpsyg.2017.00213

  5. A checklist of standard steps for collecting and analysing HRV, written for cardiology and cardiac rehabilitation.

    Catai AM, Pastre CM, Godoy MF, et al.. Heart rate variability: are you using it properly? Standardisation checklist of procedures. Brazilian Journal of Physical Therapy 2020;24(2):91–102. doi:10.1016/j.bjpt.2019.02.006

  6. The Society for Psychophysiological Research’s updated committee report on measuring heart rate and HRV with ECG and optical (PPG) sensors, with checklists for reporting.

    Quigley KS, Gianaros PJ, Norman GJ, et al.. Publication guidelines for human heart rate and heart rate variability studies in psychophysiology, Part 1: physiological underpinnings and foundations of measurement. Psychophysiology 2024;61(9):e14604. doi:10.1111/psyp.14604

  7. An updated guideline on recording and analysing heart rate and HRV at rest and at work, including quality control, for occupational medicine.

    Sammito S, Thielmann B, Klussmann A, et al.. Guideline for the application of heart rate and heart rate variability in occupational medicine and occupational health science. Journal of Occupational Medicine and Toxicology 2024;19:15. doi:10.1186/s12995-024-00414-9

What the measures reflect

Reviews that explain each metric and correct common misreadings.

  1. An overview of the time-domain, frequency-domain and non-linear HRV measures, what each is thought to reflect, and published norms.

    Shaffer F, Ginsberg JP. An overview of heart rate variability metrics and norms. Frontiers in Public Health 2017;5:258. doi:10.3389/fpubh.2017.00258

  2. Reviews the heart’s anatomy and nervous control, including why vagal signals change the heart rate within a second and sympathetic ones take several seconds.

    Shaffer F, McCraty R, Zerr CL. A healthy heart is not a metronome: an integrative review of the heart’s anatomy and heart rate variability. Frontiers in Psychology 2014;5:1040. doi:10.3389/fpsyg.2014.01040

  3. Showed that the usual Poincaré plot measures, including SD1 and SD2, capture the same linear features as existing HRV measures.

    Brennan M, Palaniswami M, Kamen P. Do existing measures of Poincaré plot geometry reflect nonlinear features of heart rate variability?. IEEE Transactions on Biomedical Engineering 2001;48(11):1342–1347. doi:10.1109/10.959330

  4. Showed that SD1 and RMSSD are the same measure apart from a fixed scale factor, so they should not be reported as separate findings.

    Ciccone AB, Siedlik JA, Wecht JM, et al.. Reminder: RMSSD and SD1 are identical heart rate variability metrics. Muscle & Nerve 2017;56(4):674–678. doi:10.1002/mus.25573

  5. Argued that the LF/HF ratio cannot measure the balance between the sympathetic and parasympathetic systems.

    Billman GE. The LF/HF ratio does not accurately measure cardiac sympatho-vagal balance. Frontiers in Physiology 2013;4:26. doi:10.3389/fphys.2013.00026

  6. Concluded that LF power reflects baroreflex function, which steadies blood pressure, rather than sympathetic tone.

    Goldstein DS, Bentho O, Park MY, Sharabi Y. Low-frequency power of heart rate variability is not a measure of cardiac sympathetic tone but may be a measure of modulation of cardiac autonomic outflows by baroreflexes. Experimental Physiology 2011;96(12):1255–1261. doi:10.1113/expphysiol.2010.056259

Normal values

Reference data for short recordings in healthy adults.

  1. Pooled short-term HRV values from 44 studies with 21,438 healthy adults and found them lower than the values in the 1996 standards.

    Nunan D, Sandercock GRH, Brodie DA. A quantitative systematic review of normal values for short-term heart rate variability in healthy adults. Pacing and Clinical Electrophysiology 2010;33(11):1407–1417. doi:10.1111/j.1540-8159.2010.02841.x

  2. Reported 5-minute HRV values by age and sex in 1,906 healthy adults aged 25 to 74 from a German population study.

    Voss A, Schroeder R, Heitmann A, et al.. Short-term heart rate variability: influence of gender and age in healthy subjects. PLOS ONE 2015;10(3):e0118308. doi:10.1371/journal.pone.0118308

  3. A meta-analysis of 172 studies on how HRV differs between healthy women and men.

    Koenig J, Thayer JF. Sex differences in healthy human heart rate variability: a meta-analysis. Neuroscience and Biobehavioral Reviews 2016;64:288–310. doi:10.1016/j.neubiorev.2016.03.007

Data quality and devices

How bad beats and sensor type change the numbers.

  1. Explains how ectopic beats and recording errors distort HRV, and compares the ways of editing beat data.

    Peltola MA. Role of editing of R–R intervals in the analysis of heart rate variability. Frontiers in Physiology 2012;3:148. doi:10.3389/fphys.2012.00148

  2. An automatic method to find and correct missed, extra and misplaced beats in beat-to-beat data.

    Lipponen JA, Tarvainen MP. A robust algorithm for heart rate variability time series artefact correction using novel beat classification. Journal of Medical Engineering & Technology 2019;43(3):173–181. doi:10.1080/03091902.2019.1640306

  3. Reviewed studies comparing pulse rate variability from optical (PPG) sensors with ECG-based HRV, and when one can stand in for the other.

    Schäfer A, Vagedes J. How accurate is pulse rate variability as an estimate of heart rate variability? A review on studies comparing photoplethysmographic technology with an electrocardiogram. International Journal of Cardiology 2013;166(1):15–29. doi:10.1016/j.ijcard.2012.03.119

Health, training and breathing

Landmark and review papers behind the applied pages.

  1. Among 808 people who survived a heart attack, those with a 24-hour SDNN below 50 ms had 5.3 times the risk of death during follow-up of those above 100 ms.

    Kleiger RE, Miller JP, Bigger JT Jr, Moss AJ. Decreased heart rate variability and its association with increased mortality after acute myocardial infarction. American Journal of Cardiology 1987;59(4):256–262. doi:10.1016/0002-9149(87)90795-8

  2. Explains how averaged lnRMSSD can be used to follow training in elite endurance athletes.

    Plews DJ, Laursen PB, Stanley J, et al.. Training adaptation and heart rate variability in elite endurance athletes: opening the door to effective monitoring. Sports Medicine 2013;43(9):773–781. doi:10.1007/s40279-013-0071-8

  3. Reviews heart rate and HRV measures for monitoring training, and why averages over several days work better than single readings.

    Buchheit M. Monitoring training status with HR measures: do all roads lead to Rome?. Frontiers in Physiology 2014;5:73. doi:10.3389/fphys.2014.00073

  4. Reviews how HRV biofeedback at about 6 breaths a minute works, with the baroreflex as the best-supported explanation.

    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