Sources and methods
Every number on whatsmypulse comes from a published source. This page lists all of them, grouped by topic, with the date each was last checked.
How we pick and check sources
Primary sources come first: the journal article that introduced an equation, the government report that published a survey table, or the guideline page of the organisation that issued it. Where organisations disagree, each version is shown and labelled rather than blended into one number. Survey tables are copied digit by digit from the original documents and compared against them before publishing. Equipment-maker conventions, such as the five heart-rate zones, are cited as such and not presented as medical guidance.
The camera reader’s analysis code was written for this site. It is tested automatically against synthetic pulse signals with known rates, noise, frame-timing jitter and harmonic distortion: any rate it shows must be within 3 beats per minute of the true value, and signals that are too noisy must produce no number. It has not been tested in a clinical study.
Spotted an error or an outdated figure? Write to hello@whatsmypulse.com.
Maximum heart rate
- Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol 2001;37(1):153–156. doi:10.1016/S0735-1097(00)01054-8. Checked 2026-10-09.
- Fox SM, Naughton JP, Haskell WL. Physical activity and the prevention of coronary heart disease. Ann Clin Res 1971;3(6):404–432 (as reproduced and analysed by Robergs & Landwehr 2002). PubMed 4945367. Checked 2026-10-09.
- Robergs RA, Landwehr R. The surprising history of the “HRmax = 220 − age” equation. J Exerc Physiol Online 2002;5(2):1–10. asep.org. Checked 2026-10-09.
- Gellish RL, Goslin BR, Olson RE, et al. Longitudinal modeling of the relationship between age and maximal heart rate. Med Sci Sports Exerc 2007;39(5):822–829. doi:10.1097/mss.0b013e31803349c6. Checked 2026-10-09.
- Gulati M, Shaw LJ, Thisted RA, et al. Heart rate response to exercise stress testing in asymptomatic women: the St. James Women Take Heart Project. Circulation 2010;122(2):130–137. doi:10.1161/CIRCULATIONAHA.110.939249. Checked 2026-10-09.
- Nes BM, Janszky I, Wisløff U, Støylen A, Karlsen T. Age-predicted maximal heart rate in healthy subjects: the HUNT fitness study. Scand J Med Sci Sports 2013;23(6):697–704. doi:10.1111/j.1600-0838.2012.01445.x. Checked 2026-10-09.
Zones and intensity
- Karvonen MJ, Kentala E, Mustala O. The effects of training on heart rate; a longitudinal study. Ann Med Exp Biol Fenn 1957;35(3):307–315. PubMed 13470504. Checked 2026-10-09.
- Bishop DJ, et al. Physical activity and exercise intensity terminology: a joint ACSM Expert Statement and ESSA Consensus Statement. Med Sci Sports Exerc 2025;57(11):2599–2613 — Table 1, column “ACSM (2020)”, i.e. ACSM’s Guidelines for Exercise Testing and Prescription, 11th ed. doi:10.1249/mss.0000000000003795. Checked 2026-10-09.
- American Heart Association. Target Heart Rates Chart (last reviewed Aug 12, 2024). heart.org. Checked 2026-10-09.
- American Heart Association. American Heart Association Recommendations for Physical Activity in Adults and Kids (last reviewed Jan 19, 2024). heart.org. Checked 2026-10-09.
- U.S. Department of Health and Human Services. Physical Activity Guidelines for Americans, 2nd edition, 2018 (pp. 20, 56, 60, 109). odphp.health.gov. Checked 2026-10-09.
- Centers for Disease Control and Prevention. How to Measure Physical Activity Intensity (updated Dec 4, 2025). cdc.gov. Checked 2026-10-09.
- Polar. Heart rate zones: the basics (training guide). polar.com. Checked 2026-10-09.
- Garmin. How you can train by heart rate zones using Garmin (blog, Mar 28, 2025). garmin.com. Checked 2026-10-09.
- Storoschuk KL, Moran-MacDonald A, Gibala MJ, Gurd BJ. Much ado about Zone 2: a narrative review assessing the efficacy of Zone 2 training for improving mitochondrial capacity and cardiorespiratory fitness in the general population. Sports Med 2025;55(7):1611–1624. doi:10.1007/s40279-025-02261-y. Checked 2026-10-09.
Resting heart rate
- Ostchega Y, Porter KS, Hughes J, Dillon CF, Nwankwo T. Resting pulse rate reference data for children, adolescents, and adults: United States, 1999–2008. National Health Statistics Reports no. 41. National Center for Health Statistics, 2011 (Tables 1–3). cdc.gov. Checked 2026-10-09.
- Fleming S, Thompson M, Stevens R, et al. Normal ranges of heart rate and respiratory rate in children from birth to 18 years of age: a systematic review of observational studies. Lancet 2011;377(9770):1011–1018 (Web Table 5). PMC3789232. Checked 2026-10-09.
- Quer G, Gouda P, Galarnyk M, Topol EJ, Steinhubl SR. Inter- and intraindividual variability in daily resting heart rate and its associations with age, sex, sleep, BMI, and time of year: retrospective, longitudinal cohort study of 92,457 adults. PLoS One 2020;15(2):e0227709. doi:10.1371/journal.pone.0227709. Checked 2026-10-09.
Taking a pulse and when to get help
- American Heart Association. All About Heart Rate (Pulse) (last reviewed May 13, 2024). heart.org. Checked 2026-10-09.
- MedlinePlus (U.S. National Library of Medicine). Pulse (review date Jan 1, 2025). medlineplus.gov. Checked 2026-10-09.
Camera measurement
- Coppetti T, Brauchlin A, Müggler S, et al. Accuracy of smartphone apps for heart rate measurement. Eur J Prev Cardiol 2017;24(12):1287–1293. doi:10.1177/2047487317702044. Checked 2026-10-09.
- De Ridder B, Van Rompaey B, Kampen JK, Haine S, Dilles T. Smartphone apps using photoplethysmography for heart rate monitoring: meta-analysis. JMIR Cardio 2018;2(1):e4. doi:10.2196/cardio.8802. Checked 2026-10-09.