Sources

The numbers and equations on this site come from the following sources. We include only content checked in the full text or abstract of original research, public guidance, or official manufacturer documentation. Each verification note explains what was checked.

1. Japan's Ministry of Health, Labour and Welfare: Physical Activity and Exercise Guide for Health Promotion 2023, INFORMATION 6, Cardiorespiratory fitness (peak oxygen uptake). (in Japanese; title translated)

   https://www.mhlw.go.jp/content/001195874.pdf

   Verification: Retrieved the full text and checked Tables 1 and 2 and the recommendations in section 6 on page 2: moderate-to-vigorous intensity, at least 30 minutes per session on at least three days per week, about 50–75% of VO₂peak, and perceived effort of “somewhat hard” (2026-10-15). Rechecked every value in both tables and section 6 when adding diagrams (2026-10-24).

2. Japan's Ministry of Health, Labour and Welfare: Physical Activity and Exercise Guide for Health Promotion 2023, INFORMATION 4, Points for safe physical activity and exercise. (in Japanese; title translated)

   https://www.mhlw.go.jp/content/001195872.pdf

   Verification: Checked pages 1–4 for health and medication checks before starting, beginning with low intensity and short duration, warm-up and cool-down, daily health checks, symptoms requiring exercise to stop, and adjustments according to next-day fatigue (2026-10-15). Retrieved the full text again on 2026-10-23 and 2026-10-24 and checked the health checklist (Figure 1: items 1–3 check restrictions; item 4 checks medication precautions; for items 5–8, proceed if already assessed and resolved), signs and symptoms (Table 1), daily condition checks (Table 3), blood pressure guidance and medication precautions.

3. Japan's Ministry of Health, Labour and Welfare: Physical Activity and Exercise Guide for Health Promotion 2023, INFORMATION 1, Strength training. (in Japanese; title translated)

   https://www.mhlw.go.jp/content/001195869.pdf

   Verification: Checked the full two-page document for effects on strength and physical function, adapting exercise to the individual, the need for rest days, and combining it with aerobic physical activity (2026-10-24). It is not used as evidence for an optimal order of strength and aerobic exercise or a percentage improvement in VO₂Max.

4. Akiyama H, Watanabe D, Miyachi M. Estimated standard values of aerobic capacity according to sex and age in a Japanese population: A scoping review. PLoS One. 2023;18(9):e0286936.

   https://doi.org/10.1371/journal.pone.0286936

   Verification: The study underlying Table 1 in MHLW 2023. Bibliographic details checked on 2026-10-15. Checked the original Strengths and limitations section on 2026-10-24: age-group comparisons are cross-sectional, may be influenced by confounding and generational differences, and do not show individual aging trajectories. The original abstract reports 21 studies and 54,614 men, whereas MHLW reports 23 studies and 54,611 men. The site's table and participant counts therefore cite the MHLW document. Rechecked the full text on 2026-10-25: data were obtained between 1977 and 2013, with limitations from participant selection, differing study methods and representativeness of the current population.

5. Han M, Qie R, Shi X, et al. Cardiorespiratory fitness and mortality from all causes, cardiovascular disease and cancer: dose-response meta-analysis of cohort studies. Br J Sports Med. 2022;56(13):733-739.

   https://doi.org/10.1136/bjsports-2021-104876

   Verification: Cited by MHLW 2023. Checked the abstract for 34 cohorts, relative risks per 1 MET (all-cause mortality 0.88, cardiovascular mortality 0.87, cancer mortality 0.93), and comparisons between the highest and lowest groups (2026-10-23).

6. Qiu S, Cai X, Sun Z, et al. Is estimated cardiorespiratory fitness an effective predictor for cardiovascular and all-cause mortality? A meta-analysis. Atherosclerosis. 2021;330:22-28.

   https://doi.org/10.1016/j.atherosclerosis.2021.06.904

   Verification: Cited by MHLW 2023. Checked the abstract for eight cohorts with more than 170,000 participants, a hazard ratio of 0.83 per 1 MET of estimated cardiorespiratory fitness, and a linear relationship (2026-10-23).

7. Kodama S, Saito K, Tanaka S, et al. Cardiorespiratory fitness as a quantitative predictor of all-cause mortality and cardiovascular events in healthy men and women: a meta-analysis. JAMA. 2009;301(19):2024-2035.

   https://doi.org/10.1001/jama.2009.681

   Verification: Checked the abstract for 33 studies, 102,980 participants in the all-cause mortality analysis, relative risks per 1 MET (all-cause mortality 0.87; coronary heart disease/cardiovascular events 0.85), and comparison of low fitness (below 7.9 METs) with high fitness (at least 10.9 METs) (2026-10-23). Checked the original Methods and Figure 3 on 2026-10-24. Values were adjusted for age and sex and standardized to a 50-year-old man before classification. The 7.9/10.9-MET cut-offs cannot be applied directly to a reader's unadjusted values.

8. Milanović Z, Sporiš G, Weston M. Effectiveness of High-Intensity Interval Training (HIT) and Continuous Endurance Training for VO2max Improvements: A Systematic Review and Meta-Analysis of Controlled Trials. Sports Med. 2015;45(10):1469-1481.

   https://doi.org/10.1007/s40279-015-0365-0

   Verification: Checked the abstract for 28 trials and 723 participants aged 18–45; endurance training +4.9 and HIT +5.5 mL/kg/min versus controls; a 1.2 mL/kg/min difference between approaches; and greater effects with lower initial fitness and longer interventions (2026-10-23).

9. Wen D, Utesch T, Wu J, et al. Effects of different protocols of high intensity interval training for VO2max improvements in adults: A meta-analysis of randomised controlled trials. J Sci Med Sport. 2019;22(8):941-947.

   https://doi.org/10.1016/j.jsams.2019.01.013

   Verification: Checked Figure 1 and Table 1 in the full text for 53 RCTs and 1,514 adults without disease. Exercise volume is the sum of high-intensity intervals, excluding recovery: high volume is at least 15 minutes and low volume at most five minutes. Interval length, volume and intervention duration were analyzed as separate classifications, with results varying by population. The study did not validate a general-public prescription combining all three conditions (2026-10-24).

10. Helgerud J, Høydal K, Wang E, et al. Aerobic high-intensity intervals improve VO2max more than moderate training. Med Sci Sports Exerc. 2007;39(4):665-671.

    https://doi.org/10.1249/mss.0b013e3180304570

    Verification: Checked the full-text Methods, Table 1 and Figure 2. The analysis included 40 male university students who exercised regularly, mean age 24.6. Training was three times per week for eight weeks. Including warm-up and cool-down, 4 × 4 took 38 minutes; 15/15 involved 47 repetitions and took about 37 minutes. Body-mass-relative values changed from 55.5 to 60.4 and 60.5 to 64.4 mL/kg/min. The 7.2% and 5.5% figures refer to absolute values in L/min; increases did not differ significantly between the interval groups (2026-10-24).

11. Tabata I. Tabata training: one of the most energetically effective high-intensity intermittent training methods. J Physiol Sci. 2019;69(4):559-572.

    https://doi.org/10.1007/s12576-019-00676-7

    Verification: Checked the author's review full text (PMC10717222) for the weekly schedule in the 1996 study: seven to eight bouts on four days per week, and 30 minutes of continuous exercise at 70% VO₂Max plus four non-exhaustive bouts on the remaining day. Exercise that copies only the timing is distinguished from the original study's intensity (2026-10-24).

12. Tabata I, Nishimura K, Kouzaki M, et al. Effects of moderate-intensity endurance and high-intensity intermittent training on anaerobic capacity and VO2max. Med Sci Sports Exerc. 1996;28(10):1327-1330.

    https://doi.org/10.1097/00005768-199610000-00018

    Verification: Checked the abstract for a six-week cycle ergometer intervention in seven participants, with VO₂Max increasing by 7 mL/kg/min, and the endurance group (70% VO₂Max, 60 minutes, five days per week) changing from 53 to 58. The high-intensity group trained five days per week, including repeated 20-second bouts at a workload with oxygen demand of about 170% of VO₂Max, with 10-second rests. The author's 2019 review confirms that four days used seven to eight bouts; the remaining day combined 30 minutes of continuous exercise with four non-exhaustive bouts (2026-10-24).

13. MacInnis MJ, Gibala MJ. Physiological adaptations to interval training and the role of exercise intensity. J Physiol. 2017;595(9):2915-2930.

    https://doi.org/10.1113/JP273196

    Verification: Checked the abstract for the distinction between HIIT (near-maximal intensity) and SIT (supramaximal intensity), and greater VO₂Max improvement with HIIT than MICT when exercise volume is matched (2026-10-23).

14. Wewege MA, Ahn D, Yu J, Liou K, Keech A. High-Intensity Interval Training for Patients With Cardiovascular Disease—Is It Safe? A Systematic Review. J Am Heart Assoc. 2018;7(21):e009305.

    https://doi.org/10.1161/JAHA.118.009305

    Verification: Checked the abstract for 23 supervised cardiac rehabilitation studies with 1,117 participants and one major cardiovascular event during HIIT (one per 17,083 sessions) (2026-10-23).

15. Nemoto K, Gen-no H, Masuki S, Okazaki K, Nose H. Effects of high-intensity interval walking training on physical fitness and blood pressure in middle-aged and older people. Mayo Clin Proc. 2007;82(7):803-811.

    https://doi.org/10.4065/82.7.803

    Verification: Checked the abstract: 246 participants, mean age 63, five months, alternating three minutes slow and three minutes brisk for at least five sets a day on at least four days a week, and walking peak oxygen uptake +9%. On 2026-10-25, checked relevant full-text pages (805–806 and 808) of the Shinshu University repository PDF through the search index: 139 analyzed overall, 42 in the interval group; no intention-to-treat analysis. Walking values were estimated from accelerometer data; cycling values used respiratory gas analysis. Full-text details specify 2–3 minutes slow at about 40%, and three minutes brisk above 70% but below 85%. Direct PDF retrieval returned 429.

16. Masuki S, Morikawa M, Nose H. High-Intensity Walking Time Is a Key Determinant to Increase Physical Fitness and Improve Health Outcomes After Interval Walking Training in Middle-Aged and Older People. Mayo Clin Proc. 2019;94(12):2415-2426.

    https://doi.org/10.1016/j.mayocp.2019.04.039

    Verification: Checked the original abstract for 679 five-month completers (mean age 65), a 14% increase in estimated peak oxygen uptake, and its relationship with training time. The plateau around 50 minutes per week is an association within the participant group, not an optimal dose established by randomized assignment to different durations. Neither slow-walking time nor total time showed a positive association with improvement (2026-10-24).

17. Garmin "Forerunner 265 Series Watch Owner's Manual — About VO2 Max. Estimates"

    https://www8.garmin.com/manuals/webhelp/GUID-F41EAFB3-6CC9-42DE-9C6C-9E358DBB0671/EN-US/GUID-3E971364-A756-4057-B22D-C41250B2A82B.html

    Verification: English manual. Checked outdoor GPS use, at least 70% of maximum heart rate for at least 10 minutes, initially inaccurate estimates that learn over several runs, the option to disable recording for trail runs, and attribution to Firstbeat and The Cooper Institute (2026-10-24).

18. Garmin "Forerunner 965 Watch Owner's Manual — Heat and Altitude Performance Acclimation"

    https://www8.garmin.com/manuals/webhelp/GUID-0221611A-992D-495E-8DED-1DD448F7A066/EN-US/GUID-70386BCC-5682-4C5C-9A87-C32AF9B6473B.html

    Verification: English manual. Checked adjustments to VO₂Max estimates and training status at temperatures above 22°C and altitudes above 800 m, and that heat acclimation requires GPS activities and smartphone weather data (2026-10-24).

19. Garmin "Forerunner 265 Series Watch Owner's Manual — Tips for Erratic Heart Rate Data"

    https://www8.garmin.com/manuals/webhelp/GUID-F41EAFB3-6CC9-42DE-9C6C-9E358DBB0671/EN-US/GUID-08BC6CE7-EB8F-4392-9B7D-714B54D19499.html

    Verification: English manual. Checked keeping the arm clean and dry, avoiding sunscreen and similar products under the device, wearing the device snugly above the wrist bone, warming up for 5–10 minutes, and warming up indoors in cold conditions (2026-10-24).

20. Polar Support. "The what and how of Running Index".

    https://support.polar.com/en/running-index

    Verification: English support page. Checked heart rate and GPS/stride sensor requirements, running-related sport profiles, at least 6 km/h for at least 12 minutes, the importance of maximum and resting heart rate settings, and allowance for uphill running when altitude data are available (2026-10-24).

21. Polar Research Center. "Polar Running Index". White paper (4 April 2021).

    https://www.polar.com/img/static/whitepapers/pdf/polar-running-index-white-paper.pdf

    Verification: Checked the PDF full text: without an altitude sensor, uphill running yields lower values and downhill running higher values; short interruptions are excluded; validation with an uncalibrated indoor foot pod gave lower values (50 ± 8 versus 55 ± 7, n = 47). The validation used an older algorithm version (2026-10-24).

22. Firstbeat Technologies. "Automated Fitness Level (VO2max) Estimation with Heart Rate and Speed Data". White paper (30 June 2017 edition).

    https://www.firstbeat.com/wp-content/uploads/2017/06/white_paper_VO2max_30.6.2017.pdf

    Verification: Checked the PDF full text for use of reliable segments only, excluding soft surfaces, steep downhill sections and traffic-light stops, as well as segments affected by prolonged heart-rate drift. Checked about 5% running estimation error (79 people, 2,690 runs) and errors of about 9% or 7% when maximum heart rate was set 15 beats too low or too high, respectively. This is a company document without peer review (2026-10-24).

23. Howard J, Ellis R, Fortner CK, Doyle JA, Otis J. Validity of the Garmin Forerunner 265 to predict VO2max and race performance times. J Med Eng Technol. 2026;1-12.

    https://doi.org/10.1080/03091902.2026.2741912

    Verification: Checked the abstract: after 12 weeks of training, the smartwatch estimate of 45.00 exceeded the measured value of 42.43, and percentage error was below 10% (2026-10-24).

24. Gielen J, Van Oost CN, Debard G, et al. Accuracy of Optical Heart Rate Measurements for 10 Commercial Wearables in Different Climate Conditions and Activities. JMIR Form Res. 2026;10:e85186.

    https://doi.org/10.2196/85186

    Verification: Checked the original full text for 45 participants and 10 devices: no significant difference in heart-rate accuracy between 10°C, 23°C and 36°C in short indoor tests. Increased error during intermittent walking occurred in some devices. These findings are not generalized to prolonged outdoor exercise or all smartwatches (2026-10-24).

25. Fleg JL, Morrell CH, Bos AG, et al. Accelerated longitudinal decline of aerobic capacity in healthy older adults. Circulation. 2005;112(5):674-682.

    https://doi.org/10.1161/CIRCULATIONAHA.105.545459

    Verification: Checked the abstract for a longitudinal study of 810 people aged 21–87, with median follow-up of 7.9 years. Decline accelerated from 3–6% per decade in the twenties and thirties to over 20% per decade from the seventies onward, with similar patterns across physical activity quartiles (2026-10-23).

26. Sawka MN, Young AJ, Cadarette BS, Levine L, Pandolf KB. Influence of heat stress and acclimation on maximal aerobic power. Eur J Appl Physiol Occup Physiol. 1985;53(4):294-298.

    https://doi.org/10.1007/BF00422841

    Verification: Checked the abstract for 13 men: VO₂Max was 8% lower at 49°C than at 21°C, or 7% lower after acclimation (2026-10-24).

27. Cheuvront SN, Kenefick RW, Montain SJ, Sawka MN. Mechanisms of aerobic performance impairment with heat stress and dehydration. J Appl Physiol. 2010;109(6):1989-1995.

    https://doi.org/10.1152/japplphysiol.00367.2010

    Verification: Checked the abstract: heat lowers VO₂Max and increases relative exercise intensity; dehydration exceeding 2% of body mass consistently impairs aerobic performance (2026-10-24).

28. Goulet ED. Effect of exercise-induced dehydration on endurance performance: evaluating the impact of exercise protocols on outcomes using a meta-analytic procedure. Br J Sports Med. 2013;47(11):679-686.

    https://doi.org/10.1136/bjsports-2012-090958

    Verification: Checked the original abstract for endurance performance in 15 papers and 122 participants, with dehydration effects differing by exercise protocol. Findings of small performance effects with dehydration of 4% or less in time trials, and the author's view on drinking to thirst, do not establish safety limits for dehydration or heat illness. Public-facing hydration advice uses MHLW safety guidance (2026-10-24).

29. Hamilton MT, Gonzalez-Alonso J, Montain SJ, Coyle EF. Fluid replacement and glucose infusion during exercise prevent cardiovascular drift. J Appl Physiol. 1991;71(3):871-877.

    https://doi.org/10.1152/jappl.1991.71.3.871

    Verification: Rechecked the abstract: ten endurance-trained participants cycled for two hours at 22°C. Between minutes 20 and 120 without fluid replacement, stroke volume fell 15% and heart rate rose 10%; with fluid replacement, stroke volume was maintained and heart rate rose 5% (2026-10-25).

30. Wingo JE, Lafrenz AJ, Ganio MS, Edwards GL, Cureton KJ. Cardiovascular drift is related to reduced maximal oxygen uptake during heat stress. Med Sci Sports Exerc. 2005;37(2):248-255.

    https://doi.org/10.1249/01.MSS.0000152731.33450.95

    Verification: Checked the abstract: at 35°C and 60% VO₂Max, heart rate rose 12% from minute 15 to minute 45 (151 to 169), associated with reduced VO₂Max. Reconfirmed that the abstract reports a 19% reduction in VO₂Max (4.4 to 3.6 L/min) (2026-10-24).

31. Coyle EF, González-Alonso J. Cardiovascular drift during prolonged exercise: new perspectives. Exerc Sport Sci Rev. 2001;29(2):88-92.

    https://doi.org/10.1097/00003677-200104000-00009

    Verification: Checked the abstract for cardiovascular drift, with stroke volume declining from 10–20 minutes after exercise begins (2026-10-24).

32. Craven J, McCartney D, Desbrow B, et al. Effects of Acute Sleep Loss on Physical Performance: A Systematic and Meta-Analytical Review. Sports Med. 2022;52(11):2669-2690.

    https://doi.org/10.1007/s40279-022-01706-y

    Verification: Checked full-text Methods and Results: acute sleep loss in healthy adults (no more than six hours in 24 hours, compared with normal sleep above six hours), 69 papers and 227 outcomes, with mean performance −7.56%. Multiple nights of sleep loss were excluded. Reductions were consistent after total deprivation or early waking, with smaller effects on morning tasks. This does not establish the same percentage change in VO₂Max (2026-10-25).

33. Durstenfeld MS, Sun K, Tahir P, et al. Use of Cardiopulmonary Exercise Testing to Evaluate Long COVID-19 Symptoms in Adults: A Systematic Review and Meta-analysis. JAMA Netw Open. 2022;5(10):e2236057.

    https://doi.org/10.1001/jamanetworkopen.2022.36057

    Verification: Checked the abstract for nine studies (464 people with symptoms and 359 without): people with symptoms at least three months after infection had peak oxygen uptake lower by a mean 4.9 mL/kg/min, with low certainty of evidence (2026-10-23).

34. Ried-Larsen M, Aarts HM, Joyner MJ. Effects of strict prolonged bed rest on cardiorespiratory fitness: systematic review and meta-analysis. J Appl Physiol. 2017;123(4):790-799.

    https://doi.org/10.1152/japplphysiol.00415.2017

    Verification: Checked the abstract for 80 studies and 949 participants, predominantly young and over 90% male: VO₂Max declined linearly during 1–90 days of bed rest, at 0.43% per day for body-mass-relative values (2026-10-23).

35. Wehrlin JP, Hallén J. Linear decrease in VO2max and performance with increasing altitude in endurance athletes. Eur J Appl Physiol. 2006;96(4):404-412.

    https://doi.org/10.1007/s00421-005-0081-9

    Verification: Checked the abstract for eight endurance athletes: VO₂Max declined from 66 to 55 mL/kg/min between 300 and 2,800 m altitude, a 6.3% decline per 1,000 m, with a decline already present at 800 m (2026-10-23).

36. Gullestad L, Hallen J, Medbø JI, et al. The effect of acute vs chronic treatment with beta-adrenoceptor blockade on exercise performance, haemodynamic and metabolic parameters in healthy men and women. Br J Clin Pharmacol. 1996;41(1):57-67.

    https://doi.org/10.1111/j.1365-2125.1996.tb00159.x

    Verification: Checked the original abstract for 15 healthy men and women: after two weeks of propranolol versus placebo, peak heart rate changed from 186 to 134 and peak oxygen uptake from 42.3 to 39.1 mL/kg/min. Effects vary with the medication and treatment duration; these are not uniform changes for all beta-blockers (2026-10-24).

37. Chatterjee S, Dey SK, Nag SK. Maximum oxygen uptake capacity of smokers of different age groups. Jpn J Physiol. 1987;37(5):837-850.

    https://doi.org/10.2170/jjphysiol.37.837

    Verification: Checked the original Methods and Results for 176 sedentary Indian men aged 20–59 (84 smokers and 92 nonsmokers). Smokers had significantly lower values only in the 20–29 age group (38.9 versus 42.1 mL/kg/min). Significant negative correlations with smoking amount and duration were also findings within smokers in that age group (2026-10-24).

38. Spicuzza L, Pennisi F, Caci G, et al. Improved aerobic capacity in a randomized controlled trial of noncombustible nicotine and tobacco products. Sci Rep. 2025;15(1):19104.

    https://doi.org/10.1038/s41598-025-03904-w

    Verification: Checked the abstract and full text: this was a secondary analysis of a trial switching to e-cigarettes or heated tobacco products, using estimates from the Chester Step Test (2026-10-24). It is not used to quantify changes in directly measured VO₂Max from smoking cessation in general; numerical findings were removed from the article.

39. Engel FA, Masur L, Sperlich B, Düking P. Validity of VO2max estimates from the Forerunner 245 smartwatch in highly vs. moderately trained endurance athletes. Eur J Appl Physiol. 2026;126(1):591-603.

    https://doi.org/10.1007/s00421-025-05923-x

    Verification: Checked the original full text for 35 endurance athletes, with mean differences of −4.73 mL/kg/min at the first measurement and −4.05 at the second. The approximately 4.7 lower value refers to the first measurement. Underestimation was greater in the higher-fitness group; these values are not correction factors for general users (2026-10-24).

40. Carrier B, Marten Chaves S, Navalta JW. Validation of Aerobic Capacity (VO2max) and Pulse Oximetry in Wearable Technology. Sensors. 2025;25(1):275.

    https://doi.org/10.3390/s25010275

    Verification: Checked the original abstract, Methods and Results: 19 participants, Garmin fēnix 6 MAPE 7.05% and concordance correlation coefficient 0.73 against measured 30-second averages, with a Garmin HRM-Run chest strap (2026-10-25; full-text sections also checked through PMC search extraction). The Table 1 caption alone says n=20, conflicting with n=19 in the abstract, Methods and Results. Reasons for exclusions are not inferred.

41. Lambe R, Schumann M, Donnelly L, et al. Accuracy of VO2 max Estimates From Apple Watch Series 10. Mayo Clin Proc Digit Health. 2026;4(2):100357.

    https://doi.org/10.1016/j.mcpdig.2026.100357

    Verification: Checked the abstract for 40 healthy adults: Apple Watch Series 10 estimates averaged 6.25 below measured values, with limits of agreement −18.23 to 5.73, percentage error 13.2%, and correct percentile-band classification in 14% (2026-10-23). Retrieved the abstract again on 2026-10-24 and confirmed that bands used FRIEND reference standards, with a further 34% in an adjacent band. Checked the original full text (PMC13141568) on 2026-10-24: 40 enrolled, 35 analyzed, mean age 22.7; five in the same band and 12 in an adjacent band. Participants were predominantly young, healthy and highly fit; this was not a validation in people receiving low fitness notifications.

42. Karstoft K, Thorsen IK, Nielsen JS, et al. Health benefits of interval walking training. Appl Physiol Nutr Metab. 2024;49(7):1002-1007.

    https://doi.org/10.1139/apnm-2023-0595

    Verification: Checked the abstract: adherence is high in short-term studies, but long-term adherence remains a challenge (2026-10-23).

43. Uth N, Sørensen H, Overgaard K, Pedersen PK. Estimation of VO2max from the ratio between HRmax and HRrest – the Heart Rate Ratio Method. Eur J Appl Physiol. 2004;91(1):111-115.

    https://doi.org/10.1007/s00421-003-0988-y

    Verification: Rechecked the original abstract: coefficient 15.3; standard errors of estimate 2.7 and 4.7 mL/kg/min; 46 well-trained men aged 21–51, with 10 used to derive the factor and 36 for validation. Other populations require direct validation, and these errors are not individual upper limits. Also checked the appendix published in the 2005 erratum (2026-10-25).

44. Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol. 2001;37(1):153-156.

    https://doi.org/10.1016/S0735-1097(00)01054-8

    Verification: Checked the original PubMed abstract: maximum heart rate = 208 − 0.7 × age in healthy adults, a meta-analysis of 351 studies with 18,712 participants and validation in 514 participants. This is a population regression equation, not an individual measurement (2026-10-25).

45. Apple Support: Track your cardio fitness levels (published 16 September 2026). (in Japanese; title translated)

    https://support.apple.com/ja-jp/108790

    Verification: Checked the Japanese and English (en-us/108790) full texts for supported models, eligible workouts, initial-estimate requirements, viewing in the Health app, the estimation range, minimum age of 20, and the overestimation caution (2026-10-23). Retrieved again on 2026-10-24 and confirmed notifications for fitness low relative to age and sex, further notifications if it remains low, and updates to past estimates.

46. Google Health Help: About VO₂Max. (in Japanese; title translated)

    https://support.google.com/googlehealth/answer/14237924?hl=ja

    Verification: Rechecked the Japanese version (which notes possible AI translation) and English full text for measurement requirements, initial estimates, calculation methods, app navigation and six fitness levels (2026-10-25). The current text recommends reviewing trends over three months or more and running faster if able; this corrects the previous note that the pace advice was absent. Our article explains outdoor GPS running requirements and navigation without encouraging readers to push to a high intensity merely to obtain an estimate.

47. Samsung Japan: Galaxy Watch9 40mm product page, fitness index information. (in Japanese; title translated)

    https://www.samsung.com/jp/watches/galaxy-watch/galaxy-watch9-40mm-cream-bluetooth-sm-l340nzejxjp/

    Verification: Checked measurement guidance: at least 10 minutes of brisk outdoor walking (at least 4 km/h) or running, and when results are reflected (2026-10-23).

48. Samsung US Support "Work out with your Wear OS Galaxy Watch"

    https://www.samsung.com/us/support/answer/ANS10003401/

    Verification: US support page, in English. Checked One UI 4.1 or later, at least 4 km/h on a flat route for 10 minutes, GPS, continuous heart-rate monitoring, starting a run from the smartwatch, and results near the bottom of the summary (2026-10-23).

49. Garmin: INSTINCT 2 SERIES Owner’s Manual, VO2 Max. (in Japanese; title translated)

    https://www8.garmin.com/manuals-apac/webhelp/instinct2series/JA-JP/GUID-D5794FF1-8341-4B82-8BCE-99E6A7C0C6E0-2536.html

    Verification: One example of a specific model. Checked the heart-rate monitor requirement, outdoor running for at least 10 minutes with GPS, cycling requirements, profile and maximum-heart-rate settings, possible inaccuracy of initial estimates and data providers (2026-10-23).

50. Android Developers "Health Connect data types"

    https://developer.android.com/health-and-fitness/guides/health-connect/plan/data-types

    Verification: Checked the VO₂Max data type (Vo2MaxRecord) and its read/write permissions (2026-10-23).

51. Molina-Garcia P, et al. Validity of Estimating the Maximal Oxygen Consumption by Consumer Wearables: A Systematic Review with Meta-analysis and Expert Statement of the INTERLIVE Network. Sports Med. 2022;52:1577-1597.

    https://doi.org/10.1007/s40279-021-01639-y

    Verification: Checked the full text (PMC9213394) for 14 studies and 403 participants; exercise-based estimates had a mean difference of −0.09 and limits of agreement ±9.83, while resting estimates had a mean difference of 2.17 and limits of agreement ±15.24 (mL/kg/min). Also checked the conclusions (2026-10-23).

52. Lambe R, O'Grady B, Baldwin M, Doherty C. Investigating the accuracy of Apple Watch VO2 max measurements: A validation study. PLoS One. 2025;e0323741.

    https://doi.org/10.1371/journal.pone.0323741

    Verification: Checked the abstract and full text for 30 enrolled and 28 analyzed participants, wearing the device for 5–10 days, comparison with a maximal treadmill exercise test, a mean underestimation of 6.07 mL/kg/min, mean absolute error 6.92 and mean absolute percentage error 13.31% (2026-10-23). Retrieved the abstract again on 2026-10-24 and confirmed 95% limits of agreement of −6.11 to 18.26 (measured minus smartwatch; these are not observed minimum and maximum values). Rechecked the original Results and population on 2026-10-24: 30 enrolled, 28 analyzed, predominantly young and highly fit. The mean difference is not extrapolated to individual corrections or the misclassification rate of low fitness notifications.

53. Apple. "Using Apple Watch to Estimate Cardio Fitness with VO2 max" (May 2021).

    https://www.apple.com/healthcare/docs/site/Using_Apple_Watch_to_Estimate_Cardio_Fitness_with_VO2_max.pdf

    Verification: Checked the 13-page English full text for low cardio fitness notifications: age 20 or older, user-enabled in the Health app, issued for consistently low estimates; for ages 20–59, the lowest fifth of the sex- and decade-specific FRIEND distribution; for age 60 or older, 18 mL/kg/min for men and 15 for women. Also checked estimation requirements (gradient below 5%, GPS, elevated heart rate), causes of inaccuracy, validation in 221 people (difference from estimates based on submaximal testing: 1.4 ± 4.7 mL/kg/min), and error when heart-rate-lowering medication was entered (11.8 ± 4.0 to 1.6 ± 3.1) (2026-10-24). The current support page does not state whether today's thresholds are the same.

54. Kaminsky LA, Arena R, Myers J. Reference Standards for Cardiorespiratory Fitness Measured With Cardiopulmonary Exercise Testing: Data From the Fitness Registry and the Importance of Exercise National Database. Mayo Clin Proc. 2015;90(11):1515-1523.

    https://doi.org/10.1016/j.mayocp.2015.07.026

    Verification: Checked the abstract for eight US centers, January 2014–February 2015, 7,783 maximal treadmill tests in men and women aged 20–79 without cardiovascular disease, decade-specific percentiles, and median values declining from 48.0 for men and 37.6 for women in their twenties to 24.4 and 18.3 mL/kg/min in their seventies, approximately 10% per decade (2026-10-24). Checked the full text on 2026-10-24: January 2014–February 2015 was the data submission period. The approximately 10% figure is a cross-sectional comparison between age groups, not change in the same people followed over time.

55. Paterson DH, Cunningham DA, Koval JJ, St Croix CM. Aerobic fitness in a population of independently living men and women aged 55-86 years. Med Sci Sports Exerc. 1999;31(12):1813-1820.

    https://doi.org/10.1097/00005768-199912000-00018

    Verification: Checked the abstract for treadmill testing in 298 independently living men and women aged 55–86, as part of a random survey, and estimated minimum levels compatible with independent living at age 85 of approximately 18 mL/kg/min for men and 15 for women (2026-10-24).

56. Garmin Support: Frequently asked questions about the Garmin Connect app. (in Japanese; title translated)

    https://support.garmin.com/ja-JP/?faq=N7qM9eVuzl77PNYKV8ORX5

    Verification: Checked the official Japanese text under “How can I view my data?”: VO₂Max is available under Performance Stats, accessed from More at the bottom right (2026-10-24).

No specialist review; sources provided|Content last checked: October 15, 2026|Editorial policy