VO₂max: What It Is and Why Aerobic Capacity Matters for More Than Just Athletes

VO₂max has long been a feature of sports watches and fitness apps, yet it is still often seen as a number for runners and cyclists. What exactly does it measure, and why do researchers consider it one of the most important indicators of health?

What VO₂max Is and What It Measures

VO₂max (maximal oxygen consumption) is the highest rate at which the body can take in and use oxygen during maximal exertion. It is the main measure of cardiorespiratory fitness (American Heart Association, Importance of Assessing Cardiorespiratory Fitness in Clinical Practice, 2016).

VO₂max reflects the work of several links at once: the lungs, which oxygenate the blood; the heart and blood vessels, which deliver it to the muscles; and the muscle cells, which use oxygen to produce energy. The measure is expressed in milliliters of oxygen per kilogram of body weight per minute (mL/kg/min) to account for differences in body weight between people.

VO₂max is most accurately determined with a cardiopulmonary exercise test: a person performs exercise of increasing intensity on a treadmill or cycle ergometer while a special device analyzes the air the person exhales (Kaminsky et al., Mayo Clin Proc, 2022). It can also be estimated using smartwatches and fitness trackers, which assess the measure indirectly, using algorithms that mostly rely on heart rate data (Molina-Garcia et al., Sports Med, 2022).

What VO₂max Says About Health

VO₂max is the main indicator of cardiorespiratory fitness, which is linked not only to athletic performance: it is one of the strongest and most consistent predictors of morbidity and mortality among adults (Lang et al., Br J Sports Med, 2024).

A review of 26 meta-analyses that together covered more than 20.9 million observations from 199 cohort studies showed that people with a high level of cardiorespiratory fitness had a 53% lower risk of all-cause death than people with a low level (HR 0.47; 95% CI 0.39–0.56) (Lang et al., Br J Sports Med, 2024).

The link between fitness and mortality risk is not limited to comparing the highest level with the lowest: it can be seen even with small differences between people. Studies often express fitness in METs (metabolic equivalent of task): the multiple of energy expenditure relative to rest, which equals 1 MET. Converted to VO₂max, 1 MET is approximately 3.5 mL/kg/min. Each 1 MET higher level of fitness was associated with an 11–17% lower risk of death from any cause (Lang et al., Br J Sports Med, 2024).

The findings on the link between VO₂max and health come from observational studies, so they describe associations rather than causal relationships. This does not reduce the measure’s prognostic value: it can help predict an outcome without being its cause. The link between fitness level and mortality, as well as a number of chronic diseases, including cardiovascular ones, is also replicated in meta-analyses of cohort studies (Lang et al., Br J Sports Med, 2024).

The American Heart Association (AHA) recommends an annual assessment of cardiorespiratory fitness in adults as part of a routine checkup, at least with estimation algorithms that do not require an exercise test. Such an assessment improves the accuracy of cardiovascular disease prediction because cardiorespiratory fitness carries information independent of classic risk factors (American Heart Association, Importance of Assessing Cardiorespiratory Fitness in Clinical Practice, 2016).

For more on what else cardiovascular risk depends on, see the article The Cause of Cardiovascular Disease Isn’t Only “Bad” Cholesterol.

How Much VO₂max Depends on Genetics

Cardiorespiratory fitness is influenced by age, sex, genetics, lifestyle, and training regimen (American Heart Association, Importance of Assessing Cardiorespiratory Fitness in Clinical Practice, 2016). The role of genetics is assessed through heritability: this measure shows how much differences between people in a given trait are related to differences in their genes. According to a meta-analysis of twin and family studies, the heritability of cardiorespiratory fitness ranges from 44% to 68%, depending on the study and the measurement method (Joensuu et al., Scand J Med Sci Sports, 2026). These estimates apply to populations: they do not determine what a particular person’s VO₂max will be and do not set a ceiling above which it cannot rise.

The genetic component of cardiorespiratory fitness is polygenic: many DNA variants are associated with it, and each one on its own explains only a small share of the differences between people (Joensuu et al., Scand J Med Sci Sports, 2026). That is why genetic predisposition is assessed cumulatively, using a polygenic score that sums the contribution of hundreds of thousands of variants and shows a person’s position relative to a reference population.

Why the Same Training Gives Different Results

Genetics is associated with both the baseline VO₂max and how much it increases in response to training.

The HERITAGE study analyzed data from more than 700 adults aged 17 to 65 who had previously led a sedentary lifestyle and for 20 weeks followed the same, fully controlled aerobic training program. On average, VO₂max increased by 384 mL of oxygen per minute, but the standard deviation was 202 mL/min, meaning the spread between participants was very large (Sarzynski et al., Med Sci Sports Exerc, 2022).

The gain in VO₂max proved more similar among members of the same family than among people from different families, and the heritability of the gain was estimated at 47% (Sarzynski et al., Med Sci Sports Exerc, 2022).

Participants with low, medium, and high gains appeared in all age groups, among men and women, and at any baseline fitness level (Sarzynski et al., Med Sci Sports Exerc, 2022). So a small gain on one program describes an individual’s response to that program and does not mean that aerobic exercise is useless.

For more on why people recover differently after exertion, see the article Recovery Speed After Training: The Role of Genetics.

What Genetic Data Add to the Number on Your Watch

Genetic predisposition to fitness is also linked to disease risk. In the Finnish FinnGen cohort (more than 260,000 people), a higher polygenic fitness score was associated with a lower risk of several diseases: for each standard deviation of the score, the risk of type 2 diabetes was 4% lower (HR 0.96) and the risk of all-cause death was 2% lower (HR 0.98). For type 2 diabetes, the association was also confirmed in the Norwegian HUNT cohort (Joensuu et al., Scand J Med Sci Sports, 2026).

In HUNT, people with a high measured VO₂max had a lower resting heart rate, systolic blood pressure, and body mass index and better cholesterol levels than people with a low one (Joensuu et al., Scand J Med Sci Sports, 2026).

The “Sports Potential and Physical Performance” genetic test from Apixmed Prism analyzes genetic features associated with cardiorespiratory fitness, heart rate recovery after exercise, resting heart rate, and heart rate variability. The results should be compared with an exercise test and training dynamics and discussed with a coach or sports physician.

Frequently Asked Questions About VO₂max

How Accurately Do Smartwatches and Fitness Trackers Estimate VO₂max?

Such measurements should be treated as a rough guide. A meta-analysis of 14 studies showed that VO₂max estimates calculated by devices during running barely differ on average from the laboratory result, but for an individual the discrepancy can reach 10 mL/kg/min (Molina-Garcia et al., Sports Med, 2022). The exact value comes only from a laboratory test, in which the air a person exhales is analyzed.

What VO₂max Level Is Normal for My Age?

There is no single value for everyone: the measure depends on age and sex. According to the FRIEND reference standards, compiled from treadmill laboratory tests of healthy adults, the average in men aged 40–49 is about 36 mL/kg/min, and in women about 27; at ages 60–69 it is about 25 and 20 mL/kg/min, respectively (Kaminsky et al., Mayo Clin Proc, 2022). Overall, the measure declines by roughly 4 mL/kg/min with each decade. According to the AHA, a level below 5 METs (about 17.5 mL/kg/min) is associated with a high risk of death, and a level above 8–10 METs (roughly 28–35 mL/kg/min) with higher survival (American Heart Association, Importance of Assessing Cardiorespiratory Fitness in Clinical Practice, 2016).

Can You Increase VO₂max After Age 40?

According to the AHA, in previously sedentary adults who start doing regular aerobic exercise, VO₂max rises by about 10%. In addition, a meta-analysis of 41 studies of healthy older adults (mean participant age of 60 or older) found that aerobic training raised VO₂max by an average of 3.8 mL/kg/min (16%) compared with a control group (American Heart Association, Importance of Assessing Cardiorespiratory Fitness in Clinical Practice, 2016). The gain varies between people, though: in the HERITAGE study, more than 700 adults followed the same 20-week program, and in some the gain was large while in others it was small (Sarzynski et al., Med Sci Sports Exerc, 2022). A small gain describes a particular person’s response to a particular program, not the futility of training.

Explore your genetic traits with Apixmed Prism.

Genetic test results are not a diagnosis or a substitute for a doctor’s consultation. The Apixmed Prism report provides genetic context that complements the results of examinations and helps you make decisions together with your doctor.

Sources

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2. Kaminsky, L. A., Arena, R., Myers, J., Peterman, J. E., Bonikowske, A. R., Harber, M. P., Medina Inojosa, J. R., Lavie, C. J., & Squires, R. W. (2022). Updated reference standards for cardiorespiratory fitness measured with cardiopulmonary exercise testing: Data from the Fitness Registry and the Importance of Exercise National Database (FRIEND). Mayo Clinic Proceedings, 97(2), 285–293. https://doi.org/10.1016/j.mayocp.2021.08.020

3. Molina-Garcia, P., Notbohm, H. L., Schumann, M., Argent, R., Hetherington-Rauth, M., Stang, J., et al. (2022). Validity of estimating the maximal oxygen consumption by consumer wearables: A systematic review with meta-analysis and expert statement of the INTERLIVE network. Sports Medicine, 52(7), 1577–1597. https://doi.org/10.1007/s40279-021-01639-y

4. Lang, J. J., Prince, S. A., Merucci, K., Cadenas-Sanchez, C., Chaput, J.-P., Fraser, B. J., Manyanga, T., McGrath, R., Ortega, F. B., Singh, B., & Tomkinson, G. R. (2024). Cardiorespiratory fitness is a strong and consistent predictor of morbidity and mortality among adults: An overview of meta-analyses representing over 20.9 million observations from 199 unique cohort studies. British Journal of Sports Medicine, 58(10), 556–566. https://doi.org/10.1136/bjsports-2023-107849

5. Joensuu, L., Lukander, V., Herranen, P., Tynkkynen, N. P., Kujala, U., Lopéz-Bueno, R., Nordeidet, A. N., Klevjer, M., Øvretveit, K., Wisløff, U., Bye, A., Ekelund, U., Ollikainen, M., FinnGen, & Sillanpää, E. (2026). Evaluation of genetics in the association between cardiorespiratory fitness and health: Insights from a genome-wide polygenic score for cardiorespiratory fitness in the FinnGen and HUNT cohorts. Scandinavian Journal of Medicine & Science in Sports, 36(5), e70291. https://doi.org/10.1111/sms.70291

6. Sarzynski, M. A., Rice, T. K., Després, J.-P., Pérusse, L., Tremblay, A., Stanforth, P. R., Tchernof, A., Barber, J. L., Falciani, F., Clish, C., Robbins, J. M., Ghosh, S., Gerszten, R. E., Leon, A. S., Skinner, J. S., Rao, D. C., & Bouchard, C. (2022). The HERITAGE Family Study: A review of the effects of exercise training on cardiometabolic health, with insights into molecular transducers. Medicine & Science in Sports & Exercise, 54(5S), S1–S43. https://doi.org/10.1249/MSS.0000000000002859