VO2max: what it is, norms and how to raise it

What VO2max is

VO2max, or maximal oxygen uptake, is how much oxygen your body can use per minute at maximal effort. It is expressed per kilogram of body weight, in milliliters per kilogram per minute: ml/kg/min.

VO2max is measured precisely in an exercise test with gas analysis. You run on a treadmill or pedal a bike ergometer while the load rises gradually, and a mask analyzes the air you breathe in and out. At some point the load keeps rising but oxygen uptake plateaus: that is the maximum. This lab test is considered the gold standard.

Treadmill results are usually higher than bike results: in the FRIEND registry the treadmill medians are higher at every age. So compare your result with norms for the same type of test.

VO2max norms by age for men and women

The median VO2max for men aged 20 to 29 is 46.5 ml/kg/min and for women 36.6, and it declines by an average of 13.5%, or 4 ml/kg/min, per decade. These are data from the US FRIEND registry, updated in 2022.

The registry includes tests from 34 US labs from 1968 to 2021, and the treadmill norms are based on 16,278 of them. These are apparently healthy adults aged 20 to 89 without diagnosed cardiovascular disease or chronic obstructive pulmonary disease. VO2max was measured by gas analysis, and a test counted as maximal with a respiratory exchange ratio of at least 1.0.

A number in the table is a percentile boundary. For example, 54.5 in the "80th" column for men aged 20 to 29 means that 80% of peers have a VO2max below 54.5, and 20% above.

The authors caution that the norms come from the US and should be applied to people from other countries with care.

VO2max and 5K, 10K, half marathon and marathon times

From a race time you can work out an "effective" VO2max, called VDOT. The table shows 5K, 10K, half marathon and marathon times for VDOT from 30 to 70: for example, a one-hour 10K is a VDOT of 32.3, a 25-minute 5K is 38.3, a 4-hour marathon is 37.9.

The formulas come from coach Jack Daniels and his co-author Gilbert in the book "Oxygen Power" (1979). The first gives the oxygen cost of running at a given speed. The second gives the fraction of VO2max a person can hold for a given time: the longer the race, the smaller it is.

We computed the times from the formulas numerically and checked them against the VDOT 30 to 60 rows of the table in "Daniels' Running Formula": the calculation differs by no more than 3 seconds for 5K and 10K, 13 for the half marathon and 32 for the marathon.

VDOT is not lab VO2max. The running cost formula is the same for everyone, so an economical runner gets a VDOT above their lab VO2max, and an uneconomical one below it. And the table assumes you trained for the distance: a VDOT from a fast 5K does not promise the same marathon without long runs.

How to turn a prediction into a goal is in the guide to choosing a race goal. How fast amateurs actually run is in the articles about 5K times, 10K times and marathon times. The pace for any time is in the pace calculator.

VO2max on Garmin and Apple Watch: how accurate

Watches do not measure VO2max; they estimate it from how your heart rate relates to your speed on a run. In independent studies the average error of such estimates is about 8 to 13%: for a runner with a VO2max of 45, that is 4 to 6 points either way.

Garmin. The watch estimates VO2max during an outdoor run or brisk walk with GPS and heart rate, comparing how fast you move with how hard your heart works. Garmin advises keeping your heart rate at 70% of maximum or higher for about 15 minutes. Your profile needs the correct age and maximum heart rate.

Garmin, like Fitbit, uses an algorithm from Firstbeat, according to the authors of the INTERLIVE meta-analysis. In its white paper Firstbeat claims 95% accuracy for running, an average error of about 5%, on 2,690 runs by 79 runners whose VO2max was measured in a lab. If the maximum heart rate in the profile is 15 beats too low, the error grows to about 9%; if too high, to 7%.

Independent tests of Garmin and Fitbit watches during running showed an average error of 8 to 10.2%, more than the claimed 5%. These are data from four studies in the 2022 INTERLIVE meta-analysis (14 studies in total).

Apple Watch.In the Health app the measure is called Cardio Fitness. Apple Watch Series 3 and later estimate it during outdoor walks, runs and hikes in the Workout app, taking into account age, sex, weight, height and medications that affect heart rate. The range is 14 to 65 ml/kg/min, and the level for your age and sex is shown from age 20. The first estimate appears after a day of wearing the watch and a few workouts.

In Apple's 2021 paper the average error across 221 participants was 1.4 ± 4.7 ml/kg/min. But the comparison was with a submaximal test, not a direct maximal measurement. An independent 2025 study (30 people, maximal treadmill test) found that Apple Watch underestimated VO2max by an average of 6.07 ml/kg/min, with an average error of 13.3%.

A low cardio fitness notification, according to the same Apple paper, comes when your estimate stays in the bottom 20% of FRIEND peers (ages 20 to 59). After 60 the threshold is 18 ml/kg/min for men and 15 for women.

The INTERLIVE conclusion: workout-based estimates work for averages across large groups, but for an individual the error is large. A shift of 1 or 2 points is within the watch's own scatter: according to Apple, the median standard deviation of one person's estimates is 1.2 ml/kg/min.

How to raise VO2max

With regular endurance training, and most of all with intervals at 90 to 95% of maximum heart rate: in Helgerud's study, VO2max rose by 5.5 to 7.2% in 8 weeks.

In that study, 40 moderately trained men did one of four programs three times a week with the same total work: steady running at 70% of maximum heart rate, running at lactate threshold (85%), 15 s on, 15 s off intervals, and 4 × 4 minute intervals at 90 to 95% with 3 minutes of easy running at 70% between them. Both interval groups gained significantly more: 4 × 4 went from 55.5 to 60.4, and 15/15 from 60.5 to 64.4 ml/kg/min.

A meta-analysis of 28 studies (723 people aged 18 to 45) shows that ordinary endurance training works too: compared with no training, it added an average of 4.9 ml/kg/min to VO2max, and intervals 5.5. In a direct comparison the advantage of intervals is small, 1.2 ml/kg/min. People with a lower starting level and those who trained longer gained more.

Responses to the same training vary. In the HERITAGE study, 481 sedentary adults from 98 families followed the same 20-week bike program. VO2max rose by about 400 ml/min on average, but for some it barely changed, while others gained more than a liter per minute. The authors estimated the heritability of the response at up to 47%.

Age hardly cancels trainability. In the same HERITAGE study, participants aged 17 to 65 had similar percentage gains, although the absolute gain was smaller in older people. High, medium and low responders were found at every age, among men and women.

Intervals are hard training, and you do not need to build your whole week on them. How to combine them with easy runs and long runs is in the workout types section of the marathon training guide.

What matters more than VO2max

VO2max alone does not decide your result: lactate threshold and running economy matter just as much. VO2max sets the ceiling, and your speed depends on what fraction of it you can hold and how much oxygen you spend on each meter. That is how physiologists Michael Joyner and Edward Coyle describe endurance.

Strong runners race the marathon at about 75 to 85% of VO2max, the 10K at 90 to 100%, and the 5K close to maximum. In untrained people blood lactate starts to rise at about 60% of VO2max, in trained people at 75 to 85%. The threshold depends mainly on the oxidative capacity of the muscles, and it trains well.

Economy is how much energy running at a given speed costs. One runner can use 30 to 40% less energy per kilogram than another at the same speed. It improves slowly: in the cases described, by about 1 to 3% a year in elite athletes.

So two runners with the same VO2max can finish minutes apart. For predicting your time, a race result is more useful than VO2max from your watch.

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