VO2 Max: What It Is and How to Improve It (Science-Backed)

A VO2 max chart shows how your aerobic fitness compares with people of your age and sex. On the main US reference built from lab-measured tests (the FRIEND registry), a good VO2 max is anything at or above the 50th percentile: about 38 mL/kg/min for a man in his 40s and about 27 for a woman in her 40s. Above the 75th percentile (45 and 32 at that age) is high fitness. Below the 25th percentile is low, and that is the group with the highest death rates in long-term studies. The full chart is below, plus how to measure your number and raise it.

What is your VO2 max? Get an estimate in two minutes, plus your fitness age, with our free VO2 max calculator. No treadmill needed.

Planning your easy sessions? Our free Zone 2 heart rate calculator gives you all five heart rate zones for your age.

What is VO2 max, and what does the number mean?

VO2 max is the most oxygen your body can take in, carry and use per minute during all-out exercise. It reflects your heart, lungs, blood and muscles working as one system, which is why researchers treat it as the main measure of cardiorespiratory fitness.

It is written in millilitres of oxygen per kilogram of body weight per minute (mL/kg/min), so people of different sizes can be compared. Two related terms:

• VO2 peak. The highest value reached on a test. Lab reports and the newest reference charts often use peak values; for everyday purposes, treat it as your VO2 max.
• METs. Many health studies report fitness in metabolic equivalents. In one large meta-analysis, a 1-MET difference in fitness corresponded to being able to run about 1 km/h (0.6 mph) faster (4).

VO2 max chart by age and sex

These numbers come from FRIEND (the Fitness Registry and the Importance of Exercise National Database), which uses tests where oxygen uptake was actually measured with a mask, not estimated from treadmill time. The 2015 FRIEND standards pooled 7,783 maximal treadmill tests from adults aged 20 to 79 without known heart disease, collected by 8 US labs in 2014 and 2015 (1). Each number is VO2 max in mL/kg/min, copied from the study’s percentile table.

Men: VO2 max by age (treadmill, mL/kg/min)

Women: VO2 max by age (treadmill, mL/kg/min)

How to read it: below the first number, you are in the bottom quarter for your age and sex. Between the first and second, below average. Between the second and third, above average. Above the third, you are in the top quarter.

Three things the chart does not tell you:

• It is a treadmill chart. FRIEND’s 2022 update, built on 22,379 tests from 34 labs, found median values were higher on a treadmill than on a bike (2). If your lab test was on a bike, expect a lower number for the same fitness.
• The newer standards run a little lower. The same update put the treadmill standards 1.5 to 4.6 mL/kg/min below the 2015 figures above (2), so treat this chart as slightly on the demanding side.
• Average is not the same as optimal. The FRIEND authors note that some people in the data set had diabetes, obesity or other risk factors, and that Norwegian lab norms run clearly higher than American ones (1). The US middle is a reference point, not a health target.

What is a good VO2 max for your age?

There is no single cut-off, but the percentile groups from the biggest outcome study make a sensible scale. In a Cleveland Clinic study of 122,007 adults who did a treadmill test (fitness estimated from speed and incline), people were ranked against others of their age and sex as low (below the 25th percentile), below average (25th to 49th), above average (50th to 74th), high (75th to 97.6th) or elite (97.7th and up) (3). Applied to the FRIEND chart:

• Good: at or above the middle column for your age.
• Very good: at or above the right-hand column.
• Excellent: top 10% for your age, shown in the table below.
• Worth acting on: below the left-hand column. For comparison, Apple Watch’s optional low cardio fitness alert flags ages 20 to 59 when estimates stay in the lowest fifth of FRIEND for age and sex. From 60 it uses 18 mL/kg/min for men and 15 for women, levels Apple links to the ability to live independently in very old age (6).

Top 10%: 90th percentile VO2 max (treadmill, mL/kg/min)

Two quick examples. A 52-year-old man at 40 mL/kg/min sits just above the 75th percentile (39.7), so his fitness is high for his age. A 45-year-old woman at 25 sits between the 25th (22.1) and 50th (26.7) percentiles: below average, but within reach of average with a few months of training.

Why VO2 max matters more after 40

VO2 max falls with age. Across FRIEND’s age groups, the median dropped from 48.0 in men in their 20s to 24.4 in their 70s, and from 37.6 to 18.3 in women: roughly 10% per decade (1). The 2022 update put the treadmill decline at 13.5% per decade (2). Following the same people over time tells a starker story. In the Baltimore Longitudinal Study of Aging, 810 adults lost 3–6% per decade in their 20s and 30s, but more than 20% per decade in their 70s, and the decline sped up whatever their activity level (5). Training does not stop the slide; it sets the height you slide from.

That height matters. In the Cleveland Clinic study, followed for a median 8.4 years, the elite group had an 80% lower risk of death than the low group after adjustment (hazard ratio 0.20). Being below average rather than above average carried a hazard ratio of 1.41, the same as smoking (1.41) and similar to diabetes (1.40). The authors saw no upper limit to the benefit, and the elite group still did better than the high group in people aged 70 and over (3).

A 33-study meta-analysis of healthy adults points the same way: each 1-MET higher level of fitness was linked to 13% lower all-cause mortality and 15% fewer heart and cardiovascular events (4). These are observational data, and the Cleveland Clinic authors are explicit that their study cannot prove fitness causes longer life, and unmeasured factors may play a part (3). But fitness is one of the few strong predictors you can change.

There is a simpler cardiovascular number you can check every morning: see our related breakdown on what a healthy resting heart rate looks like. VO2 max and HRV often appear side by side on the same watch. For the other number, see what counts as a good heart rate variability and how training changes it.

How to estimate your VO2 max

The three options differ a lot in precision.

A lab cardiopulmonary exercise test, offered by some sports medicine and cardiology clinics, is the only one that gives you a number you can place on the chart with confidence. The 12-minute run, known as the Cooper test, is the best-validated of the time-based field tests: across 123 studies its results correlated at 0.78 with lab-measured VO2 max (7). That is useful for tracking yourself, but too loose to pin you to an exact percentile.

How accurate is your watch’s VO2 max?

No wrist device measures VO2 max directly; each one estimates it, usually from how your heart rate responds to your pace on a run or walk. Apple’s method paper is a good example. The watch needs an outdoor walk, run or hike on fairly flat ground, with GPS and a decent rise in heart rate, and it predicts your max from that submaximal effort (6). Anything that pushes your heart rate up for the same pace can drag the estimate down: extreme heat, dehydration, caffeine, a recent move to altitude, a heavy backpack or soft sand. Heart-rate-lowering medicines such as beta blockers need to be entered in the Health app or the estimate will be off (6).

How close does it get? A meta-analysis of 14 validation studies found that watches using exercise data were almost spot-on for groups (average bias −0.09 mL/kg/min) but individual readings could still miss by up to about 10 points either way. Devices relying on resting data did worse, overestimating by 2.17 on average with even wider errors (8). The review was partly funded by the tech company Huawei. In a 2026 test of the Apple Watch Series 10 against lab measurements in 40 adults, the watch read 6.25 mL/kg/min low on average, and placed only 14% of people in their correct FRIEND percentile band (9).

So use the watch number as a trend line, not a verdict. Compare readings taken in similar conditions, and trust a change that holds over several weeks more than any single score. Which devices estimate credibly, and which need a chest strap, is covered in our guide to the best watches and trackers for VO2 max.

How to improve VO2 max

VO2 max responds well to training at any age. The recipe is plenty of aerobic volume, a small dose of hard intervals, and patience.

1. Get your weekly volume up to the guideline. The World Health Organization recommends 150–300 minutes of moderate activity a week, or 75–150 minutes of vigorous activity, or a mix, with extra benefit beyond 300 minutes (10). Most of it can be easy, conversational work: see our Zone 2 cardio guide, and use the Zone 2 calculator to set your easy-day heart rate. Our breakdown of how much exercise you actually need per week covers the dose in more detail.
2. Add one or two interval sessions a week. In a classic trial of 40 moderately trained men, one group did 4 × 4 minutes at 90–95% of maximum heart rate with 3 minutes of easy jogging between, three times a week for 8 weeks. Its VO2 max rose 7.2%, clearly more than in groups doing the same total work at a steady 70% or 85% of maximum heart rate (11). A meta-analysis of 28 studies (723 adults aged 18 to 45) found both kinds of training raise VO2 max a lot (about 4.9 mL/kg/min for steady endurance work, 5.5 for intervals, against no exercise), with intervals adding a small extra 1.2 (12). For the trade-offs, see HIIT vs steady-state cardio. If running intervals are not for you, Japanese interval walking is a gentler way in.
3. Think in months, not weeks. In that same meta-analysis, longer programs produced bigger gains for both kinds of training (12).
4. Keep lifting. Strength work is not a VO2 max tool, but the WHO guideline also asks for muscle-strengthening activity on 2 or more days a week (10). Our guide to exercises to stay strong after 40 covers the basics.
5. Treat supplements as a rounding error. Beetroot juice is the best-studied one here. A 2026 meta-analysis of 38 trials in 703 healthy adults found a small overall improvement in VO2 max (standardised effect 0.24, or 0.19 after adjusting for publication bias). It was larger in recreationally active people (0.38) and not clearly present in highly trained athletes (0.07) (13). See can you eat beets every day.

A realistic week for a busy adult: three 40-minute brisk walks, easy rides or jogs, one interval session, and two short strength workouts. For an extreme example of human endurance, our look at what the Tarahumara teach us about running covers ultra distances in thin sandals and Harvard footstrike research.

Can you raise your VO2 max after 50 or 60?

Yes. A meta-analysis of 41 controlled trials in 2,102 sedentary older adults (average age 60 or more) found endurance training raised VO2 max by 3.78 mL/kg/min on average, a 16.3% improvement over control groups. Gains were larger in programs lasting more than 20 weeks, at a moderate 60–70% of VO2 max (14). That is roughly a 1-MET gain, the size of improvement FRIEND’s authors note has been linked to 10–25% lower mortality in earlier studies (1).

On the chart, that gain could move a 65-year-old woman from 18 mL/kg/min (just above the 25th percentile of 17.2) to about 22: above the median (20.0) and closing on the 75th percentile (23.8). Because the decline speeds up after 60 (5), holding your number steady is itself a win.

Before you add hard intervals: if you have a heart condition, diabetes or kidney disease, take heart-rate-lowering medicine, or have been inactive for a long time, check with your doctor first, and build up with steady walking. Stop and get medical help if you feel chest pain or pressure, unusual breathlessness, dizziness or a racing, irregular heartbeat during exercise. A low VO2 max on a watch is a reason to talk to your doctor, not a diagnosis.

This article is for general information and is not medical advice. See our medical disclaimer. More free tools are on our tools page.

Sources

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9. Lambe R, et al. Accuracy of VO2 max estimates from Apple Watch Series 10. Mayo Clin Proc Digit Health. 2026;4(2):100357. PubMed 42094313
10. Bull FC, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med. 2020;54(24):1451-1462. PubMed 33239350
11. Helgerud J, et al. Aerobic high-intensity intervals improve VO2max more than moderate training. Med Sci Sports Exerc. 2007;39(4):665-671. PubMed 17414804
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