What Is VO2max, and Can You Actually Raise It?

Short answer: VO2max is the most oxygen your body can take in and use per minute when you're working flat out, and yes, you can raise it. How much depends mostly on where you start: people coming from little training often gain 10% or more within two to three months, while people who already train regularly usually gain much less. The right kind of hard intervals raise it most, and individual responses vary widely. VO2max also isn't the whole story of how fast you are, and the number on your watch is only a rough estimate.

What VO2max actually measures

Your muscles burn fuel with oxygen to make energy. As you speed up, they need more oxygen, and your heart, lungs and blood work harder to deliver it. VO2max is the point where that system tops out: you go faster, but your oxygen use stops rising.

It's usually written in millilitres of oxygen per kilogram of body weight per minute (ml/kg/min), so a lighter and a heavier athlete can be compared. Sometimes it's given in litres per minute instead: the raw total, without dividing by body weight. Both appear below.

Think of VO2max as the size of your aerobic engine. It sets the upper limit for endurance performance, because no one can work above 100% of their VO2max for long (1). A bigger engine gives you more room, but how fast you go in a race depends on how you use it.

What limits it: mostly your heart

For healthy people exercising with large muscle groups, as in running or cycling, the evidence points mainly to delivery. The main limit is usually how much oxygen-rich blood your heart can pump to the working muscles; how much oxygen the muscles extract from that blood plays a smaller part (1, 2). When oxygen delivery changes, for example at altitude, VO2max changes with it. And when training raises VO2max, it's mostly because the heart can pump more blood per minute at maximum (1).

Athletes don't get their high VO2max from a faster heartbeat: their maximum heart rate is, if anything, lower than non-athletes' (2). Elite endurance athletes have a high VO2max mainly because their hearts are large and flexible. They relax quickly and fill with a big volume of blood before each beat, then pump it out (2).

Your muscles still matter, just not for the ceiling itself. Training adds mitochondria (the parts of muscle cells that use oxygen to make energy) and improves how muscles use fat. That helps you go faster at efforts below your maximum, which is where you spend almost all of a race (1).

Why VO2max isn't the whole story

If VO2max decided races, the highest number would always win. It doesn't. Research on champions points to three factors working together: VO2max, the lactate threshold, and efficiency (3).

The lactate threshold is the effort above which lactate starts to build up in your blood and fatigue comes on sooner. It decides what fraction of your VO2max you can actually hold in a race. Together, VO2max and threshold set the amount of oxygen you can keep using over time, which Joyner and Coyle call your "performance VO2" (3).

Efficiency, or economy, is how much oxygen it costs you to run at a given pace or ride at a given power. Two runners with the same VO2max can run very different times if one of them needs less oxygen per kilometre (3).

In Bassett and Howley's review, the speed at your lactate threshold came out as the best single physiological predictor of distance running performance, because it combines all three (1). In engine terms: VO2max is the engine's size, threshold is how hard you can run it for long periods, and economy is how far you go on each litre of fuel.

How VO2max is measured, and how far to trust your watch

The reference method is a graded exercise test in a lab. You run on a treadmill or ride a stationary lab bike while wearing a mask that measures the oxygen you breathe in and the carbon dioxide you breathe out. The effort increases in steps until you can't continue. Even then, researchers debate exactly when someone has reached their true maximum (4).

Your watch doesn't measure oxygen at all. It estimates VO2max from your heart rate, your pace or power, and personal details such as age and sex. A meta-analysis, which pools the results of many studies, combined 14 validation studies and found two very different kinds of estimate (5):

• Estimates based on resting information (heart rate at rest, age, body size) overestimated VO2max on average, and for an individual the error could be very large.
• Estimates based on exercise data (heart rate against pace or power during real workouts) were close to the lab value on average, but the error for an individual was still sizeable.

The authors concluded that exercise-based estimates work well for describing groups of people, but still need improvement before they're accurate enough for individuals in sport or clinical settings (5).

So treat the number with caution. The validation studies compared single readings with lab tests; they didn't test whether watches track your changes over time, and the authors advise caution about using them that way (5). As a rule of thumb, a jump or drop of a few points in a week is more likely noise than a real change. If you follow the number at all, look only for large shifts that hold for months in similar conditions, and check them against the benchmark in step 6. We'd trust your pace or power at threshold more.

Can you raise it? Yes, and here's by how much

A meta-analysis of 28 studies in healthy adults aged 18 to 45 (average starting VO2max about 41 ml/kg/min) found that steady endurance training raised VO2max by about 4.9 ml/kg/min compared with people who didn't train. High-intensity interval training raised it by about 5.5 ml/kg/min (6). The gains were larger in people who started less fit and in longer programmes (6). For someone starting at 41, that's an improvement of more than 10%.

These were mostly people new to regular training; if you already train several hours a week, the easy gains are already in the bank. A much larger 2025 analysis of training studies, which looked mainly at changes inside the muscle but also pooled their VO2max results, found the same pattern: the lower someone's starting fitness, the bigger their percentage gain in VO2max (7).

A second meta-analysis of interval programmes in sedentary or recreationally active people, who trained at least three days a week for 6 to 13 weeks, found VO2max rose by about 0.5 litres per minute on average. For a 75 kg person that's about 7 ml/kg/min, and the gains were larger with longer intervals (8).

Not everyone responds the same

The averages hide a lot of variation. In the HERITAGE Family Study, 481 previously sedentary adults followed the same 20-week cycling programme. The average gain was about 0.4 litres per minute, but some people gained little or nothing, while others gained more than 1 litre per minute (9). How much a person improved ran strongly in families: the researchers estimated that up to 47% of the difference in response was heritable (9).

The evidence on sex differences is mixed. A meta-analysis of eight small studies that gave untrained men and women the same training found larger gains in men, by about 2 ml/kg/min on average (10). The much larger 2025 analysis found that women gained more in percentage terms (7). The two differ a lot in size and design, and on balance sex isn't a reason to expect less from your training.

If your VO2max rises slowly, it doesn't necessarily mean you're training wrongly; you may simply respond less in this one measure. You can still get faster, because training also improves how your muscles work below your maximum (1).

Which training raises VO2max most

Steady training raises VO2max, especially when you're starting out (6). Intervals raise it at least as much, and their details matter.

A meta-analysis of 53 randomised trials compared different kinds of high-intensity interval training (11). Programmes built on short intervals of 30 seconds or less, on five minutes or less of hard work per session, or lasting four weeks or less all improved VO2max compared with no training. The larger gains, though, came from each of these:

• long intervals, of two minutes or more,
• more hard work per session, 15 minutes or more in total, and
• longer programmes, of 4 to 12 weeks or more.

Compared with moderate continuous training, only long-interval, higher-volume and longer programmes showed a clear extra benefit (11). How often you train matters too: in the 2025 analysis, more sessions per week went with bigger VO2max gains (7).

If you're already well trained

A review of highly trained endurance athletes concluded that adding more easy volume doesn't appear to further raise their VO2peak (the highest oxygen uptake reached in a test) or their performance, and that, in the studies available then, further performance gains came from high-intensity interval training (12). A meta-analysis of nine small studies in national-level athletes from a range of sports found that interval training raised VO2max more than conventional training did (13).

Both are small bodies of evidence in athletes training far more than most amateurs. On 5 to 15 hours a week you sit in between: more volume and threshold work still make you faster, and intervals are one tool among several.

How to use this in your training

If you're new to structured training, steps 1, 3 and 7 matter most. If you already train a lot, expect the smaller gains described above and treat this as one block in your season.

1. Build on steady aerobic work. Most of your training should stay easy. Steady aerobic work raises VO2max when you're starting out (6) and improves how your muscles work below your maximum (1). The hard sessions below work best on top of that base, which also protects you from doing too much intensity too soon.

2. Do one long-interval session a week. It should match what the evidence favours: repetitions of at least two minutes, building up to at least 15 minutes of hard work (11). Two examples:

• Run: after a 15-minute easy warm-up with a few short strides, 5 × 4 minutes hard with 3 minutes of easy jogging between, then 10 minutes easy.
• Ride: after a 15-minute warm-up, 5 × 4 minutes hard with 4 minutes of easy spinning between, then 10 minutes easy.

For runners, "hard" means about the pace you could race 3 km at, a little faster than your 5 km race pace. Jack Daniels calls this interval (I) pace and sets it from your VDOT, a running fitness score worked out from a recent race result (14). On the bike, it's roughly 106 to 120% of your FTP, or functional threshold power, the highest power you can sustain for about an hour (15). That's a wide range, and where you sit in it depends on you and how your FTP was tested; for 4-minute repetitions, start in the lower half. Don't know your 3 km pace or FTP? Go by feel: hard but controlled, at an effort you could repeat for every repetition. By the end of each repetition it should feel very hard, around 8 to 9 out of 10, with breathing heavy and speech down to a word or two. Your last repetition should be as fast as your first; if it isn't, start slower next time.

3. Build up to it, within your running limit. If you haven't done intervals like this before, start with 4 × 3 minutes and add a repetition or a minute each week. As a rough coaching guide, Daniels caps a session's I-pace running at about 8% of your weekly distance (14). 5 × 4 minutes is roughly 4 to 5 km, so if you run less than about 50 to 60 km a week, stop at fewer repetitions or do the full session on the bike. It isn't a safety limit; your training history and injury record matter more. As a rule of thumb, end the session early if your pace or power drops more than about 5% below your first repetition, or if your form breaks down. Stopping early is the session working as intended, not a failure.

4. Count it once, not per sport. One session a week means one in total. It replaces one of your existing hard sessions in that sport; if you already do two, keep the threshold one. Your long easy sessions stay as they are. Triathletes should pick one discipline each week; the bike is the gentler choice if you're injury-prone, because it puts far less impact on your legs. The interval studies above trained three or more days a week (8), and more sessions went with bigger gains (7), so a single weekly session is a conservative choice. Expect gains on the smaller side.

5. A shorter alternative. Short intervals improve VO2max too, just less than long ones (11). On a busy day, after the same warm-up, do 10 × 30 seconds hard with 30 seconds easy. "Hard" here is a little faster than your 4-minute pace, but still controlled, not an all-out sprint.

6. Give it time, and measure the right thing. The larger gains in the studies came from programmes of 4 to 12 weeks or more (11). Run a block of six to eight weeks. Before and after it, repeat the same benchmark after the same warm-up, on a rested day, in similar conditions: a 5 km time trial, a 20-minute bike test, or your average pace or power across the same interval session. If you're training for races longer than about two hours, do this block early in the season. Once your race-specific build starts, race-pace and threshold work usually take its place.

7. Recover between hard days. Leave at least one easy day after an interval session, and don't put it the day before your long run or ride. Skip it if you're ill, have slept badly for several nights, or your morning HRV (heart rate variability) has sat below your usual range for a few days; one low reading on its own isn't a reason to skip. Tito can build sessions like these into your plan and suggest an easier week when your recovery readings dip. Treat that as a prompt to check how you feel, not a medical verdict.

Before you start: if you're new to hard exercise, have a heart condition, or feel chest pain, unusual breathlessness or dizziness when you exert yourself, see a doctor before adding maximal efforts.

References

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