What VO2max measures

VO2max is the most oxygen your body can take in and use during all-out exercise, usually written in millilitres per kilogram of body weight per minute. It reflects how well your heart, lungs, blood and working muscles cooperate when you push hard.

In the FRIEND registry, a US database of 7,783 maximal treadmill tests in healthy adults aged 20–79, VO2max differed by sex and by age group. ² Across five decades of age, it fell by roughly 10% per decade. ² Our tool, Estimate your VO2max, uses those reference values to place your number in context.

That decline is an average across many people, not a schedule you have to follow. Training is the lever you control, and it works at every level, from your first easy runs to your tenth season of hybrid racing.

Why fitness is linked to a longer life

A Cleveland Clinic study followed 122,007 adults who had done a treadmill test for a median of 8.4 years. ¹ Fitness was inversely associated with death from any cause, and after adjustment the least fit group had about five times the risk of the fittest group. ¹

The researchers found no sign of an upper limit. The elite group, the top 2.5% for their age and sex, had a lower risk than the high performers. ¹ Low fitness carried a risk comparable to, or greater than, well-known clinical risk factors such as smoking and diabetes. ¹

This is an observational study, so it shows an association rather than proof that training adds years. It does make a clear case for treating aerobic fitness as a health number worth tracking, alongside blood pressure or body weight.

How to estimate yours

The most accurate measurement is a lab test with gas analysis, where you work to exhaustion on a treadmill or bike while a mask measures the air you breathe. It is precise, but it costs money and time.

A free estimate comes from two numbers you already know. The heart rate ratio method multiplies 15.3 by your maximal heart rate divided by your resting heart rate. ³ It was developed in well-trained men, and its authors noted that other groups still needed direct validation. ³ Our estimator uses it and labels the result as an estimate.

If you do not know your maximal heart rate, a common estimate is 208 minus 0.7 times your age. ⁷ Many sports watches also estimate VO2max from runs or rides with their own methods.

How to raise it: volume and intensity

Your engine grows from two kinds of work. Plenty of easy, steady sessions build the base, and a small dose of hard intervals lifts the ceiling.

A meta-analysis of 28 controlled trials in 723 healthy adults aged roughly 18–45 found that both endurance training and high-intensity interval training produced large improvements in VO2max. ⁵ The gains were somewhat larger after interval training. ⁵

A widely used interval session comes from a Norwegian study. Participants ran four bouts of 4 minutes at 90–95% of maximal heart rate, each followed by 3 minutes of active recovery at about 70%. ⁴ Done three times a week for eight weeks, it raised VO2max by about 7%, significantly more than long slow running or threshold running with the same total work. ⁴

That study was small and included only moderately trained men, so read the exact numbers as a guide rather than a promise. ⁴ The structure travels well: it works on a hill, a bike, a rower or a ski erg.

Pace the first interval so you could do a fifth one if you had to. The aim is four strong, even efforts, not one heroic first round and three survival rounds. If your heart rate drifts above the target band early, slow down; if the last interval feels easy, add a little speed or resistance next time.

Fitting it into your week

The WHO advises 150–300 minutes of moderate activity or 75–150 minutes of vigorous activity a week, or a mix of both, plus muscle-strengthening work on 2 or more days. ⁶ Intervals count as vigorous minutes, so a little goes a long way.

The Norwegian participants did intervals three times a week and little else. ⁴ If you also lift and do Zone 2, one or two hard sessions usually leaves room to recover. Keep the hard days hard and the easy days genuinely easy.

• Starting out: three easy sessions of 30–45 minutes for four to six weeks, then swap one of them for a 4 × 4 session.
• Already training: one 4 × 4 session and one shorter interval session, for example 6–8 × 1 minute hard with 1–2 minutes easy, on top of your Zone 2 and strength days.
• Hybrid race season: keep it to one or two hard sessions a week and count race-pace work as one of them.
• Leave an easy day or a rest day after every hard session.

Measure, train, retest

Retest every 8–12 weeks with the same method. Our estimator only needs your resting and maximal heart rate, so it is easy to repeat under the same conditions: resting heart rate measured lying down, right after waking.

Expect the biggest changes early. In the meta-analysis, people with lower starting fitness and longer programmes saw larger gains from interval training. ⁵ If you are already very fit, smaller numbers still count.

Look beyond the single number too. Easier paces at the same heart rate, a lower morning resting heart rate and faster recovery between intervals are all signs your engine is growing, and they show up in your training log long before the next test.

Hard work, safely

Talk to your doctor before you start interval training if you have a heart condition, chest pain on exertion, high blood pressure that is not under control, or if you have been inactive for a long time.

Stop and seek advice if you feel chest pain, unusual breathlessness, dizziness or palpitations during exercise.

Beta-blockers and some other medicines change heart rate, so heart-rate targets may not fit you. Use effort instead: in a hard interval you should only manage a few words at a time.

Questions people ask