VO2 Max: The Science of Endurance's Most Important Number

Ask any endurance coach for one number that captures an athlete’s engine, and most will say VO2 max. It is the maximum rate at which the body can take in, transport and use oxygen during hard exercise, usually expressed in millilitres of oxygen per kilogram of body weight per minute. A sedentary adult might sit around 30 to 40. A good club runner can reach the high 50s. The very best endurance athletes on the planet live in a rarefied band above 80. The number is famous for good reason, but the science around it is more nuanced than the headline figure suggests, and the people chasing it at the top of the sport know that better than anyone.

What VO2 max actually measures

The classic definition comes from the work of A.V. Hill in the 1920s, and the underlying physiology has held up well. To use oxygen at a high rate you need to move a lot of air, pump a lot of blood, carry a lot of oxygen in that blood, and have muscles capable of extracting and burning it. The biggest single limiter in most trained people is cardiac output, specifically how much blood the heart can move per beat, the stroke volume. This is why endurance training enlarges the left ventricle and why the trait is so trainable in the heart, even when the lungs are not the bottleneck.

A proper test is done in a lab on a treadmill or bike with a mask that samples expired air while the workload climbs to exhaustion. VO2 max is reached when oxygen uptake plateaus despite increasing effort. Many consumer watches now estimate it from heart rate and pace, which is useful for tracking trends but should not be confused with a true graded test. The estimate can drift by several points.

How the best in the world push it

The athletes at the front of endurance sport combine extreme genetics with decades of structured work. Norwegian runner Jakob Ingebrigtsen and his brothers have reportedly tested in the mid to high 70s, and the so-called Norwegian method built around controlled, lactate-guided threshold sessions has spread through distance running because it lets athletes accumulate large volumes of quality work without breaking down. Tour de France winner Tadej Pogacar has never released an official figure, but credible reporting from sports scientists who have worked with WorldTour riders places elite Grand Tour contenders in the 80s.

Cross-country skiers tend to post the highest numbers ever recorded, because the sport loads both the upper and lower body and rewards a vast aerobic engine. The Norwegian skier Bjorn Daehlie was famously reported around 90, and figures in that region appear repeatedly in Scandinavian testing data. The common thread is not a single magic session. It is years of high aerobic volume, smart use of intervals at or near VO2 max intensity, and the patience to let the heart and blood adapt. Work on the trainability of the trait, including research summarised by the Journal of Applied Physiology, shows large individual variation in how much people respond to the same training.

Trainability versus genetics

This is where honesty matters. VO2 max is highly trainable, but the ceiling is strongly influenced by genetics. The HERITAGE Family Study, one of the most important investigations in the field, found that the response to a standardised endurance programme varied enormously between individuals, and that much of that variation clustered within families. Some people gained little, some gained a great deal, on identical training.

For a recreational athlete the practical message is encouraging. Most untrained adults can raise VO2 max by roughly 15 to 20 percent with consistent training over months, and the gains come fastest early on. For an aspiring elite the message is more sobering. Reaching the 80s almost certainly requires a genetic gift that no training plan can manufacture. Training turns potential into performance, but it does not rewrite the potential itself. The interesting frontier in elite sport is therefore less about raising VO2 max by a few points and more about what happens at submaximal intensities, which is where most races are actually decided.

Why the threshold often matters more

A high VO2 max gets an athlete into the conversation, but it rarely wins the race on its own. Two runners with identical VO2 max values can perform very differently because of their lactate threshold, the intensity at which lactate begins to accumulate faster than the body can clear it, and their running or cycling economy, which is how much oxygen they burn at a given speed or power. An athlete who can hold a high percentage of VO2 max for a long time, and who wastes little energy doing it, beats a bigger engine that runs hot and inefficient.

This is why so much modern endurance training is organised around threshold work and economy rather than maximal efforts. The Norwegian double-threshold approach, lactate testing in training, and careful control of intensity distribution all aim at the same target: raising the sustainable fraction of that maximum. VO2 max is the size of the fuel tank. Threshold and economy decide how far the car goes on it. This interplay also connects to the question of extending athletic careers, since efficiency tends to hold up better with age than raw maximal capacity.

The longevity connection

The most striking research of the last decade is not about racing at all. Cardiorespiratory fitness, which VO2 max captures directly, is one of the strongest predictors of how long a person lives. A large analysis published in JAMA Network Open by researchers at the Cleveland Clinic followed more than 120,000 people undergoing treadmill testing and found that higher fitness was associated with substantially lower mortality, with the benefit continuing to rise across the fitness spectrum. The least fit faced a risk of death comparable to, or worse than, established conditions like diabetes and smoking.

That reframes VO2 max from a niche performance metric into something closer to a vital sign. You do not need an elite number to benefit. Moving from the bottom fitness category to merely below average produced some of the largest reductions in risk in that data. For most people the actionable point is simple. Regular aerobic exercise raises VO2 max, and a higher VO2 max travels with a longer, healthier life. The pursuit that obsesses Tour de France contenders turns out to matter, in a quieter way, for everyone.

FAQ

What is a good VO2 max? It depends heavily on age and sex. For a healthy adult, values in the mid 40s to 50s are good and well above average. Trained endurance athletes often sit in the 60s, and world-class endurance specialists reach the 80s. Cross-country skiers and elite cyclists hold the highest recorded values. For health rather than performance, simply being above the lowest fitness band carries most of the longevity benefit.

Can you really improve your VO2 max, or is it all genetics? Both are true. Most people can raise their VO2 max by roughly 15 to 20 percent with consistent endurance training, and untrained individuals improve fastest. But the ultimate ceiling is strongly genetic, as the HERITAGE Family Study showed, with large differences in how individuals respond to identical programmes. Training realises your potential rather than expanding it without limit.

Is the VO2 max on my smartwatch accurate? It is an estimate, not a measurement. Watches infer VO2 max from heart rate and pace using algorithms, which makes them reasonable for tracking your own trend over time but unreliable as an absolute figure. A true value requires a graded exercise test with gas analysis in a lab.

Sources

1. Cardiorespiratory fitness and long-term mortality – JAMA Network Open, Cleveland Clinic
2. Genomic predictors of trainability and VO2 max response – Journal of Applied Physiology
3. The HERITAGE Family Study overview – Pennington Biomedical Research Center
4. Importance of assessing cardiorespiratory fitness in clinical practice – American Heart Association
5. Factors limiting maximal oxygen uptake – British Journal of Sports Medicine
6. Training intensity distribution in elite endurance athletes – Frontiers in Physiology