VO₂max has become one of the most talked-about health metrics of the past few years. Smartwatches estimate it on your wrist. Longevity medicine treats it as a headline number, discussed by a growing list of voices as one of the strongest predictors of how long — and how well — we live. Social media has done what social media does: turned a physiological measurement into a badge.
The training has followed. VO₂max intervals — hard, uncomfortable, unmistakably "high intensity" — have taken on a status that base endurance work never gets. Long, easy aerobic sessions have quietly become the thing you apologise for, while all-out efforts get filmed and shared.
So the question is worth asking plainly: is VO₂max really one of the best measures of health we have — or just another fitness trend that's found its moment?
As so often, the answer isn't something you can summarise in a single sentence. To understand it, we first need to understand what VO₂max can tell us — and what it can't.
What does VO₂max actually measure?
VO₂max stands for maximal oxygen uptake — the maximum rate at which your body can take up, transport and use oxygen during maximal exercise.
You'll usually see it reported in litres per minute (absolute) or millilitres per kilogram per minute (relative). The relative value is often more useful for comparing people, since it accounts for body size.
VO₂max reflects the integrated function of multiple systems working together: the lungs taking in oxygen, the heart and blood delivering it, the vessels distributing it, and the muscles and mitochondria using it to produce energy.
That's part of why it's such a compelling number — a measure of how well the whole chain works, from the air you breathe to the energy your cells produce. It's the same integrated system we talked about in the cardiovascular training article — VO₂max reflects the upper limit of that integrated system's capacity.
Why do we care so much about it?
The scientific interest in VO₂max isn't just another passing trend. Higher cardiorespiratory fitness is consistently associated with a lower risk of cardiovascular disease, lower all-cause mortality, healthier ageing, and maintaining physical independence for longer.
This doesn't mean that VO₂max itself protects us from disease. Rather, it reflects a collection of physiological adaptations associated with a more resilient cardiovascular and metabolic system. When the body can efficiently deliver and use oxygen under high demand, recovery from physical stress is generally better. People with a high VO₂max are also typically better prepared for the demands of ageing and are statistically less likely to develop many common chronic diseases.
This is where physiological reserve becomes useful — a concept I think deserves far more attention than it gets. We should aim for something much more long-term, even if the benefits aren't immediately visible. We should train so that the demands of everyday life twenty or thirty years from now occupy only a small proportion of our maximal capacity. The stairs don't change — you do. Climbing a flight at 40 might use 20% of your capacity. If that capacity declines, the same flight at 80 might use 90% of what's left. Train well over those decades, and it might still only cost you 40%.
That's the real promise of VO₂max training. Not a better number today. A larger buffer for the rest of your life.
Can you improve your VO₂max?
Yes — and for most people, by more than they'd expect.
Genetics do play a role, influencing your starting point, your upper limit, and how responsive you are to training. But here's the encouraging part: most people are nowhere near their physiological potential. They're simply closer to their current lifestyle than to their genetic ceiling. In other words, most people are nowhere near being limited by their genetics.
Previously untrained individuals commonly see substantial gains after several months of structured endurance training, though individual responses vary widely. Highly trained athletes, already close to their own ceiling, often spend months chasing improvements of only a few percent.
The goal isn't to reach someone else's genetic potential. It's to get much closer to your own — and hold onto it as you age. VO₂max naturally declines over the decades if left untrained, so the real win isn't a single peak number. It's staying as close to your ceiling as possible, for as long as possible.
How do we improve it?
This question has increasingly become a "Zone 2 vs. HIIT" debate. I think that's as unhelpful as asking whether strength or cardio matters more. Different types of training create different physiological adaptations, and a well-built programme uses more than one.
Zone 2 training increases mitochondrial content, oxidative enzyme activity, and capillary density — the infrastructure that allows your muscles to extract and use oxygen efficiently.
Higher-intensity training drives central cardiovascular adaptations: stroke volume and maximal cardiac output — your heart's capacity to move oxygenated blood under real demand.
Strength training can improve neuromuscular efficiency and, depending on the activity, movement economy — helping you produce the same work with less oxygen.
VO₂max reflects a team effort. Zone 2 improves your muscles' ability to use oxygen. High-intensity training improves your heart's ability to deliver it. Strength training helps you get more out of the oxygen that's delivered. None of them replace the others.
What VO₂max does not tell us
Two people can have identical VO₂max values and perform completely differently. VO₂max measures capacity — not lactate threshold, exercise economy, fuelling, pacing, technical skill, or the mental side of pushing hard. It measures potential, not performance.
And even VO₂max itself isn't measured in isolation from the person. A maximal test also requires a willingness to truly reach your limit. Motivation, experience and even the testing environment can therefore influence how accurately it reflects your true physiological capacity.
Finally, a high VO₂max alone doesn't make someone healthy. Health is never defined by a single number. Blood pressure, sleep, nutrition, metabolic health, and many other factors all contribute to long-term health.
What is a good VO₂max?
There's no universal "good" number — it depends on your age and sex, and lab and smartwatch values aren't directly comparable. Comparing yourself to elite athletes isn't useful either. Your own trend over time matters far more than any single benchmark. A laboratory test will usually show how your VO₂max compares with other people of the same age and sex.
How is VO₂max measured — lab vs. smartwatch
The gold standard is a lab test: a mask, a treadmill or cycle ergometer, and expired gas analysis measuring exactly how much oxygen you use as you're pushed to true maximal effort. It's a direct measurement, and the benchmark everything else is judged against.
Your watch, by contrast, doesn't measure VO₂max directly — it estimates it using algorithms based on factors such as heart rate, pace or speed, and personal characteristics like age, sex, height, and weight. Different devices use different algorithms, so estimates aren't directly comparable between brands. That estimate can also shift with heat, altitude, dehydration, fatigue, or inaccurate heart-rate measurements. As a result, smartwatch estimates often differ substantially from direct laboratory measurements. If you want an accurate measurement of your VO₂max and want to track it over time, regular laboratory testing remains the best option.
So... is VO₂max the GOAT?
For the time being — yes, as a health marker. It's one of the strongest and most consistently validated predictors of long-term health we have, and unlike most of the others, it's one you can actually change through training rather than just monitor.
VO₂max is one of the most valuable health markers we have. But like every single metric, it never tells the whole story. Better decisions don't come from chasing a number — they come from understanding what that number can tell us, and what it can't.