VO2 max explained: what is a good score and how to improve it

VO2 max is the maximum amount of oxygen your body can take in and use during all-out exercise. The name is literal: V for volume, O2 for oxygen, max for the ceiling. It is measured in milliliters of oxygen per kilogram of body weight per minute, written ml/kg/min. The higher the number, the more oxygen your heart, lungs, blood, and muscles can move and burn together when you push hard.

That makes VO2 max the single best summary of cardiorespiratory fitness. It is not one organ's job. It reflects how strongly your heart pumps, how much oxygen your blood carries, and how well your working muscles pull oxygen out and turn it into energy. When any link in that chain gets stronger, the number climbs. That is why endurance athletes post the highest values and why a fitter version of you, a year of training later, will measure higher than you do today.

It is also one of the most powerful health markers known, well beyond sport. Cardiorespiratory fitness is one of the strongest predictors of all-cause mortality in the research literature. Large studies have found the least-fit groups carry several times the mortality risk of the fittest, and that low fitness is associated with greater risk than several traditional risk factors. A higher VO2 max does not guarantee a longer life, but as a marker, very few track long-term health as closely. For that reason it sits at the center of both performance training and longevity thinking.

There is no single good number, because a good VO2 max depends on your age and sex. Values are highest in your 20s and 30s and drift down from there, and at any given age men tend to measure a few points higher than women, largely due to differences in body composition and blood oxygen-carrying capacity. So the only honest way to read your score is against an age-and-sex chart.

As a rough orientation: a man in his 30s is in excellent shape above roughly 49 ml/kg/min, in his 40s above about 45, and in his 50s above about 41. A woman in her 30s is excellent above roughly 41 ml/kg/min, in her 40s above about 38, and in her 50s above about 35. The good range sits a few points below excellent at each step, and the average person lands lower still. Use these as signposts, not hard cutoffs. Hitting the good-to-excellent band for your own age and sex is a strong place to be.

One important caveat if your number comes from a wearable: it is an estimate. Apple Watch, Garmin, and similar devices infer VO2 max from your heart rate, pace or power, age, and weight, so any single reading can sit several points off a proper lab test on a treadmill with a metabolic cart. Do not treat a watch figure as a precise medical value. Treat it as an approximate snapshot whose real value shows up over time, which is the next section's point.

VO2 max responds to training, and the most reliable approach pairs two ingredients: hard intervals to lift the ceiling, and a large easy aerobic base to support them. Neither works as well alone.

The sharpest tool is high-intensity interval training. Repeated efforts of roughly two to four minutes at near-maximal effort, each followed by easy recovery, push your cardiovascular system to its oxygen ceiling and signal it to raise that ceiling. Two such sessions a week is plenty for most people. These are the workouts that move the number fastest, but fastest still means weeks of consistency, not days, and they are demanding enough that more is not better.

The quieter half of the work is a big zone 2 aerobic base: easy, conversational-pace running, cycling, rowing, or brisk walking where you could still hold a conversation. This lower-intensity volume builds the underlying machinery (capillaries, mitochondria, stroke volume) that lets your body deliver and use oxygen efficiently, and it is what makes hard intervals productive rather than just exhausting. A common, sustainable balance is the majority of your weekly minutes easy and a small slice hard. Build the base, sprinkle in the intervals, stay consistent across months, and the trend line moves.