VO₂ max: the number that reads most like a date

If you could know only one number about your health, there is a solid argument for it being this one. It is not a laboratory marker and it does not come from a drop of blood: it comes from running or cycling until you cannot any more, with a mask on.

VO₂ max is the maximum amount of oxygen your body is able to take in, transport and use per unit of time. It is, in practice, the ceiling of your engine. And it turns out that ceiling predicts things.

The study

In 2018, Mandsager and colleagues published a retrospective cohort study in JAMA Network Open with 122,007 patients who had completed a treadmill exercise test at an academic center between 1991 and 2014. Mean age, 53.4 years. Median follow-up, 8.4 years.

The result: cardiorespiratory fitness was inversely associated with all-cause mortality. More fitness, less mortality.

And here is the part that makes this study different from almost everything else: the authors observed no upper limit of benefit. The point beyond which being fitter stopped being associated with living longer did not appear. The extreme fitness group — two standard deviations above the mean for their age and sex — had the lowest risk-adjusted mortality of all the groups compared.

No ceiling appeared. That is the strangest and the most interesting part of the finding.

Why this is not the same as "exercise is good"

Because "exercise" is a behavior and VO₂ max is a measurement. Two people can report the same amount of weekly exercise and have completely different ceilings. And it is the ceiling, not the reported behavior, that appears associated with the outcome.

That makes VO₂ max something unusual in this field: a marker that is both powerful as a predictor and modifiable. Cholesterol can be modified, yes, but you do not train it. This one you train.

The obligatory caution

It is an observational cohort. It shows a very strong and consistent association, not a demonstration of causality. And there is a known problem of direction: low fitness can be a consequence of a disease not yet diagnosed, rather than its cause. Studies adjust for what they can, but the possibility is not eliminated.

Even so, within the evidence available in longevity, it is among the most robust there is: a large sample, an objective measurement — not a questionnaire — and a hard outcome.

What to do with the figure

First, have it. Most people do not know their VO₂ max, which is striking for the number with this track record. It is measured with an exercise test with gas analysis; it is also estimated — less precisely — from submaximal protocols and from some devices.

• Measuring it once gives you a position. Measuring it twice, spaced out in time, gives you a trajectory — and the trajectory tells you more than the isolated value.
• A watch's estimate is useful for following your own trend, not for comparing yourself with anyone.
• It is interpreted by age and sex: the raw number, on its own, does not say whether you are doing well or badly.
• And if there is going to be a maximal test, it is done with prior medical judgment, not out of curiosity.

In PROFIT7's Strategic Movement this number is not a trophy: it is a baseline. It serves to know where the plan starts and to check, later, whether the plan did anything. Without measuring it, the only way to evaluate a training program is to ask yourself how you feel — which is valuable information and, at the same time, insufficient.