VO₂max is the strongest predictor of how long you live. Here is the evidence.

If you could measure one thing about your body and act on it, aerobic capacity is the one with the strongest evidence behind it. Not cholesterol, not weight, not blood pressure. The number is VO₂max, and it moves.

The Cleveland Clinic cohort

Mandsager and colleagues followed 122,007 adults who had done a treadmill test between 1991 and 2014. Fitness was inversely associated with mortality across the whole range, with no ceiling: the elite group had about 80% lower risk of death than the least fit, and even "above average" carried an 84% higher risk than "elite". Low fitness was comparable to, or worse than, coronary disease, diabetes and smoking as a risk factor.

That is an observational study, so it cannot prove that raising your VO₂max lowers your risk. But the dose-response is steep and consistent across sex, age and existing disease, and it agrees with every other large cohort that has looked.

Why aerobic capacity is so predictive

VO₂max is the ceiling on how much oxygen your body can deliver and use per minute. It integrates the heart's stroke volume, the lungs, blood volume, capillary density and the mitochondria in your muscles. A high number means every one of those systems is in good order, which is why it predicts outcomes that have nothing to do with running.

It declines, and the decline is optional

Untrained adults lose roughly 10% of VO₂max per decade after thirty, accelerating later. Trained adults lose much less. Because the number responds to training within weeks, and because a lab test is expensive, the practical approach is a repeatable field estimate every six weeks or so, tracked as a trend.

How PeakVital measures it

PeakVital estimates VO₂max from a guided walk-run protocol, or takes the value straight from your wearable if it already reports one, scores it against your age and sex, and folds it with two other tests into a single Vital age. The point is not the lab-grade number; it is a number you can measure the same way every six weeks and watch move.