VO2max — the number that predicts how long you'll live

VO2max is the maximum amount of oxygen your body can take in and use at peak effort. Roughly speaking, it's the "engine power" of your cardiovascular and respiratory systems. The higher it is, the more easily your body handles both a flight of stairs and an illness.

What 122,000 people revealed

In 2018, JAMA Network Open published one of the largest studies on the subject (Mandsager and colleagues): more than 122,000 patients underwent a treadmill stress test and were then followed for years. The result is unambiguous: the higher the cardiorespiratory fitness, the lower the risk of death from all causes — and with no visible upper limit on the benefit.

The biggest gap was between the bottom 25% (low fitness) and everyone else. In other words, moving from a "completely unfit" state to even an "average" one delivers the largest gain. And people with extremely high fitness (two standard deviations above the norm for their age and sex) had the lowest mortality of all.

Why it matters more than many lab tests

Unlike genetics, VO2max is a trainable parameter. The study's authors stressed that low cardio fitness carries a risk comparable to smoking, diabetes or high blood pressure. But while blood pressure and blood sugar are usually treated with pills, fitness grows from plain, ordinary physical activity.

How to raise your VO2max

The foundation is regular aerobic activity at an easy pace ("zone 2"): jogging, brisk uphill walking, cycling, rowing — at a heart rate where you can still hold a conversation. That volume builds your mitochondrial base. On top of it you add a small amount of high-intensity intervals, which effectively lift the VO2max ceiling itself. The combination of long and easy plus short and intense is the working formula.

What "zone 2" means in plain terms

Zone 2 is an intensity at which you can keep a conversation going but already with mild breathlessness; singing — no, speaking in full sentences — yes. At that heart rate the body mainly burns fat for fuel and builds the number and efficiency of its mitochondria — the cells' "power plants." It's precisely this easy base that makes harder work possible and improves everyday endurance. A common beginner mistake is to "go all out" in every session: that drains you faster and builds the base worse than combining high-volume easy work with occasional hard efforts.

How much and how often

The standard physical-activity guidelines — around 150 minutes of moderate aerobic activity per week — are a sensible target for the base. In practice that means, for example, a few easy sessions of 30–45 minutes plus one short interval session per week. Progress is measurable: over time the same pace comes at a lower heart rate, and familiar efforts stop leaving you out of breath. It's never too late to start — and, judging by the data, it's the least fit for whom every step yields the biggest gain.