VO2 max: the fitness number that predicts lifespan, and how to raise it

VO2 max is the maximum amount of oxygen your body can take in and use during hard exercise. It reflects how well your heart, lungs, blood vessels and muscles work together. And it turns out to be one of the strongest predictors of how long people live.

The evidence

In a study of more than 120,000 people who took treadmill tests, those with the lowest fitness had around five times the risk of death of the fittest over the following years. The effect was larger than that of smoking or diabetes. A later study of 750,000 US veterans found the same pattern: the least fit had about four times the mortality of the most fit, and there was no point at which more fitness stopped helping.

VO2 max also declines with age, roughly 10 % per decade after 30 in people who don't train. The fitter you are in midlife, the more reserve you have for the things that matter in your 70s and 80s: climbing stairs, carrying shopping, travelling on your own.

How to measure it

• A lab test on a treadmill or bike with a mask that measures your breathing. The most accurate, and the one to use at the Optimized level.
• A wearable estimate. Most sports watches estimate VO2 max from your heart rate and pace. They're not precise, but they're consistent enough to track trends.
• The Cooper test. Run or walk as far as you can in 12 minutes on a flat course. Your estimated VO2 max is (distance in metres − 505) ÷ 44.7.

Compare your result with others your age and sex. At the Optimized level in the journal, the target is the top 10 %.

How to raise it

Two kinds of training do most of the work.

1. Zone 2: the base. Steady exercise at an effort where you can still talk in full sentences: brisk uphill walking, easy cycling, a gentle jog. Two or three sessions of 30–60 minutes a week build the heart's pumping capacity and your muscles' ability to use oxygen.

2. Intervals: the ceiling. One hard session a week pushes VO2 max up faster. The best-known protocol is the 4 × 4: four minutes hard (around 85–95 % of your maximum heart rate), then three minutes easy, repeated four times. In a Norwegian study, it improved VO2 max more than steady training of the same total effort.

A simple week: two zone 2 sessions, one 4 × 4, two strength sessions, and daily walking. Untrained people often see meaningful improvements within two to three months.

Start where you are

If you haven't exercised in a while, start with zone 2 only for the first month, and build the time gradually. If you have a heart condition, chest pain on exertion or other risk factors, check with your doctor before adding intervals.

In the journal: cardio is one of the five areas on your fitness map, and VO2 max is an Optimized box. If cardio is your weakest area, "zone 2 done" is a good daily box.

Sources: Mandsager et al., JAMA Network Open 2018 · Kokkinos et al., Journal of the American College of Cardiology 2022 · Helgerud et al., Medicine & Science in Sports & Exercise 2007.