VO2 Max

VO2 Max is the maximum rate at which your body can take in and use oxygen during exercise, written in milliliters of oxygen per kilogram of body weight per minute. It is the most widely used single measure of aerobic fitness, and it predicts endurance performance better than almost anything else that can be measured in one test.

A real measurement involves a mask, a treadmill or a bike, and an effort taken to exhaustion. What your watch reports is an estimate, worked out from the relationship between your heart rate and your pace or power over many sessions: if you are going faster at the same heart rate than you were a month ago, your estimate goes up.

It responds to training over months rather than weeks, and it is partly inherited. The useful question is not how your figure compares with somebody else's but whether it is moving in the direction you want over a season.

What it is not

An estimate from a wrist device is not a laboratory measurement, and the two can differ by several points. It is also not a verdict on your health or a prediction about your lifespan, whatever a fitness age derived from it may suggest.

Where you see it in FitnessSyncer

A VO2 Max that arrives from a connected service is charted over time on your Dashboard, and our fitness age calculator turns a reading into a fitness category and a fitness age.