VO2 max test: what it costs and what the evidence says

VO2 max is the most oxygen your body can use during hard exercise. It is a measure of how fit your heart and lungs are. In a lab test you pedal a bike, or walk or run on a treadmill, and it gets harder until you cannot go on. You wear a mask that measures the air you breathe in and out, and staff track your heart with an ECG. Hospitals call this a cardiopulmonary exercise test, or CPET (Royal Devon NHS).

Lab test or watch estimate. Many sports watches show a VO2 max figure. They estimate it with a formula; they do not measure the air you breathe. A 2022 review found that watch estimates made during exercise were close on average across groups of people, but could be far off for one person. Estimates made at rest tended to be too high. The American Heart Association calls the lab test with a mask the "gold standard". It says estimates made without an exercise test should not replace a real test.

Safety. The test means working as hard as you can. NHS patient information says serious problems are rare, and that staff stop the test if warning signs appear (East Lancashire NHS). People who have had a recent heart attack or stroke, or a recent illness, may need to wait or may not be able to have it.