VO2 Max is a measure of how fit a person is. It is a measurement of how much oxygen your body is able to use while exercising at the highest intensity you can. It's a way of figuring out how much work your body can do in a certain amount of time. The higher your VO2 Max, the more work your body can do and the more fit you are. You can find out your VO2 Max by doing special tests at the doctor's office or gym.