VO2 max is your maximal oxygen consumption as measured during cumulative exercise, and is usually conveyed in milliliters of oxygen per kilogram of body weight per minute, when comparing the performance of endurance sports athletes. VO2 max varies from athlete to athlete, and is the absolute best measurement of cardiovascular fitness. VO2 max may also be known as maximal oxygen consumption, maximal oxygen uptake, peak oxygen uptake or maximal aerobic capacity.