VO2 Max which is also written as ‘Volume O2 Max’, indicates the highest amount of oxygen that one can use during very strenuous physical exercise also known as cardiopulmonary exercise, and is stated in milliliters of oxygen per kg of body mass and per minute. Endurance athletes, such as cross-country skiers, long distance runners or cyclists need it because it shows how much work they can sustain. Even for common people who strive to lead active and healthy life, a high VO2 Max is said to represent good cardiovascular fitness and endurance.