Oxygen consumption (VO2) can be measured in a variety of ways to express energy expenditure. The first (VO2 (L∙min-1)), is measuring liters of oxygen consumed per minute. The second (VO2 (ml∙kg-1∙min-1)), is measuring milliliters of oxygen consumed per kilogram of body weight per minute. This may also be referred to as relative VO2. The latter can be used to compare two values between people of different body size. When referring to activities such as walking and running, relative VO2 is commonly used because they are weight bearing activities1.