VO2 max, also known as maximum aerobic power or aerobic capacity, is defined as the measurement of the most oxygen a human can use when exercising as hard as possible. When the intensity of the exercise increases, but the amount of oxygen used remains the same, the VO2 max has been reached. This maximum aerobic capacity is often used as a predictor for athletic performance, but cannot be directly correlated to success. For example, a marathon runner with a high VO2 max level will not necessarily outrun his competitors with lower levels, as the top running speed at which each reaches his maximum may be different.
The V in VO2 stands for the rate of ventilation. This measurement is expressed in milliliters of oxygen consumed per kilogram of body weight per minute. Also, the term is correctly written with a subscripted O2 for oxygen, but most publications simply list it as O2 for convenience.
VO2 max can also be measured using body surface area. This can produce a larger difference in results between the general population and trained athletes than when weight is used. Aerobic capacity also varies across the sexes, as males typically use 20 to 25 percent more oxygen at maximum effort than do females; however, this gap closes to about 10 percent when comparing elite athletes.
Tests used to measure VO2 max are typically estimates as finding an exact number requires equipment to measure the gas composition of air being inhaled and exhaled during an exercise test. A common example of a test used to estimate aerobic power is the Cooper 12-minute run. The test is a warm-up followed by 12 continuous minutes of running around a track with a known distance. When the 12 minutes are up, the distance covered is multiplied by 0.0225 for meters or 0.0206 for yards. Then, 11.3 is subtracted from that number; the result is an estimated VO2 max.
To increase VO2 max, a regimen of regular aerobic exercise is recommended, though results vary significantly for different age groups as well as for the different sexes. Short burst or interval training has been shown to have little to no effect in increasing maximum oxygen uptake. VO2 max can be an excellent predictor of athletic performance and general health, and is often used as a physical test requirement for police services and other agencies which require a high degree of physical fitness.