Define Measuring Direct Aerobic Fitness (VO₂ max)

For direct measurement of VO, max, the subject is asked to perform exercise for 12 to 15 minutes. A stationary bicycle or a treadmill is typically used. The test starts with a moderate work load which is maintained for a few minutes. The load is increased gradually every few minutes until reaching the maximum level that the subject can tolerate. This is done by increasing the cycling resistance or the speed and grade of the treadmill. The oxygen uptake measured at the maximal load is the subject's VO₂ max. The subject works until VO₂ max is reached, indicated by max heart rate, VO2 max plateau (or over peak), respiratory exchange ratio of 1.15 (or greater) or voluntary exhaustion.

The higher the VO₂ max, the more work one can perform; thus, better the level of aerobic fitness. The disadvantage of these laboratory methods to determine aerobic fitness is that these require maximal work till exhaustion and are expensive. The advantage of this method is that it is most accurate to indicate aerobic capacity. VO₂ max ratings can be accessed from Table for men and Table for women.