Knowing your maximal aerobic capacity -- referred to as VO2 max -- is useful for tracking fitness level and choosing workouts that are the right intensity to meet your goals. Direct measurement of VO2 max requires a testing facility with specialized equipment and trained personnel. You work out at a gradually increasing intensity until you reach your maximum physical effort. This is uncomfortable for most and potentially dangerous for those who are out of shape or have medical problems. An alternative to direct VO2 max measurement is VO2 max estimation with a sub-maximal aerobic fitness testing, which is less risky and requires less physical effort.
During a sub-maximal aerobic fitness test, heart rate or distance covered is used to estimate VO2 max. Unlike direct VO2 max measurement, during a sub-maximal test the heart rate should not rise above a pre-determined maximum -- usually 85 percent of the estimated maximal heart rate based on age. While sub-maximal graded exercise tests are usually done in a laboratory or gym setting under professional supervision, several sub-maximal field tests can be done on your own with a timer and/or a heart rate monitor.
Graded Exercise Tests
Graded exercise tests consist of multiple stages of increasing effort until you reach the pre-determined maximum heart rate or cannot continue any longer. Sub-maximal testing can be done using a protocol similar to that of the VO2 max test but stopping before you reach your maximum physical effort. Other tests, such as the YMCA Sub-maximal Cycle Test or a sub-maximal treadmill test, can be done in a gym. Although the protocols for these tests are not as strict as for laboratory testing, they usually still require professional supervision.
There are many different sub-maximal field tests, with differences in type of exercise, duration of test and method for VO2 max estimation. Running, walking and jogging field tests can be divided into two categories: fixed time and fixed distance. The Cooper 12-Minute Run Test and the 6-Minute Walk Test are examples of fixed-time tests that use the distance covered during the allotted time to estimate VO2 max. The Cooper 1.5 Mile Test, the Rockport Walking Test and other fixed-distance tests use the time taken to cover the specified distance to estimate VO2 max. The advantages of these tests are that you can do many on your own; they require only a stopwatch or heart rate monitor and they can be done in a gym or outdoors, provided you have a way to measure distance.
VO2 max is a good indicator of fitness level, but it changes over time with changes in the frequency or intensity of aerobic exercise. For this reason, experts recommend periodic VO2 max measurement or estimation for individuals who want to track aerobic capacity. Unless you are a competitive athlete or a regular participant in endurance sports, the greater accuracy of direct VO2 max testing probably does not outweigh the cost, inconvenience and physical stress compared to VO2 max estimation by sub-maximal testing.