The ideal method of measuring oxygen consumption (VO2) uses gas analyzers with higher levels of measurement accuracy. This is called the benchmark. VO2max has traditionally been measured while the athlete runs on a treadmill or pedal on a cycle ergometer, with the intensity of the exercise increasing progressively, until it reaches voluntary exhaustion. The expired air is collected in the test, and the oxygen consumption is calculated. The maximum value reached is VO2max. Currently, the availability of portable gas analyzers (including breath-by-breath analysis equipment) makes oxygen consumption tests more agile and specific.
The high cost of these devices, the need for specialized personnel for their handling and a great deal of time in their use, makes impractical direct measurements of VO2max to study large populations. Considering these barriers for using direct measurements of VO2max, indirect methods using equations have been elaborated to estimate the VO2max, from simple measurements such as distance traveled, speed reached, time spent in the test and heart rate.
There are several so-called “indirect” tests, and in particular three of them have been widely applied to estimate VO2max: the 20-meter “Shutle run” test, Cooper’s 12-minute test, and lactate threshold. They show high correlation when compared to the test performed in a treadmill with gradual increase of speed and direct measurements using gas analyzers.
20-meter “Shutle run”
The “Shutle run” test was introduced by Léger in a paper from 1988. The athlete runs back and forth on a 20 m course. The athlete must touch the 20 m line at the same time a pre-recorded sound. The pace is controlled by the frequency of the sound signals, which are recorded to increase the pace at pre-established levels by 0.5 Km/h increments. When the athlete can no longer follow the pace, the last stage number is used to predict maximal oxygen uptake (VO2max). It considers the speed corresponding to that stage and age to calculate the VO2max. There are several variations of this method.
Cooper Run Test (CRT)
Cooper Run Test (CRT) is a popular method based on the book Aerobics by Dr. Kenneth Cooper from 1968. It is a simple method that aims to determine the distance covered in 12 minutes of running and/or walking. The result is then used to indirectly estimate VO2max.
Lactate Threshold (LT)
It is an anaerobic test in which blood samples are collected at intervals during an incremental exercise test. Lactate accumulates in the blood during exercise and it is a good marker for fatigue and a way to indirectly estimate VO2max.