What indicates that a valid VO2 max has been reached?

A valid VO2 max is indicated when there is a plateau in O2 uptake during an incremental exercise test, despite an increase in exercise intensity. This plateau signifies that the individual's oxygen consumption has reached its maximum capacity, meaning the body can no longer take in and utilize more oxygen to produce energy for physical activity.

This physiological response is critical in determining the VO2 max, as it reflects the point at which the cardiovascular and respiratory systems are fully stressed and cannot increase oxygen delivery further, despite increased exercise intensity. The attainment of a plateau demonstrates that the subject has truly reached their maximal aerobic capacity, ensuring the test results are valid and reliable.

While maximal heart rate, a high respiratory quotient, or a high rating of perceived exertion can provide supporting evidence that an individual is working hard, they do not definitively indicate that the VO2 max has been reached in the scientific sense. Therefore, the presence of a plateau in O2 uptake serves as the primary criterion for validating an individual's VO2 max.