Define VO2 max.

VO2 max represents the maximum rate of oxygen consumption measured during incremental exercise, which is a crucial indicator of an individual's aerobic fitness and cardiovascular endurance. It reflects the efficiency with which the body can transport and utilize oxygen during intense physical activity. This measurement is typically assessed using a graded exercise test, where the intensity increases progressively until exhaustion.

Achieving a high VO2 max signifies that the heart, lungs, and muscles are working effectively together to sustain high levels of exercise. This metric is essential in various fields, including sports performance, rehabilitation, and health assessments, as it provides valuable information regarding an individual's cardiovascular capacity and overall fitness level.

The other options provided do not accurately describe VO2 max. The minimum oxygen needed at rest refers to baseline metabolic activity, while average oxygen consumption during steady-state exercise does not account for the peak performance level. Lastly, the total energy expenditure over a 24-hour period encompasses a broader range of activities and metabolic processes beyond just oxygen consumption during exercise.