The a-vO2 diff and cardiac output are the main factors that allow variation in the body's total oxygen consumption, and are important in measuring VO2.
During intense exercise, however, the a-vO2 diff can increase to as much as 16 mL/100 mL due to the working muscles extracting far more oxygen from the blood than they do at rest.
[citation needed] This is a result of aerobic exercise leading to hypertrophy of the slow twitch muscle fibres mainly due to increased capillarisation.
[3] However it has also been found that the increase in the maximal a-vO2 diff resulting from adaptations to a physical training program can account for most of the difference in VO2 max in subjects participating in sub-maximal exercise.
For example, the a-vO2 diff has been used to measure cerebral blood flow in comatose patients, assisting with their diagnosis and treatment.