Maximal oxygen uptake (VO2 max)

Maximal oxygen uptake (VO2 max) is the highest rate at which the body can take up, transport and use oxygen.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 38.} It depends on maximum cardiac output and the working muscles’ ability to extract oxygen from blood and use it to make energy aerobically.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 38.} ACSM treats it as the criterion measure of cardiorespiratory fitness, usually expressed relative to body mass in mL/kg/min to compare people of different sizes.^{2Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 199.}

Average VO2 max is around 35 to 45 mL/kg/min; elite endurance athletes can reach 80 or more, while patients with heart failure may have values of 20 or lower.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 38.} Low cardiorespiratory fitness is linked to a markedly higher risk of early death, and the American Heart Association counts it as a clinical vital sign.^{2Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 199.}

In practice

• Aerobic training typically raises VO2 max by about 10% to 15%, with larger percentage gains in less-fit clients.^{1Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 38.} Untrained clients may improve by as much as 20% and elite athletes by 5% to 10%, with genetics partly setting the ceiling.^{3Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 142.}
• The gold standard is a graded test to exhaustion with expired gases measured; if oxygen uptake doesn’t plateau, the result is often called VO2 peak.^{4Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 201.}
• For untrained or sedentary clients, a submaximal test is safer and gives a solid estimate.^{5International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 187.} These tests tend to underpredict in highly trained clients, for whom the IPTA recommends maximal testing.^{5International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 187.}
• VO2 max alone doesn’t determine performance: two clients with the same value can sustain different outputs if one has a higher lactate threshold.^{3Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 142.}