VO2 max (also maximal oxygen consumption, maximal oxygen uptake, peak oxygen uptake or maximal aerobic capacity) is the maximum capacity of an individual's body to transport and use oxygen during incremental exercise, which reflects the physical fitness of the individual. The name is derived from V - volume, O2 - oxygen, max - maximum.
VO2 max is expressed either as an absolute rate in litres of oxygen per minute (L/min) or as a relative rate in millilitres of oxygen per kilogram of bodyweight per minute (mL/kg/min). The latter expression is often used to compare the performance of endurance sports athletes.
Measuring VO2 max
Accurately measuring VO2 max involves a physical effort sufficient in duration and intensity to fully tax the aerobic energy system. In general clinical and athletic testing, this usually involves a graded exercise test (either on a treadmill or on a cycle ergometer) in which exercise intensity is progressively increased while measuring ventilation and oxygen and carbon dioxide concentration of the inhaled and exhaled air. VO2 max is reached when oxygen consumption remains at steady state despite an increase in workload.
VO2 max is properly defined by the Fick equation:
- , when these values are obtained during an exertion at a maximal effort.
- where Q is the cardiac output of the heart, CaO2 is the arterial oxygen content, and CvO2 is the venous oxygen content.
Estimation of VO2 max
Tests measuring VO2 max can be dangerous in individuals who are not considered normal healthy subjects, as any problems with the respiratory and cardiovascular systems will be greatly exacerbated in clinically ill patients. Thus, many protocols for estimating VO2 max have been developed for those for whom a traditional VO2 max test would be too risky. These generally are similar to a VO2 max test, but do not reach the maximum of the respiratory and cardiovascular systems and are called sub-maximal tests.
Another estimate of VO2 max, based on maximum and resting heart rates, was created by a group of researchers from Denmark. It is given by:
This equation uses maximum heart rate (HRmax) and resting heart rate (HRrest) to estimate VO2 max in ml/min/kg.
Kenneth H. Cooper conducted a study for the United States Air Force in the late 1960s. One of the results of this was the Cooper test in which the distance covered running in 12 minutes is measured. Based on the measured distance, an estimate of VO2 max (in ml/min/kg) is:
where d12 is distance (in metres) covered in 12 minutes. There are several other reliable tests and VO2 max calculators to estimate VO2 max, most notably the multi-stage fitness test (or bleep test), based on the research paper by Leger and Lambert, "A Maximal Multi-Stage 20m Shuttle Run Test to predict VO2 Max".
VO2 max levels
“Maximal oxygen uptake (VO2 max) is widely accepted as the single best measure of cardiovascular fitness and maximal aerobic power. Absolute values of VO2 max are typically 40-60% higher in men than in women.”
The average untrained healthy male will have a VO2 max of approximately 35-40 ml/kg/min. The average untrained healthy female will score a VO2 max of approximately 27-31 ml/kg/min. These scores can improve with training and decrease with age, though the degree of trainability also varies very widely: conditioning may double VO2 max in some individuals, and will marginally improve it in others.
In sports where endurance is an important component in performance, such as cycling, rowing, cross-country skiing, swimming and running, world class athletes typically have high VO2 maxima. Elite male runners can consume up to 85 ml/kg/min, and female elite runners can consume about 77 ml/kg/min. Five time Tour de France winner Miguel Indurain is reported to have had a VO2 max of 88.0 at his peak, while cross-country skier Bjørn Dæhlie measured at 96 ml/kg/min. Dæhlie's result was achieved out of season, and physiologist Erlend Hem who was responsible for the testing stated that he would not discount the possibility of the skier passing 100 ml/kg/min at his absolute peak. Norwegian cyclist Oskar Svendsen is thought to have recorded the highest VO2 max of 97.5 ml/kg/min, a "sensational" value in itself, made more remarkable by his young age (18 years old at the time). To put this into perspective, thoroughbred horses have a VO2 max of around 180 ml/kg/min. Siberian dogs running in the Iditarod Trail Sled Dog Race have VO2 values as high as 240 ml/kg/min.
The highest values in absolute terms are often found in rowers, as their much greater bulk makes up for a slightly lower VO2 max per kg. Elite oarsmen measured in 1984 had VO2 max values of 6.1 ±0.6 l/min and oarswomen 4.1 ±0.4 l/min. Rowers are interested in both absolute values of VO2 max and in lung capacity, and the fact that they are measured in similar units means that the two are often confused. British rower Sir Matthew Pinsent is variously reported to have had a VO2 of 7.5l/min or 8.5l/min, although the latter may represent confusion with his lung capacity of 8.5 litres. New Zealand sculler Rob Waddell has one of the highest absolute VO2 max levels ever tested.
Factors affecting VO2 max
The factors affecting VO2 are often divided into supply and demand factors. Supply is the transport of oxygen from the lungs to the mitochondria (including lung diffusion, stroke volume, blood volume, and capillary density of the skeletal muscle) while demand is the rate at which the mitochondria can reduce oxygen in the process of oxidative phosphorylation. Of these, the supply factor is often considered to be the limiting one. However, it has also been argued that while trained subjects probably are supply limited, untrained subjects can indeed have a demand limitation.
Tim Noakes, a professor of exercise and sports science at the University of Cape Town, describes a number of variables that may affect VO2 max: age, gender, fitness and training, changes in altitude, and action of the ventilatory muscles. Noakes also asserts that VO2 max is a relatively poor predictor of performance in runners due to variations in running economy and fatigue resistance during prolonged exercise.
Cardiac output, pulmonary diffusion capacity, oxygen carrying capacity, and other peripheral limitations like muscle diffusion capacity, mitochondrial enzymes, and capillary density are all examples of VO2 max determinants. The body works as a system. If one of these factor is sub-par, then the whole system loses its normal capacity to function properly.
In theory, the drug Erythropoietin (EPO) can boost VO2 by a significant amount. This makes it attractive to athletes in endurance sports like professional cycling. By 1998 it had become widespread in cycling and led to the Festina affair as well as being mentioned ubiquitously in the USADA 2012 report on the US Postal team. Greg LeMond has suggested establishing a baseline for riders' VO2 (and other attributes) to detect abnormal performance increases.
- Anaerobic exercise
- Arteriovenous oxygen difference
- Cardiorespiratory fitness
- Training effect
- "Arteriovenous oxygen difference". Sports Medicine, Sports Science and Kinesiology. Net Industries and its Licensors. 2011. Retrieved 30 April 2011.
- Uth, Niels; Henrik Sørensen, Kristian Overgaard, Preben K. Pedersen (January 2004). "Estimation of VO2max from the ratio between HRmax and HRrest--the Heart Rate Ratio Method". Eur J Appl Physiol. 2004 Jan;91(1):111-5. Retrieved 2009-11-03.
- Thomas E. Hyde and Marianne S. Gengenbach, Conservative Management of Sports Injuries (2nd ed; Sudbury, Mass.: Jones & Bartlett, 2007), 845.
- Heywood, V (1998). "Advance Fitness Assessment & Exercise Prescription, 3rd Ed". p. 48.
- Guyton, A. & Hall, J.E. (2011). "Textbook of Medical Physiology, 12th Ed.". pp. 1035–1036.
- Bouchard, Claude; Ping An, Treva Rice, James S. Skinner, Jack H. Wilmore, Jacques Gagnon, Louis Perusse, Arthus S. Leon, D. C. Rao (September 1, 1999). "Familial aggregation of VO(2max) response to exercise training: results from the HERITAGE Family Study". Journal of Applied Physiology 87 (3): 1003–1008. PMID 10484570. Retrieved 2007-07-17.
- Kolata, Gina (February 12, 2002). "Why Some People Won't Be Fit Despite Exercise". The New York Times. Retrieved 2007-07-17.
- Noakes, Tim. 2001. The Lore of Running. (3rd edition) Oxford University Press ISBN 978-0-88011-438-7
- Ski-VM 1997
- If all goes to plan, big future predicted for junior world champion Oskar Svendsen
- Cornell Science News
- Hagerman, FC (1984 Jul-Aug). "Applied physiology of rowing". Sports Med. 1(4): 303–26.
- Bailey, James. "Intensity (3 of 6)". Q-power indoor rowing team.
- "What happens in a VO2 max test?". BBC Sport. 2009. - see an example here, which suggests that although British rower Pete Reed has recorded a lung capacity of 11.68 litres,(Hounslow Chronicle) Pinsent still regards his VO2 record as safe. A large lung capacity appears to be a particular advantage for rowing as it allows a rower to row more strokes at one breath per stroke.
- Gough, Martin (17 June 2009). "Monsters wanted". BBC.
- Bassett D.R Jr. & Howley E.T. (2000) Limiting factors for maximum oxygen uptake and determinants of endurance performance. Med Sci Sports Exerc. 32(1):70-84.
- Bassett D.R Jr. & Howley E.T. (1997) Maximal oxygen uptake: "classical" versus "contemporary" viewpoints. Med Sci Sports Exerc 29(5) 591-603
- Wagner, P.D. (2000) New ideas on limitations to VO2max. Exercise and Sport Sciences Reviews. 28(1):10-4.
- Does recombinant human Epo increase exercise capacity by means other than augmenting oxygen transport? C. Lundby, P. Robach, R. Boushel, J. J. Thomsen, P. Rasmussen, M. Koskolou, J. A. L. Calbet. June 5, 2008, Journal of Applied Physiology doi: 10.1152/japplphysiol.90484.2008
- EPO EPIDEMIC IN CYCLING: Some Empirical Notes on the ‗Epo Epidemic‘ in Professional Cycling, Hein F.M. Lodewijkx and Bram Brouwer, Department of Psychology, Open University, Heerlen, the Netherlands, 2011, 82 (4), 740-754 DOI: http://dx.doi.org/10.5641/027013611X13275192112069
- USADA U.S. Postal Service Pro Cycling Team Investigation, Oct 2012, retr 2012 10 20 from usada.org
- Greg LeMond’s suggestions for a credible future for cycling Conal Andrews, July 28, 2010, Velo Nation, retr 2012 10 20