VO2 max

"VO2" redirects here. For the chemical compound, see Vanadium(IV) oxide.

VO₂ max (also maximal oxygen consumption, maximal oxygen uptake, peak oxygen uptake or 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.

Fick equation

Main article: Fick principle

VO₂ max is properly defined by the Fick equation:

$\mathrm{VO_2\; max} = Q(\mathrm{CaO_2} - \mathrm{CvO_2})$, 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.

(CaO₂ – CvO₂) is also known as the arteriovenous oxygen difference.^[1]

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.

Uth—Sørensen—Overgaard—Pedersen estimation

Another estimate of VO₂ max, based on maximum and resting heart rates, was created by a group of researchers from Denmark.^[2] It is given by:

$\mathrm{VO_2\; max} = {15{ \mbox{HR}_{max} \over \mbox{HR}_{rest} }}$

This equation uses maximum heart rate (HR_max) and resting heart rate (HR_rest) to estimate VO₂ max in ml/min/kg.

Cooper test

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:

$\mathrm{VO_2\; max} = {d_{12} - 505 \over 45}$

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 (VO₂max) is widely accepted as the single best measure of cardiovascular fitness and maximal aerobic power. Absolute values of VO₂max are typically 40-60% higher in men than in women.”^[3]

The average young untrained male will have a VO₂ max of approximately 3.5 litres/minute and 45 ml/kg/min.^[4] The average young untrained female will score a VO₂ max of approximately 2.0 litres/minute and 38 ml/kg/min.^[4] These scores can improve with training and decrease with age, though the degree of trainability also varies very widely: conditioning may double VO₂max in some individuals, and will never improve at all in others.^[5][6]

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 maximums. Elite male runners can generate up to 85 ml/kg/min, and female elite runners can generate about 77 ml/kg/min ^[7]. Five time Tour de France winner Miguel Indurain is reported to have had a VO₂ max of 88.0 at his peak,^[8] while cross-country skier Bjørn Dæhlie measured at 96 ml/kg/min.^[9] 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. By comparison a competitive club athlete might achieve a VO₂ max of around 70 ml/kg/min.^[4] World class rowers are physically very large endurance athletes and typically do not score as high on a per weight basis, but often score exceptionally high in absolute terms. Male rowers typically score VO₂ maximums over 6 litres/minute, and some exceptional individuals have exceeded 8 l/min.

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.^[10]

Factors affecting VO₂ max

The factors affecting VO₂ are often divided into supply and demand factors.^[11] 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.^[11] Of these, the supply factor is often considered to be the limiting one.^[11][12] However, it has also been argued that while trained subjects probably are supply limited, untrained subjects can indeed have a demand limitation.^[13]

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.^[7] 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.^[7]

Needless to say, 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.^[13]

See also

• Anaerobic exercise
• Arteriovenous oxygen difference
• Cardiorespiratory fitness
• Respirometry
• Training effect
• VDOT
• vVO₂max

References

1. ^ "Arteriovenous oxygen difference". Sports Medicine, Sports Science and Kinesiology. Net Industries and its Licensors. 2011. http://sports.jrank.org/pages/5973/arteriovenous-oxygen-difference.html. Retrieved 30 April 2011. 
2. ^ 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. http://www.ncbi.nlm.nih.gov/pubmed/14624296. Retrieved 2009-11-03. 
3. ^ Thomas E. Hyde and Marianne S. Gengenbach, Conservative Management of Sports Injuries (2nd ed; Sudbury, Mass.: Jones & Bartlett, 2007), 845.
4. ^ ^{a b c} Geddes, Linda (2007-07-28). "Superhuman". New Scientist. pp. 35–41. 
5. ^ 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. http://jap.physiology.org/cgi/content/abstract/87/3/1003?ijkey=189eebcbc5a461258da582b4aef41ebcf7bec51f&keytype2=tf_ipsecsha. Retrieved 2007-07-17. 
6. ^ Kolata, Gina (February 12, 2002). "Why Some People Won't Be Fit Despite Exercise". The New York Times. http://query.nytimes.com/gst/fullpage.html?res=9406EEDE113CF931A25751C0A9649C8B63&sec=health. Retrieved 2007-07-17. 
7. ^ ^{a b c} Noakes, Tim. 2001. The Lore of Running. (3rd edition) Oxford University Press ISBN 978-0880114387
8. ^ http://www.runningforfitness.org/faq/vo2.php
9. ^ Ski-VM 1997
10. ^ Cornell Science News
11. ^ ^{a b c} 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.
12. ^ Bassett D.R Jr. & Howley E.T. (1997) Maximal oxygen uptake: "classical" versus "contemporary" viewpoints. Med Sci Sports Exerc 29(5) 591-603
13. ^ ^{a b} Wagner, P.D. (2000) New ideas on limitations to VO2max. Exercise and Sport Sciences Reviews. 28(1):10-4.

External links

• VO₂ max Calculator - the Rockport Walking Test
• All About VO2max - Horses
• So What Exactly is VO2?