View source for VO2 max

{{Distinguish|Vanadium(IV) oxide}}
{{See also|Cardiorespiratory fitness}}
{{Short description|Maximum rate of oxygen consumption as measured during incremental exercise}}
{{Use dmy dates|date=January 2023}}
{{DISPLAYTITLE:VO<sub>2</sub> max}}
'''V̇O<sub>2</sub> max''' (also '''maximal oxygen consumption''', '''maximal oxygen uptake''' or '''maximal aerobic capacity''') is the maximum rate of [[respiration (physiology)|oxygen consumption]] attainable during physical exertion.<ref name=Clemente_et_al_2009>{{cite journal |author1=Clemente C. J. |author2=Withers P. C. |author3=Thompson G. G. | year = 2009 | title = Metabolic rate and endurance capacity in Australian varanid lizards (Squamata; Varanidae; Varanus) | journal = Biological Journal of the Linnean Society | volume = 97 | issue = 3| pages = 664–676 | doi=10.1111/j.1095-8312.2009.01207.x| doi-access = free }}</ref><ref name=Dlugosz_et_al_2013>{{cite journal | year = 2013 | title = Phylogenetic analysis of mammalian maximal oxygen consumption during exercise | url = http://jeb.biologists.org/content/jexbio/216/24/4712.full.pdf| journal = Journal of Experimental Biology | volume = 216 | issue = 24| pages = 4712–4721 | doi=10.1242/jeb.088914 | pmid=24031059| s2cid = 15686903 | doi-access = free | last1 = Dlugosz | first1 = Elizabeth M. | last2 = Chappell | first2 = Mark A. | last3 = Meek | first3 = Thomas H. | last4 = Szafrańska | first4 = Paulina | last5 = Zub | first5 = Karol | last6 = Konarzewski | first6 = Marek | last7 = Jones | first7 = James H. | last8 = Bicudo | first8 = Eduardo | last9 = Nespolo | first9 = Roberto F. | last10 = Careau | first10 = Vincent | last11 = Garland | first11 = Theodore }}</ref> The name is derived from three abbreviations: "V̇" for [[volume]] (the dot over the V indicates "per unit of time" in [[Newton's notation]]), "O<sub>2</sub>" for [[oxygen]], and "max" for maximum and usually normalized per kilogram of body mass. A similar measure is '''V̇O<sub>2</sub> peak''' ('''peak oxygen consumption'''), which is the measurable value from a session of physical exercise, be it incremental or otherwise. It could match or underestimate the actual V̇O<sub>2</sub> max. Confusion between the values in older and popular fitness literature is common.<ref name="pmid23935584">{{cite journal |last1=Smirmaul |first1=BP |last2=Bertucci |first2=DR |last3=Teixeira |first3=IP |title=Is the VO2max that we measure really maximal? |journal=Frontiers in Physiology |year=2013 |volume=4 |pages=203 |doi=10.3389/fphys.2013.00203 |pmid=23935584 |pmc=3733001|doi-access=free }}</ref> The capacity of the lung to exchange oxygen and carbon dioxide is constrained by the rate of [[blood#Oxygen transport| blood oxygen transport]] to active tissue. 

The measurement of V̇O<sub>2</sub> max in the laboratory provides a quantitative value of endurance fitness for comparison of individual training effects and between people in [[endurance training]]. Maximal oxygen consumption reflects [[cardiorespiratory fitness]] and [[endurance]] capacity in exercise performance. Elite athletes, such as [[long-distance running|competitive distance runners]], [[Road bicycle racing|racing cyclists]] or [[cross-country skiing (sport)|Olympic cross-country skiers]], can achieve V̇O<sub>2</sub> max values exceeding 90&nbsp;mL/(kg·min), while some endurance animals, such as [[Alaskan husky|Alaskan huskies]], have V̇O<sub>2</sub> max values exceeding 200&nbsp;mL/(kg·min).

In [[physical training]], especially in its academic literature, V̇O<sub>2</sub> max is often used as a reference level to quantify exertion levels, such as 65% V̇O<sub>2</sub> max as a threshold for sustainable exercise, which is generally regarded as more rigorous than [[heart rate#Maximum heart rate|heart rate]], but is more elaborate to measure. 

==Normalization per body mass==
V̇O<sub>2</sub> max is expressed either as an absolute rate in (for example) litres of oxygen per minute (L/min) or as a relative rate in (for example) millilitres of oxygen per kilogram of the body [[mass]] per minute (e.g., mL/(kg·min)). The latter expression is often used to compare the performance of endurance sports athletes. However, V̇O<sub>2</sub> max generally does not vary linearly with body mass, either among individuals within a species or among species, so comparisons of the performance capacities of individuals or species that differ in body size must be done with appropriate statistical procedures, such as [[analysis of covariance]].<ref name=Dlugosz_et_al_2013 />

==Measurement and calculation==
===Measurement===
[[File:Ergospirometry laboratory.jpg|thumb|VO<sub>2</sub> max measurement using instruments on a metabolic cart during a graded treadmill exercise test]]

[[File:Gas_exchange_during_max_test.jpg|thumb|Gas exchange of VO<sub>2</sub> and VCO<sub>2</sub> during max test. Begin for 3 minutes at 60 watts and add 35 watts every 3 mins until exhaustion.]]

Accurately measuring V̇O<sub>2</sub> 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 in which exercise intensity is progressively increased while measuring: 
* [[Ventilation (physiology)|ventilation]] and 
* oxygen and carbon dioxide concentration of the inhaled and exhaled air.

V̇O<sub>2</sub> max is measured during a [[cardiopulmonary exercise test]] (CPX test). The test is done on a [[treadmill]] or [[cycle ergometer]]. In untrained subjects, V̇O<sub>2</sub> max is 10% to 20% lower when using a cycle ergometer compared with a treadmill.<ref name=Kaminsky2017>{{Cite journal |last1=Kaminsky |first1=Leonard A. |last2=Imboden |first2=Mary T. |last3=Arena |first3=Ross |last4=Myers |first4=Jonathan |date=2017 |title=Reference Standards for Cardiorespiratory Fitness Measured With Cardiopulmonary Exercise Testing Using Cycle Ergometry: Data From the Fitness Registry and the Importance of Exercise National Database (FRIEND) Registry |url=https://linkinghub.elsevier.com/retrieve/pii/S0025619616306243 |journal=Mayo Clinic Proceedings |language=en |volume=92 |issue=2 |pages=228–233 |doi=10.1016/j.mayocp.2016.10.003|pmid=27938891 |s2cid=3465353 }}</ref> However, trained cyclists' results on the cycle ergometer are equal to or even higher than those obtained on the treadmill.<ref>{{Cite journal |last1=Basset |first1=Fabien A. |last2=Boulay |first2=Marcel R. |date=2000-01-01 |title=Specificity of treadmill and cycle ergometer tests in triathletes, runners and cyclists |url=http://link.springer.com/10.1007/s004210050033 |journal=European Journal of Applied Physiology |volume=81 |issue=3 |pages=214–221 |doi=10.1007/s004210050033 |pmid=10638380 |s2cid=24902705 |issn=1439-6319}}</ref><ref>{{Cite journal |last1=Bouckaert |first1=J. |last2=Vrijens |first2=J. |last3=Pannier |first3=J. L. |date=1990 |title=Effect of specific test procedures on plasma lactate concentration and peak oxygen uptake in endurance athletes |url=https://pubmed.ncbi.nlm.nih.gov/2366529/ |journal=The Journal of Sports Medicine and Physical Fitness |volume=30 |issue=1 |pages=13–18 |issn=0022-4707 |pmid=2366529}}</ref><ref>{{Cite journal |last1=Costa |first1=M. M. |last2=Russo |first2=A. K. |last3=Pićarro |first3=I. C. |last4=Barros Neto |first4=T. L. |last5=Silva |first5=A. C. |last6=Tarasantchi |first6=J. |date=1989 |title=Oxygen consumption and ventilation during constant-load exercise in runners and cyclists |url=https://pubmed.ncbi.nlm.nih.gov/2770266/ |journal=The Journal of Sports Medicine and Physical Fitness |volume=29 |issue=1 |pages=36–44 |issn=0022-4707 |pmid=2770266}}</ref>

The classic V̇O<sub>2</sub> max, in the sense of Hill and Lupton (1923), is reached when oxygen consumption remains at a steady state ("plateau") despite an increase in workload. The occurrence of a plateau is not guaranteed and may vary by person and sampling interval, leading to modified protocols with varied results.<ref name="pmid23935584"/>

===Calculation: the Fick equation===
{{Main|Fick principle}}
V̇O<sub>2</sub> may also be calculated by the [[Fick principle|Fick equation]]:
<math chem>\ce{\dot VO2} = Q \times\ (C_a\ce{O2} - C_v\ce{O2})</math>, when these values are obtained during exertion at a maximal effort. Here ''Q'' is the [[cardiac output]] of the heart, ''C<sub>a</sub>''O<sub>2</sub> is the arterial oxygen content, and ''C<sub>v</sub>''O<sub>2</sub> is the venous oxygen content. (''C<sub>a</sub>''O<sub>2</sub> – ''C<sub>v</sub>''O<sub>2</sub>) is also known as the [[arteriovenous oxygen difference]].

The Fick equation may be used to measure V̇O<sub>2</sub> in critically ill patients, but its usefulness is low even in non-exerted cases.<ref>{{cite journal |last1=Thrush |first1=DN |title=Spirometric versus Fick-derived oxygen consumption: which method is better? |journal=Critical Care Medicine |date=January 1996 |volume=24 |issue=1 |pages=91–5 |doi=10.1097/00003246-199601000-00016 |pmid=8565545}}</ref> Using a breath-based VO<sub>2</sub> to estimate cardiac output, on the other hand, seems to be reliable enough.<ref>{{cite journal |last1=Fanari |first1=Z |last2=Grove |first2=M |last3=Rajamanickam |first3=A |last4=Hammami |first4=S |last5=Walls |first5=C |last6=Kolm |first6=P |last7=Saltzberg |first7=M |last8=Weintraub |first8=WS |last9=Doorey |first9=AJ |title=Cardiac output determination using a widely available direct continuous oxygen consumption measuring device: a practical way to get back to the gold standard. |journal=Cardiovascular Revascularization Medicine: Including Molecular Interventions |date=June 2016 |volume=17 |issue=4 |pages=256–61 |doi=10.1016/j.carrev.2016.02.013 |pmid=26976237 |pmc=4912455}}</ref>

==Estimation using submaximal exercise testing==
The necessity for a subject to exert maximum effort in order to accurately measure V̇O<sub>2</sub> max can be dangerous in those with compromised respiratory or cardiovascular systems; thus, [[Submaximal performance testing|sub-maximal tests]] for ''estimating'' V̇O<sub>2</sub> max have been developed.

===The heart rate ratio method===
An estimate of V̇O<sub>2</sub> max is based on maximum and resting heart rates. In the Uth ''et al.'' (2004) formulation, it is given by:<ref name="uth">{{cite journal|title=Estimation of VO2max from the ratio between HRmax and HRrest--the Heart Rate Ratio Method|last=Uth|first=Niels|author2=Henrik Sørensen |author3=Kristian Overgaard |author4=Preben K. Pedersen |date=January 2004|journal=Eur J Appl Physiol |volume=91|pages=111–5 |pmid=14624296 |doi=10.1007/s00421-003-0988-y |issue=1|s2cid=23971067|url=https://pure.au.dk/ws/files/14557663/UTH2004.pdf}}</ref>
:<math chem>\ce{\dot VO2}\max \approx \frac{\text{HR}_\max}{\text{HR}_\text{rest}} \times 15.3\text{ mL}/(\text{kg}\cdot\text{minute})</math>

This equation uses the ratio of maximum heart rate (HR<sub>max</sub>) to resting heart rate (HR<sub>rest</sub>) to predict V̇O<sub>2</sub> max. The researchers cautioned that the conversion rule was based on measurements on well-trained men aged 21 to 51 only, and may not be reliable when applied to other sub-groups. They also advised that the formula is most reliable when based on actual measurement of maximum heart rate, rather than an age-related estimate.

The Uth constant factor of 15.3 is given for well-trained men.<ref name="uth"/> Later studies have revised the constant factor for different populations. According to Voutilainen ''et al.'' 2020, the constant factor should be 14 in around 40-year-old normal weight never-smoking men with no cardiovascular diseases, bronchial asthma, or cancer.<ref name="voutilainen">{{cite journal|title=Estimating Maximal Oxygen Uptake from the Ratio of Heart Rate at Maximal Exercise to Heart Rate at Rest in Middle-Aged Men|last=Voutilainen|first=Ari |author2=Mounir Ould Setti |author3=Tomi-Pekka Tuomainen |date=July 2020|journal=World J Mens Health |volume=38|issue=4|pages=666–672 |doi=10.5534/wjmh.200055|pmc=8443998 |issn=2287-4208 |pmid=32777866|url=https://wjmh.org/Synapse/Data/PDFData/2074WJMH/wjmh-38-e39.pdf|doi-access=free}}</ref>
Every 10 years of age reduces the coefficient by one, as well as does the change in body weight from normal weight to obese or the change from never-smoker to current smoker. Consequently, V̇O<sub>2</sub> max of 60-year-old obese current smoker men should be estimated by multiplying the HR<sub>max</sub> to HR<sub>rest</sub> ratio by 10.

===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.<ref>{{cite journal |last1=Cooper |first1=Kenneth H. |title=A Means of Assessing Maximal Oxygen Intake: Correlation Between Field and Treadmill Testing |journal=JAMA |date=15 January 1968 |volume=203 |issue=3 |pages=203 |doi=10.1001/jama.1968.03140030033008 |url=https://doi.org/10.1001/jama.1968.03140030033008 |language=en |issn=0098-7484}}</ref> Based on the measured distance, an estimate of V̇O<sub>2</sub> max [in mL/(kg·min)] can be calculated by inverting the linear regression equation, giving us:

:<math chem>\ce{\dot VO2}\max \approx {d_{12} - 504.9 \over 44.73}</math>

where ''d''<sub>12</sub> is the distance (in metres) covered in 12 minutes.

An alternative equation is:

:<math chem>\ce{\dot VO2}\max \approx {(35.97 * d'_{12}) - 11.29}</math>

where ''d''&prime;<sub>12</sub> is distance (in miles) covered in 12 minutes.

=== Multi-stage fitness test ===
There are several other reliable tests and V̇O<sub>2</sub> max calculators to estimate V̇O<sub>2</sub> max, most notably the [[multi-stage fitness test]] (or ''beep'' test).<ref>[Leger, Luc A., and J_ Lambert. "A maximal multistage 20-m shuttle run test to predict\ dot VO2 max." European journal of applied physiology and occupational physiology 49.1 (1982): 1-12.]</ref>

=== Rockport fitness walking test ===
Estimation of V̇O<sub>2</sub> max from a timed one-mile track walk (as fast as possible) in decimal minutes ({{mvar|t}}, e.g.: 20:35 would be specified as 20.58), sex, age in years, body weight in pounds ({{math|BW}}, lbs), and 60-second heart rate in beats-per-minute ({{math|HR}}, bpm) at the end of the mile.<ref>{{cite journal |vauthors=Kilne G, etal | year = 1987 | title = Estimation of VO2 max from a one mile track walk, sex, age and body weight | journal = Med. Sci. Sports Exerc. | volume = 19 | issue = 3| pages = 253–259 | pmid = 3600239 }}</ref> The constant {{mvar|x}} is 6.3150 for males, 0 for females.

:<math chem>\ce{\dot VO2}\max \approx 132.853 -0.0769\cdot\text{BW} -0.3877\cdot\text{age} -3.2649t -0.1565\cdot\text{HR} +x</math>

[[Correlation coefficient]] {{mvar|r}} for the generalized formula is 0.88.

==Reference values==
Men have a V̇O<sub>2</sub> max that is 26% higher (6.6 mL/(kg·min)) than women for treadmill and 37.9% higher (7.6 mL/(kg·min)) than women for cycle ergometer on average.<ref name=Kaminsky2022/> V̇O<sub>2</sub> max is on average 22% higher (4.5 mL/(kg·min)) when measured using a treadmill compared with a cycle ergometer.<ref name=Kaminsky2022/>

{| class="wikitable"
|+V̇O<sub>2</sub> percentiles by age group for treadmill and cycle ergometer cardiopulmonary exercise, in mL/(kg·min)<ref name=Kaminsky2022>{{Cite journal |last1=Kaminsky |first1=Leonard A. |last2=Arena |first2=Ross |last3=Myers |first3=Jonathan |last4=Peterman |first4=James E. |last5=Bonikowske |first5=Amanda R. |last6=Harber |first6=Matthew P. |last7=Medina Inojosa |first7=Jose R. |last8=Lavie |first8=Carl J. |last9=Squires |first9=Ray W. |date=2022 |title=Updated Reference Standards for Cardiorespiratory Fitness Measured with Cardiopulmonary Exercise Testing |journal=Mayo Clinic Proceedings |language=en |volume=97 |issue=2 |pages=285–293 |doi=10.1016/j.mayocp.2021.08.020|pmid=34809986 |doi-access=free }}</ref>
|-
! rowspan="3" | Percentile
! colspan="14" | Age group, in years
|-
! colspan="7" | Men
! colspan="7" | Women
|-
! 20–29 !! 30–39 !! 40–49 !! 50–59 !! 60–69 !! 70–79 !! 80–89 !! 20–29 !! 30–39 !! 40–49 !! 50–59 !! 60–69 !! 70–79 !! 80–89
|-
! colspan="15" | Treadmill
|-
! 90
| 58.6 || 55.5 || 50.8 || 43.4 || 37.1 || 29.4 || 22.8 || 49.0 || 42.1 || 37.8 || 32.4 || 27.3 || 22.8 || 20.8
|-
! 80
| 54.5 || 50.0 || 45.2 || 38.3 || 32.0 || 25.9 || 21.4 || 44.8 || 37.0 || 33.0 || 28.4 || 24.3 || 20.8 || 18.4
|-
! 70
| 51.9 || 46.4 || 40.9 || 34.3 || 28.7 || 23.8 || 20.0 || 41.8 || 33.6 || 30.0 || 26.3 || 22.4 || 19.6 || 17.3
|-
! 60
| 49.0 || 43.4 || 37.9 || 31.8 || 26.5 || 22.2 || 18.4 || 39.0 || 31.0 || 27.7 || 24.6 || 20.9 || 18.3 || 16.0
|-
! 50
| 46.5 || 39.7 || 35.3 || 29.2 || 24.6 || 20.6 || 17.6 || 36.6 || 28.3 || 25.7 || 22.9 || 19.6 || 17.2 || 15.4
|-
! 40
| 43.6 || 37.0 || 32.4 || 26.9 || 22.8 || 19.1 || 16.6 || 34.0 || 26.4 || 23.9 || 21.5 || 18.3 || 16.2 || 14.7
|-
! 30
| 40.0 || 33.5 || 29.7 || 24.5 || 20.7 || 17.3 || 16.1 || 30.8 || 24.2 || 21.8 || 20.1 || 17.0 || 15.2 || 13.7
|-
! 20
| 35.2 || 29.8 || 26.7 || 22.2 || 18.5 || 15.9 || 14.8 || 27.2 || 21.9 || 19.7 || 18.5 || 15.4 || 14.0 || 12.6
|-
! 10
| 28.6 || 24.9 || 22.1 || 18.6 || 15.8 || 13.6 || 12.9 || 22.5 || 18.6 || 17.2 || 16.5 || 13.4 || 12.3 || 11.4
|-
! colspan="15" | Cycle ergometer
|-
! 90
| 62.2 || 50.5 || 41.9 || 37.1 || 31.4 || 26.2 || 18.7 || 46.0 || 32.0 || 27.3 || 22.4 || 20.3 || 18.0 || 18.1
|-
! 80
| 57.0 || 39.0 || 35.1 || 31.6 || 27.0 || 22.6 || 17.3 || 40.9 || 27.0 || 23.5 || 20.4 || 18.5 || 16.8 || 14.3
|-
! 70
| 52.8 || 35.5 || 31.4 || 28.4 || 24.5 || 20.6 || 16.2 || 37.5 || 24.5 || 21.8 || 18.9 || 17.4 || 15.9 || 12.9
|-
! 60
| 48.3 || 31.6 || 29.0 || 26.3 || 23.3 || 19.4 || 14.6 || 34.3 || 22.9 || 20.3 || 17.8 || 16.4 || 15.0 || 11.3
|-
! 50
| 44.0 || 30.2 || 27.4 || 24.5 || 21.7 || 18.3 || 13.2 || 31.6 || 21.6 || 18.8 || 16.9 || 15.7 || 14.5 || 10.9
|-
! 40
| 40.8 || 27.9 || 25.4 || 23.1 || 20.7 || 17.1 || 12.2 || 28.9 || 19.9 || 17.9 || 16.1 || 15.0 || 13.6 || 10.1
|-
! 30
| 37.4 || 25.7 || 23.8 || 22.0 || 19.1 || 16.0 || 11.1 || 25.6 || 18.6 || 16.6 || 15.2 || 14.2 || 12.9 || 9.4
|-
! 20
| 34.5 || 22.6 || 21.9 || 20.2 || 17.5 || 14.7 || 9.7 || 21.9 || 17.0 || 15.4 || 14.3 || 13.4 || 12.0 || 8.7
|-
! 10
| 28.8 || 19.1 || 19.8 || 17.2 || 14.7 || 11.0 || 8.4 || 18.8 || 15.0 || 13.7 || 13.0 || 12.2 || 10.7 || 7.8
|}

==Effect of training==
===Non-athletes===
The average untrained healthy male has a V̇O<sub>2</sub> max of approximately 35–40 mL/(kg·min).<ref name="Heyward_1998">{{cite news
|last = Heyward
| first = V
| title = Advance Fitness Assessment & Exercise Prescription, 3rd Ed
| page = 48
| year = 1998
}}</ref><ref name="Guyton_2011">{{cite news
|author1=Guyton, A. |author2=Hall, J.E.
| title = Textbook of Medical Physiology, 12th Ed.
| pages = 1035–1036
| year = 2011
}}</ref> The average untrained healthy female has a V̇O<sub>2</sub> max of approximately 27–31 mL/(kg·min).<ref name="Heyward_1998"/> These scores can improve with training and decrease with age, though the degree of trainability also varies widely.<ref>{{cite journal |last1=Williams |first1=Camilla |last2=Williams |first2=Mark |last3=Coombes |first3=Jeff |title=Genes to predict VO2max trainability: a systematic review |journal=BMC Genomics |date=14 November 2017 |volume=18 |issue=Suppl 8 |page=831 |doi=10.1186/s12864-017-4192-6 |pmid=29143670 |pmc=5688475 |doi-access=free }}</ref>

===Athletes===
In sports where endurance is an important component in performance, such as [[road bicycle racing|road cycling]], [[rowing (sport)|rowing]], [[cross-country skiing (sport)|cross-country skiing]], swimming, and [[long-distance running]], world-class athletes typically have high V̇O<sub>2</sub> max values. Elite male runners can consume up to 85 mL/(kg·min), and female elite runners can consume about 77&nbsp;mL/(kg·min).<ref name="Noakes3ed">Noakes, Tim (2001). ''The Lore of Running''. (3rd edition) [[Oxford University Press]] {{ISBN|978-0-88011-438-7}}</ref>

Norwegian cyclist [[Oskar Svendsen]] holds the record for the highest V̇O<sub>2</sub> ever tested with 97.5 mL/(kg·min).<ref>{{Cite journal |last=Rønnestad |first=Bent R. |last2=Hansen |first2=Joar |last3=Stensløkken |first3=Lars |last4=Joyner |first4=Michael J. |last5=Lundby |first5=Carsten |date=2019-08-01 |title=Case Studies in Physiology: Temporal changes in determinants of aerobic performance in individual going from alpine skier to world junior champion time trial cyclist |url=https://www.physiology.org/doi/10.1152/japplphysiol.00798.2018 |journal=Journal of Applied Physiology |language=en |volume=127 |issue=2 |pages=306–311 |doi=10.1152/japplphysiol.00798.2018 |issn=8750-7587}}</ref><ref>{{cite web | url=http://www.topendsports.com/testing/records/vo2max.htm | title=VO2max records | work=Top End Sports | accessdate=27 July 2024}}</ref>

===Animals===
V̇O<sub>2</sub> max has been measured in other animal species. During loaded swimming, mice had a V̇O<sub>2</sub> max of around 140 mL/(kg·min).<ref>{{cite journal|doi=10.3181/00379727-140-36431|pmid=5033099|title=Maximal aerobic metabolism of mice during swimming|journal=Experimental Biology and Medicine|volume=140|issue=1|pages=230–233|year=1972|last1=Glaser|first1=R. M.|last2=Gross|first2=P. M.|last3=Weiss|first3=H. S.|s2cid=378983}}</ref> [[Thoroughbred horse]]s had a V̇O<sub>2</sub> max of around 193 mL/(kg·min) after 18 weeks of high-intensity training.<ref>{{cite journal|pmid=21148623|year=2011|last1=Kitaoka|first1=Y.|title=Effect of training and detraining on monocarboxylate transporter (MCT) 1 and MCT4 in Thoroughbred horses|journal=Experimental Physiology|volume=96|issue=3|pages=348–55|last2=Masuda|first2=H.|last3=Mukai|first3=K.|last4=Hiraga|first4=A.|last5=Takemasa|first5=T.|last6=Hatta|first6=H.|doi=10.1113/expphysiol.2010.055483|s2cid=28298003|doi-access=}}</ref> [[Alaskan husky|Alaskan huskies]] running in the [[Iditarod Trail Sled Dog Race]] had V̇O<sub>2</sub> max values as high as 240&nbsp;mL/(kg·min).<ref>{{cite web|url=http://www.news.cornell.edu/releases/Dec96/winterize.hrs.html|title=Winterize Rover for cold-weather fitness, Cornell veterinarian advises|author=Roger Segelke|work=Cornell University Chronicle|date=9 December 1996|access-date=7 December 2018 }}</ref> Estimated V̇O<sub>2</sub> max for [[pronghorn antelope]]s was as high as 300&nbsp;mL/(kg·min).<ref>{{cite journal|pmid=1944533|year=1991|last1=Lindstedt|first1=S. L.|title=Running energetics in the pronghorn antelope|journal=Nature|volume=353|issue=6346|pages=748–50|last2=Hokanson|first2=J. F.|last3=Wells|first3=D. J.|last4=Swain|first4=S. D.|last5=Hoppeler|first5=H.|last6=Navarro|first6=V.|doi=10.1038/353748a0|bibcode=1991Natur.353..748L|s2cid=4363282}}</ref>

==Limiting factors==
The factors affecting V̇O<sub>2</sub> may be separated into supply and demand.<ref name=bassett1>{{cite journal |author1=Bassett D.R Jr. |author2=Howley E.T. | year = 2000 | title = Limiting factors for maximum oxygen uptake and determinants of endurance performance | journal = Med Sci Sports Exerc | volume = 32 | issue = 1| pages = 70–84 | doi=10.1097/00005768-200001000-00012|pmid=10647532 | doi-access = free }}</ref> Supply is the transport of oxygen from the lungs to the [[mitochondria]] (combining [[pulmonary function]], [[cardiac output]], [[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]].<ref name=bassett1 /> Of these, the supply factors may be more limiting.<ref name=bassett1 /><ref name="bassett2" /> However, it has also been argued that while trained subjects are probably supply limited, untrained subjects can indeed have a demand limitation.<ref name=Newideas>{{cite journal | author = Wagner P.D. | year = 2000 | title = New ideas on limitations to VO2max | journal = Exercise and Sport Sciences Reviews | volume = 28 | issue = 1| pages = 10–4 | pmid = 11131681 }}</ref>

General characteristics that affect V̇O<sub>2</sub> max include age, [[Sex differences in human physiology|sex]], fitness and training, and altitude. V̇O<sub>2</sub> max can be a poor predictor of performance in runners due to variations in [[running economy]] and [[fatigue (medical)|fatigue]] resistance during prolonged exercise. The body works as a system. If one of these factors is sub-par, then the whole system's normal capacity is reduced.<ref name="Newideas"/>

The drug [[erythropoietin]] (EPO) can boost V̇O<sub>2</sub> max by a significant amount in both humans and other mammals.<ref>{{cite journal | author = Kolb E. M. | year = 2010 | title = Erythropoietin elevates V.O2, max but not voluntary wheel running in mice | journal = Journal of Experimental Biology | volume = 213 | issue = 3| pages = 510–519 | doi=10.1242/jeb.029074| pmid = 20086137 | doi-access =  }}</ref> This makes EPO attractive to athletes in [[endurance sport]]s, such as professional cycling. EPO has been [[Erythropoietin#Usage as doping product|banned since the 1990s]] as an illicit [[performance-enhancing substance]], but by 1998 it had become widespread in cycling and led to the [[Festina affair]]<ref>{{cite journal |author1=Lundby C. |author2=Robach P. |author3=Boushel R. |author4=Thomsen J. J. |author5=Rasmussen P. |author6=Koskolou M. |author7=Calbet J. A. L. | year = 2008 | title = Does recombinant human Epo increase exercise capacity by means other than augmenting oxygen transport? | journal = Journal of Applied Physiology | volume = 105 | issue = 2|pages=581–7 | doi = 10.1152/japplphysiol.90484.2008 | pmid=18535134|hdl=10553/6534 |hdl-access=free }}</ref><ref name=lode1>{{cite journal |author1=Lodewijkx Hein F.M. |author2=Brouwer Bram | year = 2011 | title = Some Empirical Notes on the Epo Epidemic in Professional Cycling| url = https://www.academia.edu/1129538 | journal = Research Quarterly for Exercise and Sport| volume = 82 | issue = 4| pages = 740–754 | doi = 10.5641/027013611X13275192112069 | pmid=22276416}}</ref> as well as being mentioned ubiquitously in the [[USADA]] 2012 report on the [[U.S. Postal Service Pro Cycling Team]].<ref>{{Cite web|date=October 2012|title=U.S. Postal Service Pro Cycling Team Investigation|url=https://www.usada.org/athletes/results/u-s-postal-service-pro-cycling-team-investigation/|access-date=4 January 2023|website=[[USADA]]|language=en-US}}</ref> [[Greg LeMond]] has suggested establishing a baseline for riders' V̇O<sub>2</sub> max (and other attributes) to detect abnormal performance increases.<ref>{{Cite web|title=Greg LeMond's suggestions for a credible future for cycling|author=Conal Andrews|url=http://www.velonation.com/News/ID/5050/Greg-LeMonds-suggestions-for-a-credible-future-for-cycling.aspx|date=July 28, 2010|access-date=4 January 2023|website=velonation.com}}</ref>

==Clinical use to assess cardiorespiratory fitness and mortality==
V̇O<sub>2</sub> max/peak is widely used as an indicator of cardiorespiratory fitness (CRF) in select groups of athletes or, rarely, in people under assessment for disease risk. In 2016, the [[American Heart Association]] (AHA) published a scientific statement recommending that CRF {{ndash}} quantifiable as V̇O<sub>2</sub> max/peak {{ndash}} be regularly assessed and used as a clinical vital sign; ergometry (exercise wattage measurement) may be used if V̇O<sub>2</sub> is unavailable.<ref name="ross">{{cite journal |last1=Ross |first1=Robert |last2=Blair |first2=Steven N. |last3=Arena |first3=Ross |last4=Church |first4=Timothy S. |last5=Després |first5=Jean-Pierre |last6=Franklin |first6=Barry A. |last7=Haskell |first7=William L. |last8=Kaminsky |first8=Leonard A. |last9=Levine |first9=Benjamin D. |last10=Lavie |first10=Carl J. |last11=Myers |first11=Jonathan |last12=Niebauer |first12=Josef |last13=Sallis |first13=Robert |last14=Sawada |first14=Susumu S. |last15=Sui |first15=Xuemei |last16=Wisløff |first16=Ulrik|display-authors=3 |title=Importance of Assessing Cardiorespiratory Fitness in Clinical Practice: A Case for Fitness as a Clinical Vital Sign: A Scientific Statement From the American Heart Association |journal=Circulation |date=13 December 2016 |volume=134 |issue=24 |pages=e653–e699 |doi=10.1161/CIR.0000000000000461 |pmid=27881567 |s2cid=3372949 |doi-access=free }}</ref> This statement was based on evidence that lower fitness levels are associated with a higher risk of cardiovascular disease, all-cause mortality, and mortality rates.<ref name=ross/> In addition to risk assessment, the AHA recommendation cited the value for measuring fitness to validate [[exercise prescription]]s, [[Physical exercise|physical activity]] counseling, and improve both management and health of people being assessed.<ref name=ross/>

A 2023 [[meta-analysis]] of [[Observational study|observational]] [[Cohort study|cohort studies]] showed an inverse and independent association between V̇O<sub>2</sub> max and all-cause mortality risk.<ref name=lauk/> Every one [[Metabolic equivalent of task|metabolic equivalent]] increase in estimated cardiorespiratory fitness was associated with an 11% reduction in mortality.<ref name=lauk/> The top third of V̇O<sub>2</sub> max scores represented a 45% lower mortality in people compared with the lowest third.<ref name="lauk">{{Cite journal |last1=Laukkanen |first1=Jari A. |last2=Isiozor |first2=Nzechukwu M. |last3=Kunutsor |first3=Setor K. |date=2022 |title=Objectively Assessed Cardiorespiratory Fitness and All-Cause Mortality Risk |url=https://research-information.bris.ac.uk/files/314942003/CRF_Mortality_Final.pdf |journal=Mayo Clinic Proceedings |language=en |volume=97 |issue=6 |pages=1054–1073 |doi=10.1016/j.mayocp.2022.02.029|pmid=35562197 |s2cid=248737752 }}</ref>

As of 2023, V̇O<sub>2</sub> max is rarely employed in routine clinical practice to assess cardiorespiratory fitness or mortality due to its considerable demand for resources and costs.<ref>{{Cite journal |last1=Kaminsky |first1=Leonard A. |last2=Imboden |first2=Mary T. |last3=Ozemek |first3=Cemal |date=2023 |title=It's Time to (Again) Recognize the Considerable Clinical and Public Health Significance of Cardiorespiratory Fitness |url=https://linkinghub.elsevier.com/retrieve/pii/S0735109723002978 |journal=Journal of the American College of Cardiology |language=en |volume=81 |issue=12 |pages=1148–1150 |doi=10.1016/j.jacc.2023.02.004|pmid=36948730 |s2cid=257649017 |doi-access=free }}</ref><ref>{{Cite journal |last1=Lavie |first1=Carl J. |last2=Arena |first2=Ross |last3=Kaminsky |first3=Leonard A. |date=2022 |title=Making the Case to Measure and Improve Cardiorespiratory Fitness in Routine Clinical Practice |journal=Mayo Clinic Proceedings |language=en |volume=97 |issue=6 |pages=1038–1040 |doi=10.1016/j.mayocp.2022.04.011|pmid=35570068 |doi-access=free }}</ref>

== History ==
British physiologist [[Archibald Hill]] introduced the concepts of maximal oxygen uptake and oxygen debt in 1922.<ref>{{cite journal |last1=Hale |first1=Tudor |title=History of developments in sport and exercise physiology: A. V. Hill, maximal oxygen uptake, and oxygen debt |journal=Journal of Sports Sciences |date=15 February 2008 |volume=26 |issue=4 |pages=365–400 |doi=10.1080/02640410701701016 |pmid=18228167 |s2cid=33768722 }}</ref><ref name="bassett2">{{cite journal |last1=Bassett |first1=David R. |last2=Howley |first2=Edward T. |title=Maximal oxygen uptake: 'classical' versus 'contemporary' viewpoints |journal=Medicine &amp Science in Sports &amp Exercise |date=May 1997 |volume=29 |issue=5 |pages=591–603 |doi=10.1097/00005768-199705000-00002 |pmid=9140894 |doi-access=free }}</ref> Hill and German physician [[Otto Fritz Meyerhof|Otto Meyerhof]] shared the 1922 [[Nobel Prize in Physiology or Medicine]] for their independent work related to muscle energy metabolism.<ref>{{Cite web|url=https://www.nobelprize.org/prizes/medicine/1922/summary/|title=The Nobel Prize in Physiology or Medicine 1922|publisher=Nobel Foundation|language=en-US|access-date=11 October 2018}}</ref> Building on this work, scientists began measuring oxygen consumption during exercise. Key contributions were made by Henry Taylor at the [[University of Minnesota]], Scandinavian scientists [[Per-Olof Åstrand]] and [[Bengt Saltin]] in the 1950s and 60s, the [[Harvard Fatigue Laboratory]], German universities, and the Copenhagen Muscle Research Centre.<ref>{{Cite journal|last=Seiler|first=Stephen|year=2011|title=A Brief History of Endurance Testing in Athletes|url=http://www.sportsci.org/2011/ss.pdf|journal=Sportscience|volume=15|issue=5}}</ref><ref>{{Cite web|url=https://uk.humankinetics.com/products/history-of-exercise-physiology|title=History of Exercise Physiology|website=Human Kinetics Europe|access-date=11 October 2018}}</ref>

==See also==

*[[Anaerobic exercise]]
*[[Arteriovenous oxygen difference]]
*[[Cardiorespiratory fitness]]
*[[Comparative physiology]]
*[[Oxygen pulse]]
*[[Respirometry]]
*[[Running economy]]
*[[Training effect]]
*[[Jack Daniels (coach)#VDOT|VDOT]]
*[[vVO2max|vVO<sub>2</sub>max]]

==References==
{{Reflist}}

{{DEFAULTSORT:Vo2 Max}}
[[Category:Exercise biochemistry]]
[[Category:Sports terminology]]
[[Category:Respiratory physiology]]