VO₂ max

VO₂ max measurement using instruments on a modern metabolic cart during a graded treadmill exercise test

Gas exchange of VO₂ and VCO₂ during max test. Begin for 3 mins at 60 watts and add 35 watts every 3 minutes until exhaustion

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 a steady state despite an increase in workload.

VO₂ max is properly defined by the Fick equation:

${\displaystyle \mathrm {VO_{2}\;max} =Q\times \ (\mathrm {C_{a}O_{2}} -\mathrm {C_{v}O_{2}} )}$, when these values are obtained during an exertion at a maximal effort.

where Q is the cardiac output of the heart, C_aO₂ is the arterial oxygen content, and C_vO₂ is the venous oxygen content.

(C_aO₂ – C_vO₂) is also known as the arteriovenous oxygen difference.[4]

An estimate of VO₂ max is based on maximum and resting heart rates.[5] It is given by:

${\displaystyle {\text{V}}{\ce {O2}}{\text{ max}}\approx {\frac {{\text{HR}}_{\text{max}}}{{\text{HR}}_{\text{rest}}}}\times 15.3{\text{ mL}}/({\text{kg·minute}}).}$

This equation uses the ratio of maximum heart rate (HR_max) to resting heart rate (HR_rest) to predict VO₂ 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.

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/(kg·min)] is:[6]

${\displaystyle \mathrm {VO_{2}\;max} \approx {d_{12}-504.9 \over 44.73}}$

where d₁₂ is distance (in metres) covered in 12 minutes.

An alternative equation is:

${\displaystyle \mathrm {VO_{2}\;max} \approx {(35.97*d'_{12})-11.29}}$

where d'₁₂ is distance (in miles) 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 beep test).[7]

Estimation of VO₂ max from a timed one-mile track walk with duration t, incorporating gender, age, body weight in pounds (BW), and heart rate (HR) at the end of the mile.[8] The constant x is 6.3150 for males, 0 for females. BW is in lbs, time is in minutes.

${\displaystyle \mathrm {VO_{2}\;max} \approx 132.853-0.0769BW-0.3877{\text{age}}-3.2649t-0.1565HR+x}$

The Firstbeat method of VO₂ max estimation, of which a patent application was filed in 2012,[9] is widely licensed and used in consumer technology applications.[10] The first consumer fitness device using the Firstbeat method of VO₂ max estimation was the Garmin Forerunner 620, released in 2013.[11] Since then, Suunto, Jabra, Huawei, and PulseOn[12] have also introduced products that use the Firstbeat method.[13]

The method relies on an analysis of the linear relationship between oxygen consumption and running speed, meaning that the oxygen cost of running increases when running speed increases. To facilitate analysis and enhance accuracy, timed segments of recorded activity data are identified on the basis of heart rate ranges and reliability; only the most reliable segments are used. This allows the method to be applied to freely performed running, walking and cycling activities and diminishes the need for dedicated fitness testing protocols. The calculation requires user basic anthropometric data (age, gender, height, weight, etc.), heartbeat data (internal workload), and a measure of external workload.[14]

• External workload running/walking: movement speed obtained from either GPS or accelerometer sensors
• External workload cycling: power output expressed in watts and measured by a power meter.

VO₂ max estimates provided by the Firstbeat method are most accurate during running activities that use GPS to capture external workload data. This combination has been validated to be 95% accurate compared to laboratory testing.[14] Because the Firstbeat estimation method is sub-maximal in nature, accuracy of the estimate is strongly tied to validity of the HRmax value used in the calculation.[14]

The average untrained healthy male has a VO₂ max of approximately 35–40 mL/(kg·min).[15][16] The average untrained healthy female has a VO₂ max of approximately 27–31 mL/(kg·min).[15] 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 never 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).[17] 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).[18] 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), when aged 18.[19]

The highest values in absolute terms for humans 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.[20] 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 reported to have had a VO₂ of 7.5 L/min[21] . He also had a lung capacity of 8.5 litres.[22] New Zealand sculler Rob Waddell has one of the highest absolute VO2 max levels ever tested.[23] These VO2max figures are absolute figures (ie the total amount of oxygen metabolised in a minute). Rowers tend to be more interested in absolute VO2max whereas runners are generally more interested in relative VO2 max (ie the total amount of oxygen metabolised per minute per kilogram of body weight)[24].

VO₂ max has been measured in other animal species. During loaded swimming, mice had a VO₂ max of around 140 mL/(kg·min),[25] Thoroughbred horses had a VO₂ max of around 193 mL/(kg·min) after 18 weeks of high-intensity training.[26] Alaskan huskies running in the Iditarod Trail Sled Dog Race had VO₂ max values as high as 240 mL/(kg·min).[27] Estimated VO₂ max for pronghorn antelope was as high as 300 mL/(kg·min).[28]