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VO2 max (also maximal oxygen consumption, maximal oxygen uptake, peak oxygen uptake or maximal aerobic capacity) is the maximum rate of oxygen consumption as measured during incremental exercise, most typically on a motorized treadmill. [1][2] Maximal oxygen consumption reflects the aerobic physical fitness of the individual, and is an important determinant of their endurance capacity during prolonged, sub-maximal exercise. The name is derived from V - volume, O2 - oxygen, max - maximum.

VO2 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 body mass per minute (e.g., mL/(kg·min)). The latter expression is often used to compare the performance of endurance sports athletes. However, VO2 max generally does not vary linearly with body mass, either among individuals within a species or among species,[1][2] 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.

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:

VO2 max = Q x (CaO2 - CvO2), 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. [3]

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–Sorensen–Overgard–Pedersen estimation

Another estimate of VO2 max for humans, based on maximum and resting heart rates, was created by a group of researchers from Denmark. [4] It is given by:

VO2 max ~15*(mL /kg*min)* (HRmax/HRrest)

This equation uses maximum heart rate (HRmax) and resting heart rate (HRrest) to estimate VO2 max.

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/(kg·min)] is:[5]

VO2 max~ (d12 - 504.9) \ 44.73

where d12 is distance (in metres) covered in 12 minutes, alternatively

VO2 max~(35.97 * dmiles12) - 11.29

where d12 is distance (in miles) covered in 12 minutes,

Multi-stage fitness test

VO2 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 body mass per minute (e.g., mL/(kg·min)). The latter expression is often used to compare the performance of endurance sports athletes. However, VO2 max generally does not vary linearly with body mass, either among individuals within a species or among species,[1][2] 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.

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:

VO2 max = Q x (CaO2 - CvO2), 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. [3]

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–Sorensen–Overgard–Pedersen estimation

Another estimate of VO2 max for humans, based on maximum and resting heart rates, was created by a group of researchers from Denmark. [4] It is given by:

VO2 max ~15*(mL /kg*min)* (HRmax/HRrest)

This equation uses maximum heart rate (HRmax) and resting heart rate (HRrest) to estimate VO2 max.

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/(kg·min)] is:[5]

VO2 max~ (d12 - 504.9) \ 44.73

where d12 is distance (in metres) covered in 12 minutes, alternatively

VO2 max~(35.97 * dmiles12) - 11.29

where d12 is distance (in miles) covered in 12 minutes,

Multi-stage fitness test

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