X-ray showing air under diaphragm

Take a deep breath

How do we measure how much oxygen we can use?

Work your muscles hard, and you will need more oxygen. Your brain’s respiratory centre sends signals to the diaphragm and intercostal muscles to breathe more air in and expel it faster, affecting how deeply and how fast you breathe. However, these aren’t the only factors affecting how much oxygen you can use. 

Table: Different physiological measures for average men and women versus elite cyclists

Measure Average man Average woman Elite cyclist*
Total lung capacity (litres) 6 4.2 8
VO2 max (ml/kg/min) 45 38 88
Resting heart rate (beats/min) 64–72 72–80 28

Miguel Indurain, who won five consecutive Tours de France
Source: Data from BBC News and ‘Cycling Weekly’

 

Also important is how fast and how much blood your heart can pump, how dense the red cells (which carry oxygen) are in your blood, how efficient the blood supply is to your muscles, and how efficiently your muscles can use the oxygen.

VO2 max is a measure of the maximum amount of oxygen (in millilitres) you can use per kilogram of body weight per minute. Men who do not train average around 45 ml/kg/min, and it is slightly lower for women, at 38 ml/kg/min (see table). Athletes commonly record values in the 70s, and a few exceptional people may reach into the 90s. The highest values have been seen in cross-country skiers.

Fast animals can have a much higher VO2 max than humans. Thoroughbred horses often reach 180 ml/kg/min; sled dogs, bred for strength and endurance, can register 240 ml/kg/min; and the pronghorn antelope beats them all with 300 ml/kg/min.

VO2 max is not the only thing that determines top speed. You have to dissipate heat from your muscles, for example. This is easier for a mouse, which has a high surface area relative to its mass, than a human. However, VO2 is a good measure of general fitness.

Lead image:

X-ray showing air under the diaphragm.

Wellcome Images CC BY NC ND

References

Further reading

About this resource

This resource was first published in ‘Exercise, Energy and Movement’ in January 2012 and reviewed and updated in August 2016.

Topics:
Cell biology, Statistics and maths, Physiology, Health, infection and disease
Issue:
Exercise, Energy and Movement
Education levels:
14–16, 16–19, Continuing professional development