Aerobic capacity
The body's overall ability to take in, transport and use oxygen to produce energy.
Aerobic capacity is your body's overall ability to take in oxygen, transport it and use it to make energy. Measured at its ceiling it is VO2max; described as a quality it is the whole chain from lungs to mitochondria working together.
Every link in that chain can limit you. Lungs load oxygen into blood, the heart pumps it, haemoglobin carries it, capillaries deliver it, and mitochondria burn fuel with it. In healthy people the pump is usually the bottleneck, which is why cardiac adaptations dominate the early gains from endurance training.
It matters beyond sport. Cardiorespiratory fitness is among the strongest single predictors of how long people live: in a cohort of 122,007 people who underwent treadmill testing, mortality fell steadily as fitness rose, with no ceiling to the benefit and the steepest part of the curve at the bottom.
Improving it takes both easy volume and hard work. Large amounts of comfortable aerobic training build the peripheral machinery and the tolerance to train more, while intervals near maximum stress the central pump. Programmes that use only one end of the range leave something on the table.
It responds quickly and fades quickly. Meaningful gains appear within weeks of consistent training, and a good deal is lost over a few weeks of doing nothing, which is a fair argument for consistency over intensity.
Age reduces it, and training reduces the reduction. A reference study of 4,631 healthy adults aged 20 to 90 found a mean peak oxygen uptake of 40.0 mL/kg/min, with values declining through the decades and, at every age, lower values tracking with clustered cardiovascular risk factors.
In practice, estimate it with our VO2max calculator, train the two ends of the intensity range with our heart rate zone calculator, and judge yourself against your own trajectory rather than against a table.
Sources
- Mandsager K, et al. Association of Cardiorespiratory Fitness With Long-term Mortality Among Adults Undergoing Exercise Treadmill Testing. JAMA Netw Open 2018;1(6):e183605
- Aspenes ST, et al. Peak oxygen uptake and cardiovascular risk factors in 4631 healthy women and men. Med Sci Sports Exerc 2011;43:1465-1473