Oxygen Uptake

Oxygen uptake is commonly referred to as VO₂, which stands for the volume (V) of oxygen (O₂) being consumed by the body. VO₂ is measured in liters of oxygen per minute (L/min) and therefore represents the rate at which oxygen is being consumed by metabolically active tissues (e.g., muscle).

Oxygen uptake can be used to calculate total body energy expenditure using a method known as indirect calorimetry. Though VO₂ can be measured at rest, it’s more commonly measured during exercise.

When oxygen uptake is measured during an exercise test performed to exhaustion, we can determine someone’s VO₂max — the maximal rate at which the body can consume oxygen during exercise.

VO₂max is seen as the single best indicator of cardiorespiratory or aerobic fitness because as you become fitter, your body becomes better at using oxygen to produce energy and your VO₂max increases. However, a higher VO₂max doesn’t always translate to improved exercise or sports performance because some activities involve moments when energy requirements are so great (the intensity is so high) that oxygen isn’t used to generate the required energy. This is known as anaerobic (“without oxygen”) exercise.

Elite endurance athletes often have a very high VO₂max, but this is just one aspect that determines aerobic exercise performance. Furthermore, oxygen uptake is also recognized as an important factor in healthspan and longevity, and having a higher VO₂ max is associated with reduced all-cause mortality.^[1]