Energy systems: Factors affecting VO₂ max/aerobic power.

The idea

VO₂ max, also called aerobic power, is the maximum rate at which the body can take up, transport and use oxygen during intense exercise. It can be expressed as an absolute value in litres per minute (L/min) or as a relative value in millilitres of oxygen per kilogram of body mass per minute (ml·kg⁻¹·min⁻¹). Several factors affect it. Genetic makeup sets a ceiling, while training can improve it. Age and sex influence typical values: young adults often have higher values than older adults, and males often have higher values than females. Body composition matters because a higher proportion of lean muscle mass supports a greater VO₂ max. The efficiency of the cardiovascular and respiratory systems, including cardiac output, stroke volume, haemoglobin concentration and muscle capillary density, also affects oxygen delivery and use.

What earns the marks

• VO₂ max is the maximum rate of oxygen uptake, transport and use during exercise, expressed in L/min (absolute) or ml·kg⁻¹·min⁻¹ (relative).
• Genetic makeup sets an individual's upper limit for VO₂ max.
• Training, especially aerobic training, can increase VO₂ max by improving cardiac output, stroke volume and capillary density.
• Age and sex affect typical VO₂ max values: it tends to be higher in young adults and often higher in males than females.
• Body composition, particularly a high proportion of lean muscle mass, is associated with a higher VO₂ max.
• Cardiovascular and respiratory efficiency, including haemoglobin concentration and oxygen delivery, influences VO₂ max.

Common mistakes and how to put them right

• Confusing VO₂ max with lung volume.

  Put it right: VO₂ max depends on oxygen uptake, transport and use, not just how much air the lungs can hold.

• Thinking VO₂ max is fixed and cannot change.

  Put it right: Training can improve it, although genetics set an upper limit.

• Believing VO₂ max is the same for everyone of the same age.

  Put it right: Sex, body composition and training status also cause differences.

• Assuming VO₂ max can only be measured in one way.

  Put it right: It can be absolute (L/min) or relative to body mass (ml·kg⁻¹·min⁻¹).

Exam tips

• Check whether the question asks for a factor that affects VO₂ max or for the definition of VO₂ max.
• When a factor is given, link it to oxygen delivery or use rather than just naming it.
• Remember that both genetic and training factors can affect VO₂ max, so avoid options that say only one matters.
• Pay attention to the units provided: L/min for absolute VO₂ max and ml·kg⁻¹·min⁻¹ for relative VO₂ max.