What is maximal oxygen uptake (VO2 max)?

From the Guidelines

VO2 max is the maximum amount of oxygen your body can use during intense exercise, measured in milliliters of oxygen per kilogram of body weight per minute, and is a key indicator of cardiorespiratory fitness and aerobic capacity. This measurement is influenced by genetics, but can be improved through regular aerobic exercise like running, cycling, or swimming 1. According to the most recent study in 2023, VO2 max is determined by how efficiently your body delivers and uses oxygen, involving your heart, lungs, blood vessels, and muscles working together 1.

Key Factors Influencing VO2 Max

• Genetics: about 50% of VO2 max is influenced by genetics 1
• Age: VO2 max declines with age, with an average decline of 10% per decade in non-athletic subjects 1
• Sex: VO2 max is generally higher in men than women, due to differences in hemoglobin concentration, muscle mass, and stroke volume 1
• Exercise habits: regular aerobic exercise can improve VO2 max, with high-intensity interval training (HIIT) being particularly effective 1

Improving VO2 Max

• Regular aerobic exercise: running, cycling, or swimming can improve VO2 max 1
• High-intensity interval training (HIIT): can improve VO2 max in as little as 4-12 weeks of consistent training 1
• Elite endurance athletes: often have VO2 max values of 70-85 ml/kg/min, while average adults range from 30-45 ml/kg/min 1

Clinical Significance of VO2 Max

• VO2 max is a key indicator of cardiorespiratory fitness and aerobic capacity 1
• Improving VO2 max can enhance athletic performance, reduce disease risk, and improve overall quality of life 1
• VO2 max is an important prognostic marker in patients with cardiovascular disease, with higher values indicating better outcomes 1

From the Research

Definition of Maximal Oxygen Uptake (VO2 max)

• Maximal oxygen uptake (VO2 max) is defined as the oxygen uptake attained during maximal exercise intensity that could not be increased despite further increases in exercise workload, thereby defining the limits of the cardiorespiratory system 2.
• It is the single most important factor for long-distance running performance 3.
• VO2 max is a valid index measuring the limits of the cardiorespiratory systems' ability to transport oxygen from the air to the tissues at a given level of physical conditioning and oxygen availability 2.

Limiting Factors for VO2 max

• The ability of the cardiorespiratory system to deliver oxygen to the exercising muscles is the primary limiting factor for VO2 max in exercising humans 4.
• Oxygen delivery, not skeletal muscle O2 extraction, is viewed as the primary limiting factor for VO2 max in exercising humans 4.
• Maximal cardiac output is a key determinant of VO2 max, and increases in maximal cardiac output result in increases in VO2 max 4, 5.

Determinants of Endurance Performance

• VO2 max is an important variable that sets the upper limit for endurance performance, as an athlete cannot operate above 100% VO2 max for extended periods 4.
• Running economy and fractional utilization of VO2 max also affect endurance performance 4.
• The speed at lactate threshold integrates all three of these variables and is the best physiological predictor of distance running performance 4.

Effects of High-Intensity Interval Training on VO2 max

• High-intensity interval training (HIIT) can improve VO2 max by increasing cardiac output and maximal oxygen uptake 3, 5, 6.
• The increase in VO2 max seen in response to HIIT is due to improvements in oxygen delivery 5.
• The cardiovascular adaptation after high-frequency training is delayed compared to training with moderate frequency 6.