Introduction
VO2 Max, or maximal oxygen uptake, is widely regarded as the definitive measure of cardiovascular fitness and aerobic endurance. It represents the maximum amount of oxygen an individual can utilise during intense, exhaustive exercise and is a key indicator of one’s aerobic capacity. It is therefore also a key indicator of human health.
Physiological Relevance
VO2 Max is expressed in millilitres of oxygen used in one minute per kilogram of body weight (ml/kg/min). It reflects the efficiency of the body to transport and use oxygen during exercise, integrating the performance of the heart, lungs, blood vessels, and muscles. Higher VO2 Max values indicate greater physical fitness and better aerobic endurance.
VO2 Max is fundamentally linked to the physiological efficiency of various body systems working in concert during strenuous exercise to transport oxygen to muscle tissues and the capacity of muscle cells to generate energy from the supply of oxygen. The cardiovascular system provides the delivery mechanism, while muscles use the oxygen they receive to create energy in mitochondria, the cellular engines. Exercise is not only the beneficiary of these systems but also the means by which they become more efficient, as the building of muscle improves the effectiveness of the cardiovascular system and increases the number of mitochondria, both through higher muscle mass and increased populations in individual cells.
The endocrine system plays a role too by regulating metabolism through the release of hormones such as adrenaline, which increases heart rate and the hence the flow of blood, the transporter of oxygen, to the muscles.
VO2 Max Testing Methods and Measurements
Laboratory Testing
The most accurate method for measuring VO2 Max involves a graded exercise test in a controlled laboratory setting. Typically the test is performed on a treadmill or a stationary bike. The participant wears a mask or a mouthpiece connected to a metabolic cart. This setup measures the volume and gas concentrations of inhaled and exhaled air.
The primary measurements include the volume of oxygen consumed and the volume of carbon dioxide produced during exercise by comparing the inhaled air composition with the exhaled air composition. The test begins at a low intensity, which gradually increases until the participant reaches exhaustion or cannot continue due to fatigue.
VO2 Max is calculated as the highest amount of oxygen the body is capable of utilising during maximum physical effort. The ratio of carbon dioxide produced to oxygen consumed is also analysed, providing insights into aerobic and anaerobic threshold. Exercise intensity is gradually increased to the point where oxygen consumption eventually reaches a plateau, indicating that VO2 Max has been reached.
Field Tests
Field tests for estimating VO2 Max are more practical and less equipment-intensive. Common tests include the Cooper run test (running as far as possible in 12 minutes) or the Beep test (progressive shuttle run).
These tests usually measure the distance covered or the stage/level reached during the test. They don't directly measure oxygen consumption.
The results (distance or level achieved) are then input into standardised equations that estimate VO2 Max based on the correlation between physical performance and aerobic capacity. For instance, the distance covered in the Cooper test correlates strongly with VO2 Max, allowing for an estimated measurement.
Wearable Technology
Advanced fitness trackers and smartwatches estimate VO2 Max using algorithms that incorporate data such as heart rate, speed, and sometimes even altitude and temperature.
These devices primarily use heart rate data during exercise, coupled with user metrics like age, gender, weight, and fitness level. Some wearables also measure heart rate variability, speed, and other performance metrics during activity.
The devices apply proprietary algorithms to estimate VO2 Max. The accuracy of these estimates varies but has been improving with advancements in technology. They don't directly measure oxygen and carbon dioxide levels but provide an estimated VO2 Max value based on heart rate and other performance metrics during physical activity.
In summary, laboratory testing provides the most accurate VO2 Max measurement by directly measuring oxygen and carbon dioxide levels during incremental exercise to exhaustion. Field tests offer a practical but less precise estimation based on physical performance, while wearable technology provides convenient, though indirect, estimates using heart rate and activity data.
Impact of Different Types of Exercise
Aerobic Exercises
Activities like running, cycling, and swimming are most effective in increasing VO2 Max. High-Intensity Interval Training (HIIT) particularly stands out for its efficiency in improving VO2 Max within a short time frame.
Resistance Training
While traditionally associated with strength rather than aerobic capacity, resistance training can also contribute to VO2 Max improvements, especially when it includes circuit training with short rest breaks between sets, essentially a form of High Intensity Interval Training.
Incorporating both aerobic and resistance training in a fitness regime can provide a comprehensive boost to VO2 Max.
Time Efficiency and Stress Avoidance
High Intensity Interval Training (HIIT)
High-Intensity Interval Training is highly time-efficient, requiring shorter durations compared to steady-state cardio exercises. HIIT sessions can last for about 20-30 minutes and still offer significant improvements in VO2 Max. Based on key research studies, HIIT also provides the following very significant health-related adaptations:
- Reduced Blood Pressure
- Improved Insulin Sensitivity
- Increased Nitric Oxide Availability
- Improved Lipid Metabolism
- Increased Muscle Mitochondria Biogenesis
High Intensity Interval Training requires activity which raises the heart rate into the Anaerobic and VO2 Max exercise zones which start at around 80% and 90% of maximum beats per minute.
Low-Impact Aerobic Exercise
Activities like brisk walking, cycling, and swimming are less stressful on the joints and reduce the risk of injury, making them suitable for individuals at different fitness levels. All of these activities can be extended into High Intensity Interval Training by increasing intensity for short periods.
VO2 Max and Supplements
As with all aspects of health, we suggest that supplements are considered, in consultation with healthcare professionals, as one component of a regimen that incorporates all lifestyle elements including exercise (physical and mental), nutrition, sleep, stress management and social interaction). Rather than looking for supplements that could impact VO2 Max directly (for which there seems to be scant evidence), it would likely be more constructive to consider the positive long term effect which factors such as favourable omega-3 to omega-6 PUFA ratios can exert on cardiovascular health, which is central to oxygen usage capacity.
Conclusion
VO2 Max is a crucial measure of an individual's aerobic fitness and an importnt predictor of overall health and longevity. Various forms of exercise, particularly those combining aerobic, anaerobic activity and resistance training, are effective in improving VO2 Max. Emphasising time-efficient and low-impact exercises can make VO2 Max improvement accessible to a broader population, enhancing both health and quality of life.
Key Studies
The Physiology of Interval Training: A New Target to HIIT (Andrea Nicolo, Michele Girardi)
Books
Outlive: The Science and Art of Longevity (Peter Attia MD)
Videos
BNC#5: Tim Noakes uncovers medical scams, shatters misconceptions around diabetes, statins & more
https://www.youtube.com/watch?v=uFZIv_BavZM