VO₂ max is increasingly recognised as one of the most valuable objective measures of long-term health and functional ageing. It reflects how efficiently the body uses oxygen during exercise, integrating cardiovascular, respiratory and muscular performance into a single measurable marker. In practical terms, it is a measure of cardiorespiratory fitness.
What is VO₂ max?
VO₂ max is the maximum rate at which your body can take in, transport and utilise oxygen to produce energy during exercise. It reflects how efficiently your heart, lungs and muscles work together to deliver and use oxygen to meet the demands of exercise.
VO₂ max is widely regarded as the criterion measure of cardiorespiratory fitness. It may be reported as an absolute value in litres per minute or relative to body mass in millilitres per kilogram per minute. The relative measure is commonly used to compare results between people of different sizes.
This is an integrated measure, not a test of one organ in isolation. A result can be influenced by the ability of the lungs to take in oxygen, the heart and circulation to transport it, and the muscles to extract and use it. Age, sex, genetics, health conditions, medication, body composition and training history can also affect the result.
Why is VO₂ max important?
Cardiorespiratory fitness is increasingly recognised as one of the most powerful predictors of long-term health and survival. Unlike many risk factors, it is also highly modifiable.
Large studies involving more than 120,000 participants have shown substantially higher mortality rates among individuals with low aerobic fitness compared with those with higher fitness levels. The strongest long-term outcomes were consistently observed among those with high cardiorespiratory fitness, including older populations.
Importantly, the relationship appears continuous. Even modest improvements in VO₂ max are associated with measurable reductions in cardiovascular risk and all-cause mortality. These studies show a strong association; they do not prove that raising one test score will by itself extend an individual’s life.
This is clinically significant because fitness reflects far more than exercise performance. It is an integrated measure of cardiovascular, respiratory, metabolic and muscular function. Unlike age or genetics, cardiorespiratory fitness can often be improved. Regular aerobic exercise can lead to meaningful improvements in VO₂ max at almost any age, although the response varies between individuals.
Why test your VO₂ max?
Many people exercise regularly without knowing whether they are training at the intensity best suited to their goals. Measuring VO₂ max provides an objective assessment of current cardiovascular fitness and can help:
- Establish personalised exercise intensity and heart-rate training zones.
- Monitor changes in fitness over time.
- Guide exercise prescription for health, fitness or performance.
- Compare cardiorespiratory fitness with age- and sex-specific reference values.
One of the major advantages of VO₂ max assessment is that it provides an objective marker that can be tracked longitudinally as part of preventative health care. Preventative medicine should not only identify disease once it occurs. It should also measure physiological capacity before decline becomes clinically significant.
How is VO₂ max measured?
At Executive Medicine, VO₂ max is measured during a graded treadmill exercise test, where the intensity progressively increases until you reach your maximum effort. A specialised face mask continuously measures the oxygen you consume and the carbon dioxide you produce, providing an accurate assessment of your cardiorespiratory fitness.
Heart rate, symptoms and the response to increasing workload are monitored throughout the test. The protocol and the decision to stop should be guided by the person’s health, exercise history, symptoms and measured responses.
In some people, a clear plateau in oxygen uptake appears despite a further increase in workload. In others, supporting criteria and clinical judgement are used to assess whether a maximal effort was achieved. When a true maximum cannot be confirmed, the highest measured value may be more accurately described as VO₂ peak.
Measured VO₂ max versus a watch estimate
Fitness watches, submaximal exercise tests and prediction equations usually estimate VO₂ max rather than measure respiratory gases directly. Their algorithms may use heart rate, speed, distance, age, sex, body size and self-reported activity. These tools can be convenient and may be useful for observing broad trends, particularly when the same device and conditions are used consistently.
They do not directly measure how much oxygen the body is consuming. Research suggests that exercise-based wearable estimates may perform reasonably at a population level, but individual error can be substantial. Heart-rate accuracy, terrain, temperature, fatigue, medication, the chosen activity and the device’s algorithm can all affect the estimate.
- A laboratory or clinical test measures respiratory gas exchange during graded exercise.
- A wearable or equation predicts VO₂ max from indirect inputs and assumptions.
- An estimate can help track a trend, but it should not be treated as equivalent to a directly measured result when clinical or precise training decisions are involved.
Understanding your result
Comparing a result with age- and sex-specific reference values can show where it sits within a relevant population. However, a percentile is not a pass-or-fail diagnosis. Reference datasets differ, and population averages may not reflect an individual’s health, training background, body composition or goals.
Relative VO₂ max is also affected by body mass because the result is divided by kilograms of body weight. A change in weight can therefore alter the relative value even when absolute oxygen use changes less. For tracking over time, the absolute and relative values, testing protocol, exercise performance and wider clinical picture should be considered together.
A low result can arise for many reasons, including inactivity, deconditioning, incomplete maximal effort, musculoskeletal limitation, medication effects or cardiovascular, respiratory, metabolic and muscular factors. VO₂ max alone cannot determine which explanation applies.
What this means in practice
VO₂ max testing provides personalised insight into your physiology that can help optimise training and monitor improvements in fitness over time. When respiratory and heart-rate responses are assessed across the test, the findings may help establish training intensities and more individual heart-rate zones.
Consistent aerobic activity, including walking, cycling, swimming, rowing, interval training and running, can meaningfully improve VO₂ max over time. The most appropriate approach depends on current fitness, health, preferences and goals. Regular moderate exercise can build a foundation, while appropriately prescribed higher-intensity intervals may provide an additional stimulus for some people.
Retesting under similar conditions can show whether cardiorespiratory fitness has changed. This is more informative than comparing isolated results obtained on different devices or with different protocols. It is also possible for meaningful improvements in thresholds, exercise economy or sustainable workload to occur even when VO₂ max changes only modestly.
When to seek professional advice
Maximal exercise testing is not appropriate for everyone without prior assessment. Medical review is particularly important if you have chest discomfort, unexplained breathlessness, fainting, palpitations, known cardiovascular or respiratory disease, significant cardiovascular risk factors, a recent illness or a major change in exercise tolerance. A health professional can determine whether testing is suitable, whether precautions are required and how the result should be interpreted.
The bottom line
VO₂ max is more than just a fitness score. It is one of the strongest indicators of long-term health that we can measure. The good news is that it can often be improved with appropriate training, making it a valuable health marker that you can actively influence. It should still be interpreted as part of a wider health picture, not as a diagnosis or a prediction of an individual lifespan.
How Executive Medicine can help
Executive Medicine’s Premium Plus assessment includes VO₂ max testing as part of a broader doctor-led health assessment. Results are considered alongside the exercise response and other relevant health information, helping translate the measurement into practical, individual guidance rather than treating it as a standalone score.
References
- Poole DC, Jones AM. Measurement of the maximum oxygen uptake V̇O₂max: V̇O₂peak is no longer acceptable. View source .
- Ross R, Blair SN, Arena R, et al. Importance of Assessing Cardiorespiratory Fitness in Clinical Practice: A Case for Fitness as a Clinical Vital Sign. View source .
- Mandsager K, Harb S, Cremer P, et al. Association of Cardiorespiratory Fitness With Long-term Mortality Among Adults Undergoing Exercise Treadmill Testing. View source .
- Molina-Garcia P, Notbohm HL, Schumann M, et al. Validity of Estimating the Maximal Oxygen Consumption by Consumer Wearables: A Systematic Review With Meta-analysis and Expert Statement. View source .
- Milanović Z, Sporiš G, Weston M. Effectiveness of High-Intensity Interval Training versus Continuous Endurance Training for VO₂max Improvements: A Systematic Review and Meta-Analysis of Controlled Trials. View source .
