VO2max testing measures how much oxygen your body can take in and use during strenuous exercise. The test itself does not make you fitter, but the information can help some people understand their current cardiorespiratory fitness, plan training and track changes over time.

VO2max testing is not essential for most people who want to become more active. For many adults, gradually increasing regular physical activity and following Australian exercise guidelines are more important than obtaining a laboratory-style fitness measurement.

This article provides general information only. It is not medical advice, does not diagnose heart or lung disease and is not a recommendation that any person undergo maximal exercise testing.

What Is VO2max?

VO2max, or maximal oxygen uptake, is the highest rate at which the body can take in and use oxygen during progressively harder exercise. It is commonly reported in millilitres of oxygen per kilogram of body weight per minute (ml/kg/min).

VO2max is one measure of cardiorespiratory fitness. It reflects the combined ability of the lungs, heart, blood and working muscles to deliver and use oxygen during exercise.

Cardiorespiratory fitness is associated with long-term health outcomes. In a large observational study of adults completing treadmill testing, higher fitness was associated with substantially lower mortality risk during follow-up. An association does not prove that a particular increase in VO2max causes a specific reduction in mortality risk, but the findings are consistent with the broader evidence that cardiorespiratory fitness is an important health marker.

Read the JAMA Network Open study.

Who Might Consider a VO2max Test?

VO2max testing may be useful for some people who want more detailed exercise data, including:

• endurance athletes who want laboratory or metabolic data to complement their training plan
• people preparing for endurance events who want a baseline measurement
• people following a structured exercise programme who want to compare results using the same testing method over time.

It is not necessary for most people who simply want to improve their general fitness. Australian physical activity guidelines can be followed without first measuring VO2max.

A fitness-focused VO2max test should also not be confused with a diagnostic test for heart or lung disease. If you have chest pain, unexplained breathlessness, fainting or other concerning symptoms during exercise, speak with your GP. A clinician may recommend a medically supervised exercise assessment or other investigation depending on your circumstances.

What Happens During a VO2max Test?

1. Pre-exercise screening

A responsible testing process should begin with questions about your health, exercise history, medicines and any symptoms. Australian exercise professionals may use the Australian Adult Pre-Exercise Screening System (APSS) to identify people who may need medical advice or clearance before strenuous exercise.

See the AUSactive Adult Pre-Exercise Screening System.

2. Gas analysis and monitoring

You typically exercise while wearing a mask or mouthpiece connected to a metabolic or gas-analysis system. The equipment measures gases in your breathing, including oxygen and carbon dioxide. Heart rate is commonly monitored at the same time.

3. Progressive exercise

The test is usually performed on a treadmill or stationary bicycle. Workload increases progressively until you reach a maximal or near-maximal effort, or until the test is stopped for another reason. The exercise phase is demanding, but the exact duration and protocol vary between testing facilities and individuals.

You should be able to tell the tester if you feel unable to continue. A properly supervised test can be stopped when necessary.

4. Results

The report may include VO2max, peak heart rate and other exercise measurements. Some testing services also estimate training-intensity or heart-rate zones.

These numbers are useful only when interpreted in context. Age, sex, body weight, exercise mode, training status, health conditions and the testing protocol can all influence the result.

Limitations to Understand

• Maximum effort matters. A test that does not reach a sufficiently high effort may underestimate maximal capacity.
• Testing method matters. Results from treadmill and cycling protocols are not directly interchangeable, so comparisons are more meaningful when the same method and protocol are used.
• Reference values vary. Normative values differ according to the population, testing equipment and protocol used. Ask which reference population is being used.
• Body weight affects relative VO2max. Because the common measure is expressed per kilogram, a change in body weight can affect the reported number even if absolute oxygen uptake changes little.
• It is one fitness measure, not the whole picture. Strength, movement quality, training consistency, recovery and day-to-day function also matter.
• It may not be necessary. Many people can improve their fitness without knowing their VO2max.

How to Prepare

The testing facility should give you specific preparation instructions because protocols differ. Common instructions may include:

• avoid unusually hard exercise before the test
• arrive normally hydrated unless you have been given different medical instructions
• avoid a large meal shortly before testing
• wear comfortable exercise clothing and appropriate footwear
• get your usual amount of sleep the night before
• tell the tester about current medicines, recent illness, injury and any symptoms you experience with exercise.

Do not stop or alter prescribed medicines simply to change a test result. Ask your doctor or the testing provider whether any medication requires special instructions before testing.

Safety and Possible Short-Term Effects

Maximal exercise is demanding. Temporary effects can include heavy breathing, a rapid heart rate, fatigue, sweating, muscle discomfort and, in some people, brief light-headedness or nausea after strenuous exercise.

Pre-exercise screening is intended to identify people who may have a higher risk of an adverse event during exercise. It is a safety process, not a guarantee that a test is risk-free.

Stop exercising and tell the tester immediately if you develop chest pain or pressure, severe or unusual breathlessness, fainting, significant dizziness, new palpitations or pain that spreads to the arm, neck or jaw.

What Can Influence VO2max?

Age

VO2max generally declines with age, although the rate of change differs between individuals and regular physical activity can help maintain cardiorespiratory fitness.

Sex and body composition

Population averages are generally higher in men than women, with differences influenced by factors including body composition, haemoglobin, heart size and muscle mass. Individual results vary substantially within each group.

Genetics

Inherited factors contribute to differences in baseline VO2max and in how much an individual’s fitness changes in response to training.

Training

Regular aerobic training can improve cardiorespiratory fitness. The amount of improvement varies with starting fitness, training type, frequency, intensity, recovery and individual response.

Health conditions

Conditions affecting the heart, lungs, blood or muscles can influence exercise capacity and VO2max. Anaemia, for example, can reduce oxygen-carrying capacity. Asthma and cardiovascular disease can also affect exercise performance.

Altitude

Higher altitude reduces the amount of oxygen available in the air and can affect exercise performance. The body can adapt over time, but results obtained at different altitudes are not necessarily directly comparable.

How to Improve Aerobic Fitness

For most people, the practical way to improve cardiorespiratory fitness is consistent aerobic activity combined with an appropriate progression in training.

Useful activities include brisk walking, cycling, swimming, running and other forms of aerobic exercise that suit your ability and circumstances. Higher-intensity intervals can form part of a programme for some people, but they are not essential for everyone.

Start at a manageable level and increase duration or intensity gradually. Adequate recovery is also part of training. People who are new to vigorous exercise or who have a medical condition should seek appropriate advice before starting high-intensity training.

See the Australian physical activity and exercise guidelines.

Is VO2max the Same as Fitness?

Not completely. VO2max is a useful measure of cardiorespiratory capacity, but fitness is broader. Strength, balance, mobility, muscular endurance, physical activity habits and the ability to perform everyday or sport-specific tasks are also relevant.

A person does not need an elite VO2max value to be healthy, and a single test cannot capture every aspect of health or exercise performance.

What to Look For in a Testing Service

If you are considering a VO2max test, ask who performs the test, what pre-exercise screening is used, what equipment and protocol are used, how results will be interpreted and what happens if you develop symptoms during testing.

It is also reasonable to ask whether the test is being presented as a fitness measurement or as a medical assessment. A fitness test should not be marketed as a substitute for diagnosis or treatment of a medical condition.