VO2 max is often called the gold standard of aerobic fitness because it measures how efficiently your body can use oxygen during exercise, which is a key factor in endurance performance.1Habibi, E., Dehghan, H., Moghiseh, M., & Hasanzadeh, A. (2014). Study of the relationship between the aerobic capacity (VO2 max) and the rating of perceived exertion based on the measurement of heart beat in the metal industries Esfahan. Journal of Education and Health Promotion, 3(55), 55. https://doi.org/10.4103/2277-9531.134751
A higher VO2 max generally means you can sustain faster paces for longer, making it a valuable metric for athletes looking to improve their training and racing.
The challenge? While most runners and athletes have heard of VO2 max, few understand how to measure it outside of a lab or, more importantly, how to apply it to their own training.
In this guide, we’ll break down exactly what VO2 max is, why it’s useful, and the most practical ways to measure it—whether through lab testing, field-based methods, or wearable devices.
What Is VO2 Max?
VO2 max, also known as maximal oxygen uptake, is a metric that quantifies your aerobic capacity.
It refers to the maximum amount of oxygen (milliliters of oxygen in volume) your body can use per minute per kilogram of body weight while performing intense exercise such as high-intensity interval training (HIIT).
Your VO2 max quantifies the maximum rate at which you can take in oxygen, transport it to your muscles, extract it from the blood, and use it efficiently for aerobic energy production.
The higher your VO2 max, the more oxygen you can effectively use during high-intensity exercise through your cardiorespiratory system.
A high VO2 max theoretically enables you to produce more ATP (adenosine triphosphate) per minute, so your muscles can do more “work” or support faster running or higher-intensity exercise before crossing into your anaerobic threshold.
How Do You Measure VO2 Max?
The only reliable method for measuring VO2 max is in a laboratory setting using a metabolic cart and specific protocols developed for this purpose. Alternatively, you can estimate VO2 max based on various protocols that use heart rate.
Graded Exercise Test
The gold standard for measuring VO2 max is performing a VO2 max test in an exercise physiology laboratory or some clinical setting.
There are different lab testing protocols, but generally, you will walk or run on a treadmill or use a cycle ergometer.
Each of the VO2 max protocols has various stages that become increasingly difficult over time.
While performing the VO2 max test, you wear a specialized face mask hooked up to a metabolic cart.
This metabolic cart analyzes the composition of your expired respiratory gasses and compares the exhaled air to the percentage of gasses in the inhaled atmospheric air. This allows for a detailed evaluation of how much oxygen you consume versus how much carbon dioxide you exhale.
The relative proportion of these gasses is called the respiratory exchange ratio, or RER. Based on your RER, exercise physiologists can determine the relative percentage of each fuel source you burn: carbohydrates vs fats.
The closer the RER gets to 1.0, the higher the relative percentage of carbs you are burning, which means that you are hitting your maximum effort. An RER closer to 0.7 indicates that you are burning primarily fat for fuel and have not reached your VO2 max.
Note that at maximum-intensity exercise, your body relies almost solely on blood sugar and stored glycogen to fuel ATP production rather than body fat or circulating triglycerides.
The metabolic cart can also calculate the volume of oxygen you consume by measuring the amount of air you inhale. Because VO2 max measures oxygen consumption per minute per kilogram of body weight, this is a key factor in the VO2 max measurement protocol.
Simultaneously, your heart rate is recorded and used to indicate when you are likely reaching your maximum aerobic capacity.
Various VO2 max test termination criteria indicate if you’ve reached your true VO2 max.
How to Measure VO2 Max Outside of a Lab
Various field tests outside of a lab can estimate VO2 max.
Examples of VO2 max estimation protocols include the Rockport Walk Test, the 1.5-Mile Test, the Cooper VO2 Max Test, the Bruce Treadmill Test, the YMCA Cycle Ergometer Test, step tests, among others.
Let’s look at a few of these:
#1: VO2 Max Running Test (Field Test)
There are field tests to measure VO2 max, such as the 1.5 Mile Run.
This specific method of measuring VO2 max is a true max effort test, and it has only been validated for college-aged populations.
After running 1.5 miles on level ground as fast as possible, the time is converted into a decimal and then inserted into a VO2 max equation for this VO2 max measurement test as follows:
- Males: VO2max (ml/kg/min) = 88.02 + 3.716 – (0.0753 x body weight in pounds) – (2.767 x time for 1.5 miles in minutes and fractions of minutes)
- Females: VO2max (ml/kg/min) = 88.02 + – (0.0753 x body weight in pounds) – (2.767 x time for 1.5 miles in minutes and fractions of minutes)
Accuracy of Prediction. This test has a R = 0.90 and an SEE = 2.8 ml/kg/min
#2: Bruce Treadmill Test
The Bruce protocol2Sarma, S., & Levine, B. D. (2016). Beyond the Bruce Protocol. Cardiology Clinics, 34(4), 603–608. https://doi.org/10.1016/j.ccl.2016.06.009 treadmill test is one of several tests that can be used to assess cardiovascular health and fitness by estimating VO2 max.
‘This is a submaximal VO2 max values test, which means that your VO2 max will be predicted based on the trend in your heart rate at various workloads at a lower exercise intensity.
An equation and specific protocol have been created and validated. The data will extrapolate your estimated maximum aerobic capacity if you exercise at maximum intensity for a true VO2 max test.
This is essentially how any VO2 max measurement that doesn’t require maximal effort exercise works:
A protocol and algorithm/equation have been designed with decent accuracy and reliability for predicting V02 max based on the linear increase in heart rate at different stages of aerobic workload.
Because the percentage of max heart rate is strongly associated with the percentage of VO2 max, your heart rate data can, in an incremental exercise test, be used to estimate your VO2 max.
The Bruce protocol is a progressive treadmill test, which involves walking on a treadmill for three minutes per stage and progressing through specific established stages that get progressively harder.
This test protocol stops when the individual’s heart rate reaches 85% of its age-predicted maximum or exceeds 115 bpm for two stages.
After completing the test, calculations are performed using a formula that takes into consideration your sex and the total time that you lasted while performing the Bruce treadmill test.
Here are the formulas:
- Men: VO2 max = 14.8 – (1.379 x T) + (0.451 x T²) – (0.012 x T³)
- Women: VO2 max = 4.38 x T – 3.9
T represents the total time on the treadmill and is written as a fraction of minutes and seconds. For example, a total time of 8 minutes and 45 seconds would be written as T = 8.75.
For example, if a woman did the Bruce Protocol stress test and lasted 8 minutes and 45 seconds, this would result in the following VO2 max:
VO2 max = 4.38 x 8.75 – 3.9 = 34.425 ml/kg/min.
#3: The Rockport Walking Test
The Rockport Walking Test is one of the most popular submaximal VO2 max tests that predicts your maximum aerobic capacity based on walking 1 mile at an even pace; jogging is not allowed. The test has been validated on subjects between the ages of 30 and 69.
The key to improving accuracy with this VO2 max estimation protocol is taking the heart rate immediately after finishing the mile without waiting more than a couple of seconds at most.
Then, count the pulse for 15 seconds and multiply by four to get your heart rate in beats per minute.
Convert your fastest mile walking time into a decimal, so 14:30 would be 14.5.
VO2max calculations are then done by using the formula:
- Males: VO2max (ml/kg/min) = 132.853 – (0.0769 x weight in pounds) – (0.3877 x age) + 6.315 – (3.2649 x mile walk time) – (0.1565 x ending heart rate)
- Females: VO2max (ml/kg/min) = 132.853 – (0.0769 x weight in pounds) – (0.3877 x age) – (3.2649 x mile walk time) – (0.1565 x ending heart rate)
Based on research, there is a correction factor for individuals between 18 and 24 years old: You subtract 6 ml/kg/min from the value obtained from the regular VO2 max equation above.
Accuracy of Prediction. This equation has an R= 0.88.
#4: The YMCA Submaximal Bicycle Test
The YMCA Submaximal Bicycle Test is a popular submaximal test for VO2 max. You ride a stationary bike ergometer, following a specific resistance protocol and a cadence of 50 rpm.
You perform a couple of stages of exercise (3 minutes per stage) to obtain two heart rates between 110 bpm and 150 bpm to estimate VO2 max. A graph plots the heart rate at different workloads with a line of best fit inserted.
Then, this line is extrapolated up to your age-predicted maximum heart rate to estimate V02 max.
There are even non-exercise assessments that can predict V02 max based on your answers to questions regarding your physical activity, along with other demographics.
An example is the Jackson Non-Exercise VO2 max predictor.
As can be surmised, any submaximal or predictive way to measure VO2 max is not a true VO2 max measurement and will have a margin of error.
Accuracy of Prediction. This test has R= 0.86, SEE= 10% of the predicted VO2 max.
How Does The Apple Watch Measure VO2 Max?
As the utility and interest in measuring VO2 max for competitive and recreational runners, cyclists, triathletes, and everyday athletes have increased, some of the best fitness trackers, watches, and GPS running watches have started implementing a VO2 max feature so that you can estimate it on your watch.
For example, the VO2 max Apple Watch feature allows you to see an estimate based on your workout history.
It is calculated by evaluating the relationship between your pace and heart rate. An algorithm evaluates how fast you can run at various percentages of your age-predicted max heart rate.
The faster you can run at a relatively lower percentage of your heart rate, the higher your Apple Watch VO2 max score will be.
However, the Apple Watch VO2 max is determined based on submaximal exercise intensities, so it is a prediction of your VO2 max rather than a true measurement of your fitness level.
In addition to the Apple Watch capabilities, some of the premium GPS running smartwatches also offer V02 max estimations, including some Garmin and Polar models.
To learn more about how to improve your VO2 max with specific workouts to add to your training program, check out the following guide:
