VO2 max, which stands for Volume of Oxygen maximum, is a measure of how much oxygen your body can use during intense exercise. It is expressed in milliliters of oxygen used in one minute per kilogram of body weight (mL/kg/min).
In simple terms, V02 max is a measure of how efficient you are at using oxygen, which correlates well to your overall fitness level.
As a metric, VO2 max is a predictor of aerobic fitness and performance capacity, so long as it is measured correctly. Generally speaking, a higher V02 max will correlate to better ability to preform endurance activities or cardio training. There are however limitations on what you can do to improve V02 max as it can be linked to genetics and body type.
The expected VO2 max varies depending on age, sex, and fitness level. For example, a healthy young adult male might have a VO2 max of 50 mL/kg/min, while a healthy older adult female might have a VO2 max of 40 mL/kg/min and still be in otherwise better overall shape.
Elite endurance athletes can have VO2 maxes of up to 80 mL/kg/min. Still many testing methods will not estimate extremely high or low V02 max simply because the accuracy is poor. For example the Apple Watch does not estimate V02 max above 60.
These ranges are fairly normalized and are reiterated by wearables and fitness apps that track V02 max, including the Health Mates App and it’s fitness level, as well as Apple Health cardio Fitness. We have previously covered the accuracy of various V02 max scores:
- HealthMate Fitness Score – An estimate of V02 Max
- Apple Watch V02 Max Accuracy estimates compared to Treadmill lab tests
VO2 max can be improved through regular exercise. Anyone following a marathon training plan or cycling training plan and using a wearable may notice changes in their V02 max. The most effective for improving VO2 max is aerobic exercise, such as running, swimming, or cycling. Aerobic exercise helps to increase the size and efficiency of your heart and lungs, which allows you to use oxygen more efficiently during exercise.
Cyclists tend to have higher relative V02 max compared to other athletes due largely to the body type makeup that benefits cyclists (ie. larger weight distribution in major muscle groups of the legs compared to runners or swimmers). Unfortunately the Apple Watch will not estimate a VO2 max from a cycling activity, it will only do so when doing an outdoor walk or outdoor run (of at least 20 minutes). Other cycling apps DO estimate VO2 max, including Zwift which will make an estimate based on hard efforts.
You can also improve V02 maximum readings simply by losing weight. Since the measurement of V02 max is “per unit kilogram” it is directly related to weight. All else being equal, losing 10% of your body weight will improve V02 max by 11.1%. These are not equal because losing weight will change the denominator in the calculation (ie. 1/100% is actually 11.1% more than 1/90%).
It is important to call out that improved V02 max does not directly impact these things, instead it is correlated. Simply having a higher V02 max than another person does not mean you will have better sleep or energy levels.
As with many health and wellness metrics it is difficult to say that maximizing V02 max on it’s own is the end objective. For example, a runner looking to improve their 5k time may want to increase their V02 max. While they can do this by losing weight, the weight loss will have impact on their 5k time because it takes them less energy to propel themselves forward.
As with anything it is worth considering that correlation (ie. having a high V02 max is common among elite athletes) is not causation (ie. having a high V02 max will make you an elite athlete).
How to Measure Your VO2 Max
There are a number of ways to measure VO2 max. The most accurate way is to use a treadmill or cycle ergometer in a laboratory setting. These tests will hook you up to a breathing device that directly measures the amount of C02 and O2 that you exhale. Since our bodies use 02 to produce ATP in our cells, with a byproduct being C02, measuring the output of C02 in your breath can estimate how much 02 is being used.
When these tests are done at a high enough intensity level, we can deem them to be measuring the maximum amount of 02 available. Since all of this is linked to the cardio vascular system, including the volume of blood pumped and the rate at which it is pumped (heart rate), there are also algorithms to estiamate V02 simply based on resting heart rate.
This means that there are both are also a number of field tests that can be used to estimate VO2 max based on sub maximal efforts, as well as even more simplified estimates that can be done just using resting heart rate.
Many of these field tests can be recreated by wearable devices that use estimates from cardio based training to estimate V02 max. These methods can be simplified into three categories:
- Lab test(DexaFit, Physical Therapist, etc.): The gold standard for measuring VO2 max is a lab test. This test involves running on a treadmill or cycling on a stationary bike while your breathing and heart rate are monitored. Med spas, health centers, high end gyms, and personal trainers all may conduct these tests. Each requires a testing apparatus that costs a few thousand dollars, a treadmill or exercise bike, and some computer software. PNOE is one of the primary makers of V02 max machines.
- Field test: There are a number of field tests that can be used to estimate VO2 max. These tests typically involve running or cycling for a certain distance or time. Wearables like the Apple Watch, Garmin Smart Watches, and Pixel or Fitbit smart watches all estimate these.
- How hard of an activity do you have to do to get a V02 max reading? According to Apple they make a prediction on sub-maximal efforts which means “an approximate increase of 30 percent of the range from resting heart rate to max“. With a resting HR of 50 BPM, and a max of 182, this means that even an activity that gets HR to 90 BPM will be capable of producing a V02 max result. Apple does not release the exact equation used to calculate V02 max, which implies that it is a simple regression model or prediction model based on a variety of inputs.
- Online calculator: There are a number of online calculators that can be used to estimate VO2 max based on your age, sex, weight, and fitness level. For the most part these calculators simply ask you to input resting heart rate along with the other noted age/sex/weight and it will spit out a V02 max estimate.
It is important to note that these are just estimates and your actual VO2 max may be higher or lower than the estimate. If you are interested in getting an accurate measurement of your VO2 max, you should see a doctor or certified personal trainer.
What is a Good V02 Max?
Since V02 max can be influenced by so many factors and itself is not an outcome many people optimize for, the definition of a “good” score must be better defined.
In studies for even high level athletes there have been known differences depending on the specialty of the athlete. For example, one study looking at just elite runners noted variations between sprinters with a VO2 max of 57.3, compared 61.7 for distance runners (3000M up to marathon).
This is an 8% increase even within athletes who are comparatively at the same level of competition. Just look at the body type of a 100M athlete though and you will quickly see that they are carrying significantly more muscle and weight in order to drive explosiveness over a short distance. Distance runners on the other hand benefit from being leaner since it reduces the amount of work they have to do to propel themselves over 3KM or more. See the study on V02 max in elite athletes here.
Similarly there are differences in V02 max depending on gender as well. Again this links to the physiology of an average male, who by default has less body fat, than an equivalent female as well as other similar comparisons.
A separate study from 2003 highlighted the impact of many variables on V02 max. It also called out that age, gender, BMI, and activity levels were valid predictors collectively of V02 max. In addition the method of testing also had an impact of the measured V02 max, which again highlights that the estimates from many wearable devices may not be entirely the best if looking for precision compared to a lab test.