How does Apple Health calculate VO2max?

In this brief article, we will answer the question of  “How does Apple Health calculate VO2 max?” and provide you with more tips on the benefits of knowing VO2 max and how to work towards improving it.

How does Apple calculate VO2 max?

Your Apple Watch automatically tracks your VO2 max over time and updates it to the Apple Health app on your iPhone. The Apple Watch takes a measurement of your VO2max every time you complete an outdoor walk, run, or hike that lasts longer than 20 minutes, using the Workout app.

If you want to get a more accurate measurement of your VO2 max, start with performing a gentle warm-up, then open the “Workout” app on your watch and select outdoor walk or run. Go for at least 20 minutes at a steady pace and, once you finish, there’ll be a new VO2 max reading.

What is VO2 max?

VO2 max is the max amount of oxygen you can breathe in from the air into your lungs. The oxygen is then transported by your bloodstream to your muscles, where it is converted into energy during a workout. 

The “max” in VO2 max means the measurement has to be taken when you are working out at the maximum level of exertion —essentially when it feels like giving it all you have got. VO2 max is the maximum volume of oxygen you can breathe in, that your body can utilize to generate energy.

It is measured in ml/kg.min. It is a metric that measures the volume of oxygen your body can utilize for every kg of body mass per minute. Dividing by the body mass averages the fact that a person with more mass will utilize more oxygen.

What is the benefit of knowing VO2 max?

Olympic cross-country skiers, competitive distance runners, racing cyclists and extreme fitness athletes are known to have a high VO2 max. VO2 max is basically a measure of cardiovascular or aerobic fitness. 

 It’s widely considered to be a strong indicator of your overall physical health as well as a factor in your long-term health outcomes.

VO2 max is widely used as an indicator of cardiorespiratory fitness. In 2016, a study by the American Heart Association published a statement recommending “that cardiorespiratory fitness (CRF), quantifiable as VO2 max, be regularly assessed and used as a clinical vital sign”. 

 How VO2 max is measured?

In the lab, VO2 is measured by hooking the test subject to various sensors and a respiratory tube that carries the oxygen into and out of the test subject. The test subject is made to undergo high-intensity interval training in which, different levels of exercise intensities are maintained so that VO2 max can be accurately analysed. By putting an oxygen mask over the subject during the test, the volume of oxygen input and output is measured, which in turn can be used to calculate the VO2 max. Apart from this, the heart rate and heart rate variation is also analysed during the test.

How is VO2 max different from Blood Oxygen Levels?

Blood Oxygen Saturation is a percentage of oxygenated blood to the total of oxygenated and deoxygenated blood in the body. It is a percentage value, whereas, VO2 max is a measure of oxygen volume consumed. The VO2 max is measured under physical stress whereas oxygen saturation has no restrictions to be measured under physical stress.

How does a smartwatch measure VO2 max?

In lab studies, there has been a correlation found between Maximum Heart Rate and VO2 max. The relationship between heart rate and VO2 max is not precise, and it may vary from one individual to another. The following equation is used commonly used

This forms the basis of the measurement behind VO2 max measurement in the Apple Watch. So Apple’s predicted VO2 max may not be very accurate. Although it is not a replacement for the lab obtained reading, it is a pretty good estimate.

How to improve your VO2 max?

The key to having a good VO2max is by being good at endurance sports. This is because endurance sports maintain a high intensity of effort for a long period of time. 

Running a few metres is good fun, but that is not going to train you for a marathon.

The reason you cannot keep up the fastest pace while running is because your body uses different energy systems to fuel different levels of workout intensity.

To be able to carry out high-intensity interval training you need a system that relies more on the aerobic energy system, this is where increasing your VO2 max comes in handy. 

To train your VO2 max, you need to engage in a workout of sufficient intensity that makes you reach your anaerobic threshold. This is the point where you feel out of breath. At this point, you can no longer sustain your workout with just your aerobic energy system. You will know when you approach the threshold, as you will get a burning sensation in your muscles along with shortness of breath.

Logging a 20-minute, high-intensity outdoor run workout once a week will help to increase your VO2 max. It will also ensure you regularly log your predicted VO2 max.


In this brief article we answered the question of  “How does Apple Health calculate VO2 max?” and provided you with more tips on the benefits of knowing VO2 max and how to work towards improving it.


Leave a Comment