Adam James.

VO2 Max: What The Hell Is It?

What is VO2 Max?

VO2 Max (also maximal oxygen consumption, maximal oxygen uptake, peak oxygen uptake or maximal aerobic capacity) is the maximum rate of oxygen consumption measured during incremental exercise (exercise of increasing intensity).

The name is derived from V – volume, O2 – oxygen, max – maximum. Maximal oxygen consumption reflects the overall cardiorespiratory fitness of an individual. It is an excellent way to assess an individual’s fitness level.

While it is true that the VO2 Max test can help determine endurance capacity during prolonged exercise, there’s a common misconception that only trained runners, cyclists and endurance athletes can benefit from the test.

Is VO2 Max only important for athletes & secret agents?

The short answer is no. VO2 max is widely used as an indicator of health. In 2016, the American Heart Association published a scientific statement recommending that cardiorespiratory fitness (CRF), quantifiable as VO2 max, be regularly assessed and utilized as a clinical vital sign. This statement was based on mounting evidence that lower fitness levels are associated with high risk of cardiovascular disease, all-cause mortality, and mortality rates stemming from various types of cancers. In addition to risk assessment, the AHA recommendation cited the value measuring fitness for validating exercise prescription, physical activity counselling, and improving both patient management and patient health.

Conversely, good fitness level significantly reduces your likelihood of developing chronic illness. For both moderately active individuals and athletes, VO2max assessment is vital for training and performance. 

How is VO2 Max measured?


VO2 max is properly defined by the Fick equation:

VO2 Max Health Fitness Weight Loss
Source: Deranged Physiology, an online resource for Intensive Care Medicine. learn more.

Accurately measuring VO2 max involves a physical effort sufficient in duration and intensity to fully tax the aerobic energy system. In general clinical and athletic testing, this usually involves a graded exercise test (either on a treadmill or on a cycle ergometer) in which exercise intensity is progressively increased while measuring:

  • ventilation and

  • oxygen and carbon dioxide concentration of the inhaled and exhaled air.

VO2 max is reached when oxygen consumption remains at a steady state despite an increase in workload.

How does Apple Health calculate VO2max?

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.

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


A smart watch at best is predicting your VO2 Max.  It definitely shouldn’t replace a lab test.  However, it is a useful indicator of an individual’s approximate fitness level.



I'm a musician, a podcaster, a blogger & I work in marketing. I live in Australia and have two dogs named Ned & Sasha.


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