Learn → VO2 Max
What is VO2 Max?
VO2 Max is the maximum amount of oxygen your body can use during intense exercise, in millilitres per kilogram of body weight per minute. It is the clearest single measure of aerobic fitness.
Why it is worth caring about
Beyond athletic performance, cardiorespiratory fitness is among the strongest measured correlates of long-term health outcomes in the epidemiological literature — comparable to, and in several large studies stronger than, conventional risk factors like smoking status or hypertension.
There is also a day-to-day consequence people underrate. A low VO2 Max means ordinary activity — stairs, carrying shopping, a brisk walk — sits at a higher percentage of your ceiling. Everything costs more, so tiredness becomes the baseline state rather than an event.
How your watch estimates it
A laboratory VO2 Max test involves a mask, a treadmill and exercising to exhaustion. Apple Watch instead estimates it from the relationship between your heart rate and your pace during brisk outdoor walks, runs and hikes.
That estimate is decent for tracking your own trend and less reliable as an absolute figure. It also needs qualifying activity to update — which is why readings often arrive every few days rather than daily, and why Biomon plots the real readings you have rather than filling gaps with invented ones.
The one thing you can genuinely change
Unlike age or genetics, VO2 Max responds to training — often substantially, and at any age. Two approaches do most of the work:
Zone 2 volume
Steady, conversational-pace cardio — you can talk in full sentences but would rather not. Unglamorous, and it builds the aerobic base most people are actually missing. Time spent matters more than intensity here.
Higher-intensity intervals
Shorter, harder efforts with recovery between. More time-efficient, more demanding to recover from, and best layered on top of a base rather than used instead of one.
Most programmes that work use both: a majority of easy volume, a small amount of hard work. The common failure is doing everything at a moderate middle intensity — too hard to build a base, too easy to drive adaptation.
On "fitness age"
Many apps convert VO2 Max into a "fitness age" or "biological age". It is a vivid framing, and it rests on a linear approximation of population decline that gets progressively less accurate the further you sit from the middle of the range — precisely where a dramatic number would be quoted.
Biomon shows your actual VO2 Max, its real trend, and how it compares to your age group, rather than converting it into a headline number the underlying model cannot really support.
Related
Body battery →
The day-to-day signal, next to this long-term one.
HRV →
Whether you have recovered enough to train again.
Sleep debt →
The recovery that training adaptation depends on.
This is general wellness information, not medical advice. Biomon is not a medical device and nothing here is a diagnosis. If something about your health concerns you, talk to a doctor.