Body Insights turns your selected VO₂ max into a Fitness Age in whole years. It also shows how that result differs from your actual age. You can use Cardio Fitness stored in Apple Health. Or you can choose the app's calculated VO₂ max, which comes from your maximum and resting heart rates.
Fitness Age is a focused comparison of aerobic fitness. A younger result means your VO₂ max matches the reference value for a younger adult. Use the six-month trend to see whether the direction holds. One workout or one difficult week cannot show that.
What goes into the Fitness Age calculation?
Three inputs build the current result:
- Your selected VO₂ max source
- Your current age
- The female or male reference curve for your biological sex
Choose either Apple Health Cardio Fitness or Body Insights calculated VO₂ max. The calculated option uses your maximum and resting heart rates to estimate VO₂ max.
Current Fitness Age
VO₂ max sourceYour selected Apple Health or Body Insights value
Also usesCurrent age and reference curve
Six-month history
VO₂ max sourceApple Health Cardio Fitness only
Also usesCurrent age and reference curve
Body Insights uses the selected source for the current result. Its history chart always uses Apple Health Cardio Fitness. This means the current number and older months can come from different sources.
How does VO₂ max become Fitness Age?
VO₂ max is the amount of oxygen your body can use during hard exercise. A higher value usually maps to a younger point on the reference curve. A lower value maps to an older point.
- Body Insights reads the VO₂ max source you selected.
- It compares that value with the female or male reference curve for your age.
- It shows Fitness Age in whole years and the difference from your actual age.
The result stays between ages 18 and 99. It also stays within 20 years of your actual age. These bounds stop one unusual value from producing an extreme age.
The reference pattern comes from the HUNT 3 Fitness Study. Researchers measured cardiorespiratory values in 4,631 healthy women and men aged 20 to 90. Body Insights uses the age and sex pattern from that reference data.
How can you use the six-month trend?
Open Fitness Age to see your current result and its difference from your actual age. The same view shows the six-month history and Improvement. It also shows Fitness Level, age-group ranking, and Contributing Factors.
- Compare several weeks or months to see whether the direction holds.
- Check your selected VO₂ max source before you compare the current result with earlier months.
- Use Fitness Age beside recovery, energy, symptoms, or daily capacity when they affect your plan.
A source switch can move the current result. It will not rewrite older months because the history stays tied to Apple Health Cardio Fitness.
When is Fitness Age available?
The current result needs your age, a usable VO₂ max, and a reference curve. Apple Watch can add Cardio Fitness during an Outdoor Walk, Outdoor Run, or Hiking workout. Apple says the first estimate can take at least 24 hours of watch wear. You will also need several supported workouts and passive measurements. See Apple's Cardio Fitness guide for the current device and workout details.
You can also choose Body Insights calculated VO₂ max. The app needs valid maximum and resting heart rates for that option. This source can produce the current result, but it does not fill the six-month history.
If biological sex is not set to female or male, Body Insights uses female reference values and tells you. Add your biological sex in the profile to use the matching curve.
Track your Fitness Age
See your current Fitness Age, the difference from your actual age, and six months of Apple Health history.
See my Fitness Age