Why do I have a different fitness age on Garmin compared to Mia?

Garmin uses American reference data to estimate VO2 max and fitness age, whereas Mia Health relies on research data from the HUNT study (The Nord-Trøndelag Health Study) conducted by NTNU. Unfortunately, We don’t have detailed knowledge of how Garmin calculates its estimates beyond this.

Your VO2 max and fitness age values are initially estimated using data from the HUNT study, where individuals with the same height, weight, gender, and training habits as you have undergone objective VO2 max tests. The answers you provided when creating your Mia Health account are compared to participants with similar characteristics in the study, forming the baseline for your estimated VO2 max and fitness age. From this starting point, both values are continuously adjusted based on your activity level, meaning the more data you sync with Mia Health, the more accurate your estimates become.

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