PROBABILITY DU JOUR
The VO2 max estimate on the Apple Watch (indirect methods) is imprecise.
But no need for direct methods.
The AW has a high person-specific bias, but a low variance.
This means that the CHANGES in VO2 max you observe over time (what matters) are quite precise.
https://nitter.moomoo.me/nntaleb/status/1651939270066683906#m