The VO₂ Accuracy of Wearables | Peter Attia

The gist

1. Wearables estimate VO₂ max from heart rate, pace, and demographics rather than measuring gas exchange directly, so the numbers are inherently imprecise.
2. Wrist optical heart rate sensors can be off by 5 to 10 percent or more, which compounds the error in any downstream VO₂ max calculation.
3. A reading of 52 on a wearable could reflect a true VO₂ max anywhere from 42 to 62, making it too imprecise for serious fitness planning.
4. Attia says heavy zone 2 training can cause wearables to underestimate VO₂ max automatically, without the user having any control over when estimates are generated.