[francisofascii]

> There were big swings in my resting heart rate whenever I got a new Apple Watch, suggesting the devices may not have been tracking the same way.

First of all, wrist based HR measurements are not reliable. If you feed ChatGPT a ton of HR data that is just plain wrong, expect a bad result. Everyone who wants to track HR reliably should invest in a chest strap. The VO2 Max calculation is heavily based on your pace at a given heart rate. It makes some generalizations on on your running biomechanics. For example, if your "real" lab tested VO2 max stays constant, but you improve your biomechanics / running efficiency, you can run faster at the same effort, and your Apple watch will increase your VO2 Max number.

[AlanYx]

In this case the article's guess is probably accurate. Apple did change how they measure RHR in WatchOS 11.2. If the author was using an Apple Watch that doesn't support 11.2 and then switched to one that does, a swing was very likely.