I’ve found the blood oxygen feature on the Apple Watch to be worthless. The error bars on its measurements must be massive, so I would get numerous measurements every day down in the 80s. Better, finger-tip-based hardware measurements taken at the same time were never below 96%. And I’m careful about wearing the Watch just the way Apple recommends. I ended up just turning the feature off entirely, because I don’t want junk data in my Health history. I actually agree with Masimo’s CEO, who said, “I really feel wholeheartedly that consumers are better off without it."

No, V̇O2 max is estimated by the Apple Watch without any help from the blood oxygen sensor. I’ve had the blood oxygen sensor turned off on my Apple Watches for years, but I still get V̇O2 max estimations after outdoor runs.

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