Users of the Apple Watch who have noticed some unusual quirks in the heart rate monitoring tools now have an explanation, with Apple revealing that it's changed the beat-counting system in the 10.1 software upgrade so it -- intentionally -- doesn't update heart data while owners' wrists are moving. No jokes, please. It's serious business.
The update has been explained in detail on Apple's support pages, where the maker explains: "Apple Watch attempts to measure your heart rate every 10 minutes, but won't record it when you're in motion or your arm is moving. Apple Watch stores all your heart rate measurements in the Health app."
The change there is that it "attempts" to measure heart rate every ten minutes as before, but if there's too much motion going on it presumably now bails out rather than logging potentially wrong results.
Apple then goes on to explain all about photoplethysmography, the process by which its Watch attempts to measure our blood flow and heart rates. It warns that it might not work if your Watch is on too loose, if the weather's too cold or if you've spent way too much time on internet forums and have developed a thicker than usual skin. [9to5Mac]