Apple released the first software update for the Apple Watch on Tuesday, which fixed a collection of security problems and improved the sensor that can tell if you’re sitting or standing.
The Apple Watch originally measured the wearer’s heart rate every 10 minutes, and would work out an average heart rate from that data. You could measure it manually, too, but it quietly logged your heart rate all day long.
Now, those regular heart rate checks are gone, and the Apple Watch sporadically measures it during the day. It doesn’t look like that’s what Apple intended, and it appears that something in the latest software update broke the functionality.
Here’s how the Apple Watch used to measure heart rate. There were regular measurements every 10 minutes after putting it on:
And here’s how the heart rate measurements look after the update. Note the irregular measurements:
We reached out to Apple for this story and will update if we hear back.