This Is What Happens When an Apple Watch’s Heart Rate Sensor Doesn’t Work Correctly

A few days ago, I wrote about how the Apple Watch may not be very accurate as a fitness tracker. Many of the issues I’ve encountered are widespread, and many users have reported similar problems. Seemingly ridiculous calorie calculations, the exercise ring not recording exercise, and more.

Apple issued an update to the Apple Watch software a couple of days ago, which seems to have fixed some of these issues, for some users. In my case, the watch is still screwy.

After contacting Apple’s technical support, and doing a number of things to try and determine if this was a software problem – applying the 1.0.1 update, and resetting the watch – it’s clear that this is, indeed, a problem with the heart rate sensor. Apple will be exchanging the watch.

Here’s the kind of thing I was seeing. In the first example above, I was walking outdoors in the evening, with the Workout app recording my walk as a workout. You can see that my heart rate jumped from 111 at 20:32 to 150 a few seconds later. My pulse was not that high; this was simply that the watch was recording it incorrectly.

In the second example, to the left, from another evening walk, my heart rate was around 112-113, then it jumped to 122, before dipping to the low 80s. Again, my pulse was stable.

I’ve also seen examples where the watch simply stopped recording my heart rate for one to three hours: the Health app data shows that there are no readings for a long time.

So, if you’re having issues with the Activity app, check what heart rate has been recorded. To do this, go to the Health app on your iPhone, tap Health Data, then Vitals. Tap Heart Rate, and then Show All Data. You’ll see every reading that your watch has recorded. You can check to see how reliable it is.

One thing I have noticed is that if I have the Heartbeat glance active, the watch forces a reading when I switch to it, and that reading is usually accurate, and tends to somehow force the automatic readings to be correct again. So, if I see that my heart rate, when walking, is around 150, I switch to the Heartbeat glance, and the new reading seems to reset the sensor to the correct values.