As I reported on Saturday, Apple changed the way the heart rate sensor works on the Apple Watch, changing a technical document that describes the feature, changing the way this feature is described for the Apple Watch.
Apple updated a technical document about how the heart rate sensor works. They are no longer saying that the Apple Watch reads your heart rate every ten minutes; instead, they say this:
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.
Here’s how that technical document looked on May 9 (via the Wayback Machine):
It’s also worth noting that Apple’s French version of this document still talks about 10-minute readings.
If you bought the Apple Watch as a fitness tracker, you may have wanted it to record your heart rate regularly in order to present you with a somewhat reliable estimate of the number of calories you’ve burned. Many users posting to a thread on Apple’s forums are quite angry about; this feature was one of the main reasons they bought the watch. The Apple Watch, without this feature, is little more than a fancy step counter, unless you start a workout with the Workout app.
I find this to be a bit ridiculous. As I’ve written here before, either Apple realized that the heart rate monitor simply isn’t reliable (as I’ve seen), or they wanted to save battery life. If the latter was their rationale, they should have an option to allow the user to choose whether they want 10-minute readings. As one user on the Apple forum said:
“I absolutely do not trust my rings to be accurate at all. And if they are not accurate or consistent, how can you even use them to monitor progress? This thing is basically worthless as a fitness device. And that was the main reason I purchased it.”
While knowing your resting heart rate is useful, and is a good way of determining your cardiac fitness, you don’t need to do it every ten minutes when you’re not moving; in fact, that is simply foolish in terms of battery life. You do, however, need to record the heart rate when someone is walking, even if they’re not doing a workout, in order to have an idea how active they are. If someone is walking to work, they’re not going to bother to start a workout; and they shouldn’t. But their activity should be counted as more than just steps. For now, that doesn’t seem to be the case.
I think the problem is in the accuracy of the heart rate sensor. As Apple’s technical document explains, the Apple Watch has two types of heart rate sensors.
Apple Watch uses green LED lights paired with light‑sensitive photodiodes to detect the amount of blood flowing through your wrist at any given moment.
These sensors are used when you are in workout mode. But the device also has other sensors:
The heart rate sensor can also use infrared light. This mode is what Apple Watch uses when it measures your heart rate every 10 minutes.
While it’s a bit ridiculous that this part of the document still talks about 10-minute readings, what’s important to note is that these readings, which seem to be less accurate, are using a different sensor. It seems that Apple found these readings to be unreliable, and simply turned them off. (It’s worth noting that even with the 10-minute checks, I still had plenty of battery life at the end of the day, before the 1.0.1 update that turned off this feature.)
To many users, it looks like Apple pulled a bait-and-switch, promising a certain feature and not delivering it. Apple needs to say whether the change is because of faulty heart rate sensors – which means they have a bigger issue – or because of battery life. And if it’s the latter, they should allow users to choose whether or not the Apple Watch checks their heart rate every ten minutes. Let users decide how they want their battery usage to work.
However, if the heart rate sensors are faulty, simply turning them off, after promising this feature, is a mistake. They should fix them, whether through a software update, or by exchanging the devices. They promised a feature, and they can’t simply pretend that they never did so.
Note: one other interesting tidbit that an Apple forum poster pointed out, and that I confirmed on my iPhone’s Health app, is the fact that the Apple Watch doesn’t seem to be recording any heart rate readings below 61 bpm. I’ve had some much lower, which were incorrect, but a few around 57-59 which are probably correct. (Even though I’m not the fittest guy out there, my resting heart rate is fairly low.) Since the 1.0.1 update, I’m seeing that, every day, the lowest recorded heart rate is 61.