Apple Watch Heart Rate Sensor Problems: Defective Hardware or Buggy Software

Shortly after I got my Apple Watch, I realized that its heart rate sensor was defective. I contacted Apple who had me perform a couple of resets, then the WatchOS 1.0.1 software update was released. I applied that update, and it did not improve matters. (Though for many users, that update broke the heart rate sensor.)

I got a replacement Apple Watch today, under the assumption by AppleCare that the device was faulty. I still see the same thing. Here’s a screenshot from the Health app, showing some problems:

Heart rate sensor problems

You can see one reading that’s way too high (162, at 12:24), and another that’s way too low (58, at 12:34). Note that all these readings were manual; I was walking on my treadmill, but I did not initiate a workout, in order to see if the Apple Watch would count any of this time as Exercise.

So, the question is this: are there a lot of defective Apple Watches, where the heart rate monitor doesn’t work? Since mine was faulty out of the box, before the 1.0.1 software update, this is possible. Or is it buggy software, which affected some users (such as me) from the get go, and is now affecting more users?

If you have an Apple Watch, I’d love to hear your experiences. It might help determine whether it’s a hardware or software problem; though it might be a combination of both. Perhaps the watch has difficulty reading the heart rate of certain people (even if they don’t have tattoos).

20 thoughts on “Apple Watch Heart Rate Sensor Problems: Defective Hardware or Buggy Software

  1. I’ve had my Apple Watch for about 10 days now and I use the fitness features practically every day. Before I got the watch I used a FitBit One, and a chest strap heart rate monitor for activities, such as an elliptical or strength training, that the FitBit didn’t handle well. I continued to use these other devices in combination with the Watch as a double check.

    As far as heart rate is concerned I find that the Watch checks pretty well with the heart rate monitor. Both have occasional brief excursions when they indicate a heart rate that clearly unreasonably low or unreasonably high, but both usually correct quickly. The excursions do not generally occur at the same moment so it is not that my heart rate is suddenly peaking or something like that. Over the course of a 60 minute workout these excursions don’t have much effect on overall accuracy. I may be mistaken but I believe a chest strap heart rate monitor is the gold standard for non-medical devices so if the Watch is doing as well as that I am satisfied.

    I do notice a different problem with the Watch’s fitness tracking. When I use it on the treadmill the distance it records is about half the distance the treadmill records. The Watch does fine on distance when I walk outdoors but then it has the iPhone’s GPS to rely on. I am aware I have to calibrate the Watch by walking outdoors and I have done that several times to no avail.

    Do you find the Watch accurate on distance on the treadmill?

    • No, like you, I find it it records about half the distance. This shouldn’t be the case, as I have calibrated the watch, and it knows the length of my stride.

  2. I’ve had my Apple Watch for about 10 days now and I use the fitness features practically every day. Before I got the watch I used a FitBit One, and a chest strap heart rate monitor for activities, such as an elliptical or strength training, that the FitBit didn’t handle well. I continued to use these other devices in combination with the Watch as a double check.

    As far as heart rate is concerned I find that the Watch checks pretty well with the heart rate monitor. Both have occasional brief excursions when they indicate a heart rate that clearly unreasonably low or unreasonably high, but both usually correct quickly. The excursions do not generally occur at the same moment so it is not that my heart rate is suddenly peaking or something like that. Over the course of a 60 minute workout these excursions don’t have much effect on overall accuracy. I may be mistaken but I believe a chest strap heart rate monitor is the gold standard for non-medical devices so if the Watch is doing as well as that I am satisfied.

    I do notice a different problem with the Watch’s fitness tracking. When I use it on the treadmill the distance it records is about half the distance the treadmill records. The Watch does fine on distance when I walk outdoors but then it has the iPhone’s GPS to rely on. I am aware I have to calibrate the Watch by walking outdoors and I have done that several times to no avail.

    Do you find the Watch accurate on distance on the treadmill?

    • No, like you, I find it it records about half the distance. This shouldn’t be the case, as I have calibrated the watch, and it knows the length of my stride.

  3. I think you are being a little unreasonable in your expectations. The watch is strapped to the back of your wrist and you are moving around. I don’t think it takes much to jar the watch loose while it is trying to take your pulse. From your image above, it looks like for both anomalies, the watch tried again to get a better reading. I’m not sure what else you want.

    I’m also curious if you are in workout mode when tracking your distance on the treadmill. I know in the past that you’ve complained that you shouldn’t have to enter workout mode but again, I think you are being unreasonable. Starting a workout puts you watch into a much more energy intensive mode that you wouldn’t want for normal use. It is a compromise for battery life.

    On the other hand, if you are in workout mode for indoor walking or running and the treadmill distance is inaccurate, that clearly seems to be a software issue.

    • All due respect, but I’m being unreasonable because the watch does not perform as advertised? I’d suggest you go to the Apple forum thread I link to and see how others feel about this.

      And, yes, when I do an indoor walk, it registers about half the distance of my treadmill walks.

      • You actually are being unreasonable. Apple never claimed the Watch records HR 100% accurately, 100% of the time and that seems to be what you’re expecting. Anomalies like this are inherent in even hospital HR monitors, and they get averaged out over time.

        • I agree. It certainly can’t be 100% correct. But it shouldn’t be reading, say, 150 bpm for a half hour, when my real heart rate is, say, 100. And it shouldn’t be reading, well, 50, when my heart rate is 100. Not just a single reading, but for a long time.

  4. I think you are being a little unreasonable in your expectations. The watch is strapped to the back of your wrist and you are moving around. I don’t think it takes much to jar the watch loose while it is trying to take your pulse. From your image above, it looks like for both anomalies, the watch tried again to get a better reading. I’m not sure what else you want.

    I’m also curious if you are in workout mode when tracking your distance on the treadmill. I know in the past that you’ve complained that you shouldn’t have to enter workout mode but again, I think you are being unreasonable. Starting a workout puts you watch into a much more energy intensive mode that you wouldn’t want for normal use. It is a compromise for battery life.

    On the other hand, if you are in workout mode for indoor walking or running and the treadmill distance is inaccurate, that clearly seems to be a software issue.

    • All due respect, but I’m being unreasonable because the watch does not perform as advertised? I’d suggest you go to the Apple forum thread I link to and see how others feel about this.

      And, yes, when I do an indoor walk, it registers about half the distance of my treadmill walks.

      • You actually are being unreasonable. Apple never claimed the Watch records HR 100% accurately, 100% of the time and that seems to be what you’re expecting. Anomalies like this are inherent in even hospital HR monitors, and they get averaged out over time.

        • I agree. It certainly can’t be 100% correct. But it shouldn’t be reading, say, 150 bpm for a half hour, when my real heart rate is, say, 100. And it shouldn’t be reading, well, 50, when my heart rate is 100. Not just a single reading, but for a long time.

  5. Oh dear, James… no, no, no…
    “…I think you are being a little unreasonable in your expectations…”

    It’s the other way around.

    Tis Apple, raising expectations unreasonably, methinks… (i just read the Shakespeare review below this entry!)

    Apple has been steadily losing whatever high ground it claimed during the (still ongoing) “it just works” phase. In fact, the front page of Apple.com currently claims it’s 3 best selling, mega-profit making devices all work “beautifully together”.
    It’s not true, they don’t. Apple, like life, ain’t like that. They don’t do all the things they claim to do. And when they don’t, one simply stops trying.

    All Kirk is pointing out is that this colossal tech company has without a doubt released an untested trinket to a mass of guinea pigs (sorry, Kirk… that’s you.) But I don’t blame you for trying.

  6. Oh dear, James… no, no, no…
    “…I think you are being a little unreasonable in your expectations…”

    It’s the other way around.

    Tis Apple, raising expectations unreasonably, methinks… (i just read the Shakespeare review below this entry!)

    Apple has been steadily losing whatever high ground it claimed during the (still ongoing) “it just works” phase. In fact, the front page of Apple.com currently claims it’s 3 best selling, mega-profit making devices all work “beautifully together”.
    It’s not true, they don’t. Apple, like life, ain’t like that. They don’t do all the things they claim to do. And when they don’t, one simply stops trying.

    All Kirk is pointing out is that this colossal tech company has without a doubt released an untested trinket to a mass of guinea pigs (sorry, Kirk… that’s you.) But I don’t blame you for trying.

  7. I have an implantable loop recorder that records my heart rate whenever it becomes irregular. It too shows spurious rates, high and low, every time it is recording. The doctor and the engineer have both said that the bad rates are caused by movement. This surprised me as the device is implanted in my chest and wired to me. I suspect that relative motion may be the source of your problem.

    I suspect that the primary problem lies in the software – the integration time, noise filtering, and continuity are extremely important in rendering accurate results.

    • It’s a different way of reading the heart rate. It uses lights, and a sensor which examines blood flow in capillaries. As such, it’s a pretty well proven technology for running and other activities. I suspect yours is a less sensitive system, using electrical impulses, as an EKG does. (At least that’s how I understand it from a Google search.)

  8. I have an implantable loop recorder that records my heart rate whenever it becomes irregular. It too shows spurious rates, high and low, every time it is recording. The doctor and the engineer have both said that the bad rates are caused by movement. This surprised me as the device is implanted in my chest and wired to me. I suspect that relative motion may be the source of your problem.

    I suspect that the primary problem lies in the software – the integration time, noise filtering, and continuity are extremely important in rendering accurate results.

    • It’s a different way of reading the heart rate. It uses lights, and a sensor which examines blood flow in capillaries. As such, it’s a pretty well proven technology for running and other activities. I suspect yours is a less sensitive system, using electrical impulses, as an EKG does. (At least that’s how I understand it from a Google search.)

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