Problem with heart rate monitor

Discussion in 'Apple Watch' started by vann, Jan 27, 2016.

  1. vann macrumors newbie


    Jan 27, 2016
    Nantes (France)
    Hello ;

    Sorry in advance for my English, it’s not my mother tongue. If I said something wrong, say it to me.

    I have an issue with the heart rate monitor of my watch sport. At least I think.

    Yesterday I got my first workout, not bodybuilding but step (I’m not sure if it’s the name in English, but this is when you “dance” on a step), plus a crossfit. Each one during one hour.

    And the bpm it show me was completely crasy. Somme time it says 58 bpm except that I was in the middle of my workout, and sometimes it says nothing, just it was trying to read my bpm.

    So I change the location of it on my forearm, up and down, tighten it or loosen it. No change.

    Do you think it’s the way I wear it ? or it’s my watch who has a problem?

    Thank you beforehand.
  2. Newtons Apple macrumors Core

    Newtons Apple

    Mar 12, 2014
    Jacksonville, Florida
    Just read the threads below, "Similar Threads" and you will see that you are not alone. The Apple Watch does not replace a good device that is dedicated to fitness.
  3. zhenya macrumors 603


    Jan 6, 2005
    All wrist-based HR monitors are subject to different factors that affect their accuracy. They must be worn tight enough on the wrist that no ambient light can get between your wrist and the sensor. They shouldn't have too much moisture there (sometimes removing the watch, wiping the sensor, then placing it back on the wrist tightly is enough). They don't work as well on dark-skinned individuals, or those with excessive dark hair on their arms. And even in the best of circumstances, the Apple Watch implementation is merely average at best.

    If you can't get a good reading no matter what you do, but you still want heart-rate data, the watch is compatible with 3rd party bluetooth chest straps which will likely be more accurate.
  4. Julien macrumors G4


    Jun 30, 2007
    You should be able to get an accurate reading while doing Zumba/Step. However doing any anaerobic (or highly mixed aerobic/anaerobic like CrossFit) activity will not be as accurate. When lifting weights the muscles constrict and mask vascular optical HR measurements. Also HR is not an accurate indicator of effort or caloric burn in anaerobic activities anyway.
  5. vann thread starter macrumors newbie


    Jan 27, 2016
    Nantes (France)
    Thank a lot for your answers. So I will purchase a chest strap (Wahoo Fitness TICKR seem very good).

    Fortunately the Apple Watch is compatible with this kind of devise.
  6. Raine132 macrumors newbie


    Feb 6, 2016
    An Apple associate once told me that the heart rate monitor will read half heart rate. So if your heart rate is 170 and Apple watch reads 85 it’s accurate. Not sure I like that.

    My issue is when I am on an elliptical workout. I used a polar heart rate strap that pairs with the machine, and compared it with the Apple Watch. While the strap monitor was fairly steady moving a few beats up or down as I sped up or slowed down, the Apple Watch readings were all over the place from 65 to 135 while my strap was reading between 105 and 110. Towards the end of my workout Apple Watch was reading close to the strap monitor but I don’t think I can trust it.

    Resting heart rate seems accurate. I will continue to check and I'll take the suggestions of some of the comments, like wearing it a little more snugly (althought it's comfortably snug now) and cleaning the underside. Hopefully I wil get a better reading. It doesn't have to be perfect, just near to accurate as a wrist monitor can get.
  7. b0fh666 macrumors 6502a


    Oct 12, 2012
    no way, if it was HR/2 i'd surely be dead doing workouts at 260 bpm :-D
  8. exxxviii macrumors 65816


    May 20, 2015
    That is probably bad information. I do not think it is consistent with most people's experience here.
  9. bjet767 macrumors 6502a

    Oct 2, 2010
    There is a huge difference in how the AW checks your HR verses a chest strap version, such as the Wahoo product. The AW essentially "looks" at the skin on your wrist for the pulse while the chest strap is measuring some sort of electrical change.

    Basically if you are moving around, have something blocking the wrist, or a even lots of hair the AW has a hard time "seeing" the pulse accurately. If your serious about fitness and measuring HR then get the chest strap.
  10. Raine132 macrumors newbie


    Feb 6, 2016
    Of course you wouldn't double a 130 heart rate but if the AW was reading 65 and you know you're working hard, I suspect he meant that's when you would double the number. Eventually the AW should show the 130 rate. But the only way to be sure is a heart rate monitor strap. Not terribly convenient, nor comfortable but if you want accuracy I guess for now that's the way to go.
  11. bjet767 macrumors 6502a

    Oct 2, 2010
    I find the AW is OK in measuring HR if one stands still and makes sure it it is pressed against one's skin. And it doesn't show 1/2 heart rate, that's just a salesman who is making something up.
  12. BlueMoon63 macrumors 68020

    Mar 30, 2015
    I can run for an hour with the Apple Watch and get perfect readings almost every time I have used it. He worst case scenario has been losing the pulse 5-6 times in an hour. I have used a borrowed Fitbit and now my daughters Fitbit HR and they are essentially the same though the Fitbit rarely loses a pulse. When I lose the pulse on the Apple Watch, it drops to 58 for a minute or two before bouncing back.

    I noticed the best success wearing the watch tighter and 1 to 1 1/2 hunches up my wrist like the Apple ads show. Cold weather was worse unless I started out indoors to get my body tempt up. Fitbit never failed.

    I ran for an hour today on my treadmill and never lost a reading. Same for yesterday on my elliptical. I must be lucky.
  13. bjet767 macrumors 6502a

    Oct 2, 2010
    "I noticed the best success wearing the watch tighter and 1 to 1 1/2 hunches up my wrist like the Apple ads show. Cold weather was worse unless I started out indoors to get my body tempt up. Fitbit never failed. "

    You nailed the whole issue, it has to be tight.

    From the Apple Support Page:

    "You can check your heart rate any time using the Heart Rate Glance. And when you're using the Workout app, Apple Watch measures your heart rate continuously during the workout. This information, as well as other data it collects, helps Apple Watch estimate how many calories you’ve burned. In addition, 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 heart rate sensor in Apple Watch uses what is known as photoplethysmography. This technology, while difficult to pronounce, is based on a very simple fact: Blood is red because it reflects red light and absorbs green light. 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."

    "If your Apple Watch doesn’t stay in place, or the sensors aren’t reading your heart rate, tighten the band a bit."

    "Many factors can affect the performance of the Apple Watch heart rate sensor. Skin perfusion is one. A fancy way of describing how much blood flows through your skin, skin perfusion varies significantly from person to person and can also be impacted by the environment. If you’re exercising in the cold, for example, the skin perfusion in your wrist may be too low for the heart rate sensor to get a reading.

    Motion is another factor that can affect the heart rate sensor. Rhythmic movements, such as running or cycling, give better results compared to irregular movements, like tennis or boxing.

    Permanent or temporary changes to your skin, such as some tattoos, can also impact heart rate sensor performance. The ink, pattern, and saturation of some tattoos can block light from the sensor, making it difficult to get reliable readings.

    If you’re not able to get a consistent reading because of any of these factors, you can connect your Apple Watch wirelessly to external heart rate monitors such as Bluetooth chest straps."

    Right from the horse's mouth, the AW uses light to measure the HR and if it can't see the movement then it can't read the HR.
  14. OTACORB macrumors 65816


    Jun 21, 2009
    Central, Louisiana
    I've had this issue myself recently and it is rather frustrating. I generally walk daily and cycle and one thing I found is that on days when it really humid (most days here in the south) my watch will drop out and give me sporadic readings. One particular day I was cycling several miles and was sweating and the watch even quit tracking my mileage. I had to stop, wipe the sweat from my wrist area, wipe off the back of the watch and it immediately picked up my HR. I have started wearing the watch a bit higher on my arm and tighter by a notch, so its been working much better. Still not totally fool proof, but better. I thought about buying a strap, but that just wouldn't be convenient. While tracking my activity is important if its off a tad here and there, it's not REALLY that big of a deal.

    I have been on Fitbit forums and Garmin forums and this seems to be an issue across all these watches from what I've read as I thought about ditching my Apple watch for one of these others, but now I've decided to keep rocking with the Apple Watch.
  15. Raine132 macrumors newbie


    Feb 6, 2016
    I've been monitoring my heart rate with a strap that links with my and the gym's elipitcal machines. I moved the watch up my wrist a bit and made it slightely tighter. Now the heartrate monitor and Apple Watch are almost perfectly in sync. So I think it's safe to say that if worn correctly and follow some of the points in this thread, the AW can be trusted to be close to accurate.

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