Heart Rate Showing As Half Of Actual

Discussion in 'Apple Watch' started by Gmouse, May 11, 2017.

  1. Gmouse macrumors regular

    Joined:
    Nov 12, 2014
    Location:
    Lakewood, CO
    #1
    For the last three weeks, when I go to my twice-weekly exercise session with a personal trainer, my watch has been reading 1/2 of actual (actual is 144, watch shows 72). Since my resting heart rate is ~75, I know after 20 min of exercising it is going to be much higher, and, usually the watch is pretty accurate compared to an actual heart monitor they have at the gym.

    Watch is at latest software version, I don't see any settings that would affect the reading. I have tried cleaning it (I usually clean it every month or so, just water and some mild soap using a microfiber cloth), cleaning my wrist, changing band (I have leather, sport, link), and I'm still getting the off readings.

    BUT...every once in a while...it seems to suddenly read right.

    Any thoughts? Do I need to take it in or get it replaced?

    Thanks
     
  2. risenphoenixkai macrumors regular

    Joined:
    Oct 14, 2008
    #2
    Any type of exercise you do that makes heavy use of your arms, such as weight lifting, is going to cause erroneous heart rate readings due to the type of monitoring tech the Apple Watch heart rate monitor (HRM) uses. Optically-based HRMs aren't going to provide accurate results any time blood flow to the extremities is constricted. Unfortunately, this means the built-in HRM won't work well at all for many types of workouts.

    Two bits of good news:

    1. There's nothing actually wrong with your Apple Watch at all. It's just limited by the kind of HRM it uses.
    2. You can get around the limitations of the built-in HRM by buying a chest strap HRM that syncs to the Watch via Bluetooth. I've been using a Polar H7 chest strap for over a year now, and it works like a charm.
     
  3. Relentless Power macrumors P6

    Relentless Power

    Joined:
    Jul 12, 2016
    #3
    I would agree. The Apple Watch heart rate sensor is nothing more than a general measurement. You will never have a completely accurate reading and even if you wanted a more steady reading, as you noted, you would want to invest in the heart rate chest strap.

    My other suggestion would be to help achieve a more stable reading with the Apple Watch, is to make sure that the Apple Watch is positioned correctly on the wrist and make sure the strap is snug, not being too tight or too loose.
     
  4. Gmouse thread starter macrumors regular

    Joined:
    Nov 12, 2014
    Location:
    Lakewood, CO
    #4
    Thanks, I understand that it's not the most accurate. My question is why is is measuring half of my actual heart rate? And, that just started about three weeks ago. Up to that time, it was at least seeming to measure close to what the clinical heart rate monitor was reading.
    --- Post Merged, May 11, 2017 ---
    Yep, I understand that it's not ever going to be the most accurate. And, some of the exercises I do are entirely with my lower torso, with my arm in the horizontal position, grasping on to a bar, so, it's fairly still. Yet, it's still reading off...by EXACTLY half. That's what concerns me, and makes me think something changed or is calculating wrong. Of course, I guess, the appearance of the blood movement that the sensors are reading COULD have changed, I guess, making the sensors only read half for some reason. I don't really think that's the case, as it seems to have a normal heart shape and rhythm when observed on the clinical heart rate meter. Thanks!
     
  5. Julien macrumors G3

    Julien

    Joined:
    Jun 30, 2007
    Location:
    Atlanta
    #5
    Have you tried re-paring? This would probably clear up any software related issue.
     
  6. pedrowerner macrumors regular

    pedrowerner

    Joined:
    Aug 24, 2016
    #6
    It happens to me when I'm working out and some sweat goes into the sensor, then it will read my blood but with some refraction from the water of my sweat and then it will read half of my actual heartbeat. Try cleaning your sensor with a dry cloth.
     
  7. Julien, May 13, 2017
    Last edited: May 13, 2017

    Julien macrumors G3

    Julien

    Joined:
    Jun 30, 2007
    Location:
    Atlanta
    #7
    Sweat can't get into the sensor. Also any sweat, moisture or water will have a very minimal impact (if any) since the infrared light passes through it. The infrared light is not absorbed or reflected and is a lot like the way you can see through sweat. In order to reach your red blood cells (this what absorbs the infrared) it must also passes through your skin, fat and muscle tissue (all of which contain a lot of water and are FAR more opaque than sweat).
     
  8. ManicMarc macrumors 6502

    Joined:
    Jul 1, 2012
    #8
    What model is it? The original sport watches had a plastic coating on the sensor, instead of ceramic. I've found mine is scratched where the charger attaches magnetically with some force. Worth checking. The 2016 Series 1 switched to ceramic so it's not an issue for these. I still get a good reading, though it's usually higher than my chest strap, but that's always been the case so I don't think it's anything to do with the scratches. Typically the if I go for a run with just the watch, my average heart rate is around 173, whereas with the chest strap it's about 155 - 169.
     
  9. pedrowerner macrumors regular

    pedrowerner

    Joined:
    Aug 24, 2016
    #9
    It's the series 2. I meant to say the sweat gets between the skin and the sensor, you're saying the IR light doesn't work like any other light according to physics? I didn't say reflection, actually it is refraction.
     
  10. bhayes444 macrumors 6502a

    Joined:
    Jul 13, 2013
    #10
    The series 1 watches still use the composite backs the original sport models used. The series 2 models all use the ceramic back.
     

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