Heart Sensor

Discussion in 'Apple Watch' started by ryanpfw, Jul 5, 2016.

  1. ryanpfw macrumors member

    Jun 4, 2011
    Quick question about the heart rate sensor. I never tend to pay it much attention, but did note today when resting on the glance that I had a heart rate of 42. Concerned it was low, I checked my archive and found ten dates it trended low over the past 18 months.

    Leaving the glance on throughout the afternoon, it dropped into the 40s ten or so times, and with the glance remaining on jumped from 42 to a more reasonable number, 75, 85 directly. At one point after walking several feet, it calculated 50, then 112, then 88 in succession.

    I do have a physical coming up, but just for standard use, is it common to see such varying successive shifts in heart rate?
  2. Volusia macrumors 6502


    Jun 8, 2016
    Central Florida
    I am not a doctor, and I have not played one on TV (you have to be pretty old to understand that reference) but it sounds like your sensor is not getting a good reading. Unless you are a professional athlete or in incredibly good shape a heart rate (HR) of 42 sounds awfully low during waking hours.

    While I am not a doctor, I am a heart failure patient so I monitor my HR pretty regularly. If I get varying readings like you are describing I take my watch off and wipe down both my wrist and the back of the watch. This almost always fixes the problem and my readings come back into a more logical rhythm.

    This morning while doing a lot of yard work I checked my HR and got a reading of 52 BPM. I knew that wasn't correct, so I did my cleaning and got a reading of 88. I also use an app (HeartWatch) which alerts me when my HR goes over a preset rate, I got a notice from that program that my HR had exceeded my set limit a few minutes before I checked it, so it can happen fast.

    Edited to include: Your watch needs to be fitted correctly to your wrist also. For me, it is snug but not tight. I can not twist it but when I remove it there are no strap marks on my wrist.
  3. ryanpfw thread starter macrumors member

    Jun 4, 2011

    Thanks for responding! I did as you suggested and have received multiple successive readings in the 88-110ish range, with one spike to 122 after climbing the stairs. But I did receive one reading of 61 in between two readings in the 110s with no physical change. It suggests a bad reading.

    While obviously heart ailments can differ, should my bpm drop into the 40s, I would have expected the next immediate reading to also be low. I have yet to duplicate a very low reading, and wanted to check out the track record before requesting a battery of tests.
    --- Post Merged, Jul 5, 2016 ---
    • image.jpeg image.png image.png image.png image.png image.png image.png
    I am including some of the health data to highlight my concern. It seems there are readings that are anomalies, or shift wildly over five seconds. This is not a normal phenomenon?

    Attached Files:

  4. risenphoenixkai macrumors regular

    Oct 14, 2008
    The Watch's heart rate monitor is an optical sensor. Anything that constricts blood flow through the arm you're wearing it on will result in erroneous readings. This is why the Watch's built-in HRM isn't really well-suited for weight lifting or any other activity that potentially alters blood flow into the extremities.

    I have the opposite problem: my resting heart rate is usually in the mid-40s to low 50s (I work out a lot), but I'll occasionally get spiked readings in the high-60s to mid-80s, whether that's via the Glance or the automated 10-minute readings. I've been wearing and using the Watch long enough to know that it's not my heart rate itself that's all over the place, but minor errors in the measurements that are inherent to the type of sensor the Watch uses.

    Bottom line: it's probably nothing to do with your heart itself and therefore nothing to worry about. If you're really concerned, you can do one of two things:

    1. Get a Bluetooth HRM chest strap and pair it with the Watch. This type of HRM is far more accurate and has the added advantage of delivering constant, real-time results (the Watch's optical sensor only reads once every few seconds, even during workouts).

    2. See a cardiologist and get an EKG. That's a sure-fire way to be certain your heart is healthy (or not).
  5. Julien, Jul 6, 2016
    Last edited: Jul 6, 2016

    Julien macrumors G4


    Jun 30, 2007
    Obviously an anomaly since the :apple:Watch is taking 6 to 8 samples per minute. Your HR is not likely going from 77 to 44 to 77 in the span of a few seconds.

    Also as someone that has used HR monitors (chest strap Pulsar, Nike, Garmin,... and Apple) for well over a decade I can say that inaccurate readings happen fairly often. And as noted optical is generally less accurate than a strap. Remember the :apple:Watch is just a consumer device and NOT even close to a medical device. Take all readings 'with a grain of salt'.

    Just for kicks I tested mine and was able to get into the forties without much effort.:D

  6. Newtons Apple Suspended

    Newtons Apple

    Mar 12, 2014
    Jacksonville, Florida
    When in doubt find your pulse on your wrist of neck and count the beats for 15 seconds and multiply by 4 for your HR. My AW does the same, I have even see 24 for a heart rate while walking so it is just a erroneous reading.

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