I use Garmin edge 520 with Garmin dual heart rate monitor and it shows completely false results like maximum hr >180 and average hr 150, while my ride is easy, slow and flat and I don't feel any discomfort. Measuring my hr with my finger I get much lower indications. Probably this happens because of an (controled) arrhythmia that I have. How to overcome the faulty results of my hrm? Is there any monitor or system that may be more acurate? Thank you in advance!

  • 3
    Do you know that these numbers are wrong? How do you take the reference measurement?
    – ojs
    Commented Jun 14, 2021 at 11:55
  • 1
    This is a common problem, and there are several possible causes. Poor skin contact is one possibility, but this can also be due to a medical condition that makes the heart rate hard to read. Commented Jun 14, 2021 at 12:01
  • I never had much luck with chest strap models, especially out on a bike (as opposed to in the gym, mostly on a treadmill). Some people find the LED-based upper arm ones better, but they tend to be more expensive. I only borrowed one once briefly; it worked but that wasn't enough of a test to recommend either way
    – Chris H
    Commented Jun 14, 2021 at 12:25
  • I had to try different HRM to find one that has reliable results for my physiology. (In that case a Sigma HRM). Others I tried measured either nothing or garbage.
    – gschenk
    Commented Jun 14, 2021 at 12:31
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    Ask your GP or heart specialist about the correlation of the readings and your condition. Fingertip readings and IR trans-skin devices are not the most reliable, especially vs. chest straps. (One thought, is your GPS software up to date?)
    – Carel
    Commented Jun 14, 2021 at 15:51

4 Answers 4

  1. Try replacing the battery, it could be running flat.
  2. Make sure you're getting proper contact with your HRM to your chest - try adding some conductive gel.
  3. Try a different soft strap, they wear out after a while.

I've had inconsistent readings from all 3 of the above issues at times.

  • Taking the battery out for 2 minutes, un-pairing the strap from your GPS and repeating the pairing procedure after having replaced the battery as your 4th possibility.
    – Carel
    Commented Jun 14, 2021 at 15:44

As mentioned already, one likely problem is poor contact.

One easy way to test for poor contact is to get the contact area wet - and I mean wet.

Put on your HRM strap and get your GPS unit. Turn on the GPS unit, and when it's reading your HR - or when it should be reading your HR - take a full water bottle and soak in between the HRM strap and your skin. Get it really wet.

Now see how your HR is reading. If the reading improves and starts to reflect what you get if you measure your pulse by other methods, you have problems with your HRM because of bad contact. You might have to wiggle your strap around a bit, or wet it more than once and wiggle it around a bit.

If this doesn't result in improved accuracy, it doesn't really mean anything - you could still have contact issues.

If you don't want to get your floor wet, do this outside or while standing in a shower or tub.

  • 1
    Chemist's (drug-stores) sell conductive gels of the kind doctors use for ECG. You may also wet the patches on the strap with salt water.
    – Carel
    Commented Jun 14, 2021 at 14:56
  • 3
    I never found tap water (or saliva) very effective, and often had to get a good sweat on to make reliable contact
    – Chris H
    Commented Jun 14, 2021 at 15:09
  • The use of oil-based skincare lotions & creams may also be an obstacle to good conductivity. The instructions with my strap recommend soaping the strap every five uses to remove oily residues from the skin. A GP friend of mine told me once that there are people whose skin gives unreliable ECG readings.
    – Carel
    Commented Jun 14, 2021 at 15:39

Since no-one else mentioned it - this can be caused by the air causing some synthetic shirts/base layers to flap/flutter.

I had a top that got relegated to use on the indoor trainer because when wearing it outdoors my HRM would record 200+ any time I picked up any speed.

  • Interesting, I can confirm that this is a thing, at least with older generations of Garmin straps (the current HRM Pros don't show such anomaly). I wasn't fully sure if it is a flapping shirt interfering or the circumstance that an opened or thin jersey exposes the sensor to wind and drying up the sweaty/wet skin surface it depends on for reliable readings.
    – DoNuT
    Commented Feb 29 at 6:28

After trying the suggestions from other answers, consider that the numbers might be real. I do have the same problem and I returned my first HRM because I thought it was faulty. It turned out that I just do have unusually high heart rate without any known heart conditions, so that 150 is more or less normal for casual riding and the maximum is somewhere beyond 200. The "220-age" formula is not really true or even a good approximation.

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