Garmin Forerunner users - heart rate accuracy?

by Daveyraveygravey   August 12, 2014  

I recently posted about a max speed anomaly I noticed, descending Titsey Hill - It looks like I got up to 109 mph, but the explanation about tree cover blocking the satellite for a bit and the software then interpreting the gap with a sudden bit of speed makes sense.

With heart rate, I see blips now and then, which don't make a lot of sense to me. I usually get up early in the morning and go out on rides, and when I first switch on my hr is around 90. Often within the first 10 minutes it will drop to 50/60, and I have seen it as low as 37 one time. Conversely, my max is usually 170-180, but sometimes it will spike to 220 or so. Both these cases are short term and my HR will then settle to my usual range of 90-170, and I have set my training zones to that.

On Ridelondon at the weekend, I pushed myself and got round in 4 mins 18. Because of the weather I didn't pay much attention to my Garmin, especially after the half way point by which time the rain had made it difficult to see the screen, and it was dangerous to be taking both hands off the bars to wipe it and then look at it. It seems I averaged 164 over the course with a max of 179.

If I'm willing to ignore the highs and lows as short term blips, how much faith should I put in one long ride at what seems unbelievable? My suffer score on Strava is rated as extreme at 407. My next few rides will be very gentle z1 or 2, I don't feel like I have done myself any damage but am concerned all the same.

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If you got round RideLondon in 4mins 18s then I think you should expect a high pulse Big Grin
But seriously....
I have read any number of posts (mainly on running forums) about weird pulse rates on various makes of pulse meter. A lot are Garmin based, but Garmin is a popular make...
On my Garmin 301 when the battery in the strap 'goes' it just stops reading the pulse. However I have noticed that when my 310 (Ant+) strap 'goes' the pulse seems to read higher than I would expect. Try changing the battery?
I do not think that the heart rate meter in a Garmin is sophisticated enough to diagnose a heart problem! See your Dr if you are concerned, if your weird pulse rate is accompanied with symptoms, chest pain, dizziness, a 'fluttering' feeling in the chest etc consider 999!
The problem being of course that if you are worried about your pulse reading then you will probably get chest pain, dizziness, a 'fluttering' feeling in the chest etc just worrying about it Worried
Your Dr is the person to talk to, an ECG is an easy procedure along with a discussion on various risk factors if you are concerned. Let me/us know how you get on.

posted by SideBurn [913 posts]
12th August 2014 - 10:20

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posted by Bliss moments [2 posts]
12th August 2014 - 17:40

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The older Garmin HRMs can be very unreliable. The newer one I got with my FR620 has been faultless both running and used with my Edge 800.

davecochrane's picture

posted by davecochrane [130 posts]
13th August 2014 - 11:52

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The HR strap doesn't always work as well as it might.

Really, though?

posted by workhard [393 posts]
13th August 2014 - 13:09

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Thanks all. I usually position it just under my nipples, is that right?

I changed the battery recently, I'd seen it stop registering my HR so knew it was that.

Interesting there is no reference to the strangely low reading after starting out from everyone else, maybe it's something my heart does?

posted by Daveyraveygravey [311 posts]
13th August 2014 - 13:12

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The first HRM I had was from Aldi and regularly recorded maximums in excess of 210 bpm. As I was 65 years old at the time this was a worry!

Crosshouses's picture

posted by Crosshouses [271 posts]
13th August 2014 - 13:26

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I used my Garmin HRM yesterday at the gym and compared it to the one on the bike. I was never further than about 5bpm out and usually within that. Far as I'm concerned, that's probably in the noise and nothing to be overly worried about.

ride slow, ride far, ride often

posted by mzungu [41 posts]
13th August 2014 - 16:12

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Daveyraveygravey wrote:
Thanks all. I usually position it just under my nipples, is that right?

Under the moobs. Don't forget to wet the contacts or it'll be inaccurate until you start sweating

ride slow, ride far, ride often

posted by mzungu [41 posts]
13th August 2014 - 16:13


This is a common complaint, and varies from person to person, as your skin ultimately determines the performance of the strap. If it bothers you there are various electrode creams you can buy to improve the accuracy, but it hardly seems worth it unless you have very, very dry skin.

posted by giobox [358 posts]
14th August 2014 - 1:01

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I have the deluxe HRM that came with my Garmin Edge 500 and it appears to be quite accurate with none of the highs and lows you describe. It is true you need to wet it (or use an electrolyte cream as stated above). As for positioning I have the strap around the bottom of my ribcage with the sensor in the centre just below the bottom of my sternum. Hopefully this helps. The data readings you are getting are hopefully a glitch and not a serious health issue but it might be worth speaking to your doctor just to be on the safe side

posted by Kauto [23 posts]
14th August 2014 - 12:01