Optical HR reading 100 low during intensity?

I live in an area with a lot of steep, punchy hills that create the situation of going from Z2 to close to a sustained max HR. With both my Garmin Foreunner and Wahoo Tickr Fit (both optical sensors) I frequently run into the problem of my HR reading low when attacking these hills. Often, it’s in the 80 to 90 range, which makes me wonder if it’s reading 100bpm low, perhaps thinking that the quick jump to 190 is in error. Today, for example, while going all out up an 11 to 17% grade, the Wahoo read from the 80s to around 110 the entire time.

Anyone else experienced this problem?

All the time. Even with a Z2 ride indoors my Forerunner 935 will read 30~60bpm but the strap is of course right. If you want heart rate data buy a strap.


Well darn. Just spent $80 on the Tickr Fit replacing one I lost. Guess I’ll go back to the chest strap.

I have never had as much as 100bpm difference but every ride my watch (optical HR sensor) is lower than my strap but not by a constant amount. FWIW today’s ride the watch recorded 153 bpm and the strap recorded 188bpm.

Optical sensors away from the wrist are supposed to be more accurate but I have no experience of them.

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Some optical hr are less than ideal for bike rides…

Fwiw, i have a polar ohr and works great…

Yes, the Polar OH1 (new version now renamed “Verity Sense”) has none of these issues when worn on your upper arm. I find that way more comfortable and convenient than a chest strap and just as accurate.


Problem is you are using optical heart rate.

I have had absolute all out efforts where I should be 180+ register as 120, cause it never rose.

I have had super leisurely 120 style efforts register as 180, my cadence due to the shifting of the body I presume.

Not bad for low level steady state, but anything with varying efforts and higher intensity and they are worthless for many people.

Back to the strap for me, and been happy ever since.

I would agree entirely with this, but the Polar OH1 optical sensor is definitely an exception. But it’s not worn on the wrist. My max HR is around 190 and my OH1 never reads low. It’s always right on the money, while the optical sensor on my watch is massively inconsistent during HIIT sessions, often reading way too low.


If you’ve got to use optical, the OH1 seems to be one of the best:

But if you’ve got to have accuracy, then a standard strap would still be my move.

I have not tried the polar OH1 specifically but have used another arm band option, the scosche rhythm+ Hoping the arm placement would be an improvement, but no luck for me.

Perhaps polar has a more reliable hardware and firmware combination, or the stars have aligned for one to work just right for you lol :slight_smile:

OHR does tend to be less responsive than chest straps. Not a major issue for longer efforts, but can lag on short sharp efforts.

Also, vibration from handlebars can be an issue for wrist-based sensors when riding outside.

Are you recording a ride on the Forerunner, or just using 24/7 monitoring. You should record the ride, as the OHR sensor will poll more frequently during an activity than in 24/7 mode (you can discard rather than saving at the end to avoid duplicates).

Yes… They take a bit longer to register hr… but at the end is a wash… You will see higher hr a little later… Happens to me all the time on vO2 max efforts… The first 5 seconds on the rest the hr still climbing…

Optical works fine for me on the trainer, but no other time.

I think the Polar OH1 is just better than your average optical sensor. DC Rainmaker has always spoken highly of it. I have other optical wrist sensors that have the usual issues of reading low at high intensity.

Yeah. My Tickr Fit is a piece of junk. Both the original and the warranty replacement.

My Garmin OHR (Instinct Solar) is excellent. HOWEVER, you must be recording an activity even if you discard it at the end or it will significantly under read.

When I originally got it I had a number of emails to support toing and froing about the issue, being fobbed off with every excuse under the sun until I did a bit of testing for myself. So even if you tell the watch to “broadcast HR” it will still give a severe under-read unless you put it into recording activity mode. Then discard the activity afterwards.

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If you peek under the watch at the sensor, you will see why - while it is recording an activity, the sensor is solid on, rather than strobing.

Indeed. Bizarrely though, my old Forerunner 235 used to work perfectly well if you put it in broadcast mode without recording an activity. :man_shrugging:t4:

I just looked out of curiosity, the Fenix 6 does go solid in broadcast mode. Must just be certain models.

I just did too…and it goes solid. Unless they updated the issue in a software update :thinking:

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