Fenix 5 optical HR vs HRM chest strap

My heart rate readings during running are consistently much higher using the optical sensor on my new Fenix 5, the they are when I use my HRM chest strap with my 920xt.
I have even ran with my 920xt and chest strap, while also having the Fenix 5 optical on the opposite hand. Everything seems similar, except the heart rate. My HR recording is a much higher number on the Fenix 5.

I bought the Fenix 5 to get rid of the chest strap. Do I just run and know/understand that the optical isn't a true number and disregard the readings?

Or do you typically just subtract after your run?

What do most people do in this case?

Does Garmin have a typical "rule of thumb" of how far off the optical is from the HRM chest strap?

Thanks!
Drew

0 Dr Phil over 8 years ago

..or do you spend a little time reading the plethora of posts about this very subject, wherein answers to your questions will be found. And BTW, this is not peculiar to the F5. Every device has the same issues with optical HR.

0 mcalista over 8 years ago

The normal cause of poor OHR accuracy is poor positioning and placement of the watch, allowing the watch to move on your wrist, excess light to entering the OHR sensor in a rythmic manner, and the watch to lock onto your cadence rather than your HR.

The watch band should be pretty snug and positioned on the fleshy part of your wrist well away from your wrist bone.

0 Crispin_Ellisdon over 8 years ago

There's no specifics from Garmin over how much less accurate a wrist OHR measurement will be than a chest strap but some general acceptance of the limitations of WHR in these links:
http://www.garmin.com/en-US/legal/atdisclaimer
https://support.garmin.com/faqSearch/en-GB/faq/content/A28UA4k16v1qjjGuvSFgo8
https://support.garmin.com/faqSearch/en-GB/faq/content/xQwjQjzUew4BF1GYcusE59

Switching to another big name in this game, there is some quite specific (and refreshingly honest) stuff from Suunto on the matter here http://www.suunto.com/en-GB/Content-pages/what-should-you-know-about-wrist-heart-rate/ So expect WHR to be within 5% of a chest strap for 90% of the time according to Suunto. They also acknowledge that activities with rapidly changing intensity or arm/wrist movement are not so well suited to the use of WHR.

Fellrnr has started some detailed comparative testing of OHR http://fellrnr.com/wiki/Optical_Heart_Rate_Monitoring that pretty confirms what we all knew about OHR already. If you're concerned about accuracy and precision, then there isn't an OHR on the market that can match a chest strap.

0 chunkywizard over 8 years ago

fellrnr is up to his old tricks again, like reusing the same track for all his measurements on GPS accuracy. He is using only one person (himself) for all the measurements. OHR works differently for everyone, I would suggest everyone sees how accurate the technology is for themselves rather than go on what he says.

0 Crispin_Ellisdon over 8 years ago

Agreed that one should treat Fellrnr's, or any individual tester's, findings with the respective caution it deserves. What is more interesting to me is the honesty shown in Suunto's website with regards WHR; I've always thought being honest and managing expectation up front is the best way to treat customers.