Heart Rate Measured but no chest monitor and fenix 5 on handlebars

I've owned Fenix 5x for several years now using regularly for hiking, recently started biking and purchased Edge, Radar, Cadence and Speed sensors... mounted Watch and Edge on handlebars to compare when using radar....did 20 miles on bike and really liked the radar unit....but found that my HR was reported in 1 sec intervals for the complete ride. I do not remember wearing a HR Chest Strap and the Watch was mounted on handlebars....I am now concerned about validity of data from Fenix 5X or Garmin Connect....I do own a HR chest strap but was kicking myself for not wearing it when I got off my bike....could be old age....is there a way to check the source of HR measurements in Garmin Connect

Garmin Connect October 12th.pdf

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  • You can try uploading the fit file to www.fitfileviewer.com

    Under device_info will be listed all the sensors used.  Unfortunately numbers are used rather than names so it will take a bit of detective work to figure them out.  If you do 2 activities - one with the HR strap and one without you will be able to see the difference in the files and get your answer.

    In my case the wrist HRM is device type 10 and my HRM Run is device type 120

  • Thanks Ronand...was able to look up the sensors per your recommendation....took a long time to decipher all sensors I used but good learning experience...data shows the HRM data being recorded for 20 mile activity yesterday did not include the HRM Run Chest Strap; HR data derived from Fenix 5X wrist monitor strapped to a plastic support on the handlebars.  Considering bicycle doesn't share my pulse, most concerning find is plausible data (a.k.a. HR increases/decreases with climbs/cadence) and within a reasonable range based on effort....making me wonder how much plausible data vs accurate HR data I've been collecting and targeting over the last several years. Appreciate the great guidance!

  • Optical HRM accuracy is pretty dismal on any device once the heart rate is elevated to any degree. Its reasonably ok for walking but nothing any more strenuous than that.   If you want accuracy just use the chest strap.

  • This has been reported several times on other watches and the results can look quite realistic too. I’ve seen it from a 945 and Fenix 6. Easy to speculate what might cause this to happen but hard to prove. Vibrations perhaps? Similar has been seen when watch is placed back facing down on some surfaces.  


    if you wear a strap most of the time then most of the data will be good data. Of course best way to avoid this phantom data is to connect a chest strap when the watch is on the handlebars.