This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

9.33/9.36 has ruined heart rate monitoring!


After upgrading my my fenix 7 to 9.33 I have noticed a few odd things about the heart rate that's displayed/recorded on my watch. Here's what I noticed:

First run with the new Firmware: My old H7 chest strap sensor, which worked fine before, showed sudden drops in HR of about 30 bpm while running at a constant pace. (H7 has a fresh battery.)

I thought was just the chest strap, but then I noticed sudden mayor changes in HR with the integrated HR sensor as well, when I was just at home. Within 2 seconds it jumped or dropped by about 20 bpm.

Also, when I stand up after sitting for a while, my heart rate does not change at all on the watch. It keeps showing mid to high 40s. However I can clearly feel that it's way off for about 15 to 20s and then it starts "catching up". > Again I big jump in HR on the watch. I tested this multiple times by comparing it to the data from my H7 + old watch where it behaved as expected – a gradual increase in HR.

I also restarted the watch which didn't help and I made sure I was wearing it correctly. (I wore it the same way before upgrading the firmware.)

Before the upgrade it felt very reliable and now I don't know what to think. Has anybody else noticed something similar? Any suggestions on what to do now?



  • If you choose to believe the Polar H10 is an industry standard, that is your choice. I personally do not have a preference across brands and you will find a million different opinions on OHR technology and HRM technology. The one thing that seems to be agreed across experts, you will always have the best results wearing a HRM strap. Whether our own or a 3rd party. However, that does not mean all HRM straps are made equal.

  • Former Member
    0 Former Member over 1 year ago in reply to Garmin - Chris

    Let's just leave that variable right off the table then (the HRM baking it's data), why would the readouts be different across Garmin devices? This advocates for a potential software issue on Garmin's side. Unless you are insinuating that HRM's are transmitting variable data dependent upon which device it is connected to. 

  • We have many generations of new OHR technology at this point. Going back to the Fenix 3 HR and forward.

    On the software side, I encourage those with OHR concerns to please reach out to Outdoor Product Support in your region. Thank you.

  • Thinking about this more, I believe most HR sensors transmit both plain rolling HR values and R-R vales, which are also called IBI (inter-beat intervals). R-R vales are raw and unprocessed but HR values are produced by applying some rolling averaging. Perhaps these two devices consume two different streams of data. But I know that Suunto certainly records R-R intervals - that is how it determines respiration rate. I think Garmin must be recording R-R intervals too in order to determine the respiration rate but I am not certain.

    I should add that today I repeated the same experiment while running, but it was a steady effort tempo run, so the difference between the two devices was minimal. So certainly, at least at a steady effort two two readings are in sync. 

  • Since you own a Forerunner 955, please post in the FR955 forum. The Forerunner is Fitness segment has a different engineer team and different software on the watch series. Thank you.

  • I updated to the latest beta and ever since my heart rate readings with hrm-run and hrm-dual have been all over the place, reading went sky high on an easy run, higher than my max HR ever has been, and then dropped drastically in steps of 5-10 beats at a time, nothing like I've ever seen before. Both chest straps are Garmin with new batteries.

    Thank you for your report. Please be sure to report your issue to engineering since they directly monitor and read all bug reports for those using Alpha or the Public Beta Software.

    Beta Program > Fenix 7 Series > Public Beta Reports

  • Could you please just make a thread about it on the bugs forum, so it could get upvoted and the engineers actually see it? Its pretty pointless for any of you to complain here.

  • I updated to the latest beta

    Thank you for your report. Please be sure to report your issue to engineering since they directly monitor and read all bug reports for those using Alpha or the Public Beta Software. (No one else worldwide using the Beta software has reported an issue using HRM straps. Your report will be critical since you will be able to clearly show your own issue with your activities HRM information.)

    Beta Program > Fenix 7 Series > Public Beta Reports

  • There's already a bug report in the beta 10.xx forum 

  • Here is a follow up for my previous post about running with Polar H10 HRM connected simultaneously to two watches - Garmin Fenix 7XSS and Suunto Ambit3 Peak.

    I managed to capture FIT files from both watches and overlay the HR graphs using website. As I mentioned in my previous post that run was a steady effort run and the HR values matched on both devices for the most part. However there is still a clear difference in the first 2 minutes of the run.

    The red graph here shows HR recorded by Suunto Ambit3 Peak while the purple one - the HR recorded by Garmin Fenix 7XSS.

    As you can see the Suunto graph goes up more sharply, which is more realistic considering I ran fairly fast from the beginning. The first few seconds I was still standing still, but then as I started running the Suunto HR graph took off more sharply while the Garmin HR graph went up much more gradually. 

    Again, the actual HR came from the same external sensor. If this isn't the software based smoothening, then I don't know how else this can be explained.