Any advice on heart rate inaccuracy

Lots of advice about the wrist heart rate throughout the posts for this device and others with WHR. Well worth spending a little time reading them. Pretty certain all your questions will be answered. If not, please come back and let us know if you are experiencing anything different.

What firmware are you using, 5.40? 5.30 is known to have some issues ith OHR.

thanks 5.4 but only for the last week. This morning's terribly inaccurate walk was with 5.4.

Lots of advice about the wrist heart rate throughout the posts for this device and others with WHR. Well worth spending a little time reading them. Pretty certain all your questions will be answered. If not, please come back and let us know if you are experiencing anything different.

I did do a whole lot of searching a week or two ago, and didn't find any solutions. One problem I had with the forums here is that it wasn't clear to me whether or not the posts for previous Garmins, especially for older ones, would be relevant.

I did another search, just to double check, and found your comment

https://forums.garmin.com/forum/into-sports/running/forerunner-235-aa/150659-?p=1072449#post1072449

"It sucks! ...unless you are doing relatively low intensity activities that do not affect the 'seal' between the sensors and the skin beneath"

If this is indeed the state-of-the-art view on the wrist optical heart rate on the forerunner, then I simply need to decide whether to return it to where I bought it, or accept the limitation and carry on using the device. It's just a shame that a good chunk of the "added-value" functionality, the training load recovery time estimates etc, are based on heart rate. And in particular on heart rate variability. When I did the research on the web it seemed, for example, that the Scosche RHYTHM+ would be a good alternative to a chest strap, but it doesn't provide HRV data so I'd lose some of the 935 functionality (which is pretty nice when I have a week's worth of good data, e.g. from using a chest strap).

I would recommend doing a hard/factory reset on the watch first. I had all sorts of issues with the recent updates until I did that. It sucks, but it did fix the problem.

Generally speaking, the 935 OHR has been outstanding for me, in every aspect. I used a Scosche Rhythm+, and the 935 is more accurate for me. Keep in mind there are a ton of variables that affect OHR performance, like skin color, position of the sensor, individual anatomy, etc. Given the stellar reputation of the Scosche, and just the fact that the wrist is not the best place to pick up a pulse for OHR, I was not expecting the 935 to perform as well as it does. So... try the hard reset, and then if it still sucks, I'd open a case with Garmin as you may have something wrong with your particular watch. From my experience, and the handful of guys I know who also use this watch, it should definitely be providing more accurate results than what you're seeing.

Thanks, there is a lot of help there.

I would recommend doing a hard/factory reset on the watch first. I had all sorts of issues with the recent updates until I did that. It sucks, but it did fix the problem.

Were any of the problems OHR-related? You're right it would suck to do a hard reset, but it is worth a try!

Generally speaking, the 935 OHR has been outstanding for me, in every aspect. I used a Scosche Rhythm+, and the 935 is more accurate for me. Keep in mind there are a ton of variables that affect OHR performance, like skin color, position of the sensor, individual anatomy, etc. Given the stellar reputation of the Scosche, and just the fact that the wrist is not the best place to pick up a pulse for OHR, I was not expecting the 935 to perform as well as it does. So... try the hard reset, and then if it still sucks, I'd open a case with Garmin as you may have something wrong with your particular watch. From my experience, and the handful of guys I know who also use this watch, it should definitely be providing more accurate results than what you're seeing.

Good to hear, both your experiences of the 935, and of the Scosche. I find the 935 a v "professional" piece of kit in almost every other respect (the wifi being a minor niggle), which in a way makes the OHR problems more disappointing.

When I was first researching this a few weeks back I found a great article where someone had actually done research on 20 so different people. The findings were that for most people it worked all of the time, like typical reviewers who post their own experiences with different devices in great detail, for some people it hardly ever works, and for others it works some of the time.

I seem to fall into the third category; it's worth trying a hard reset as you suggest, and definitely worth getting touch with Garmin support. I hadnt so far contacted Garmin support, because I had experienced wifi connection problems and users on this forum did not seem to get value from contacting support.

From my own experiences with the OHR, my suspicion is that my physiology changes day to day -- and even during the day -- but the watch, being electronic, doesn't, and so at particular times I can't get OHR to work at all, whereas at others it seems to work just fine.

If this is indeed the state-of-the-art view on the wrist optical heart rate on the forerunner,

It's not just the forerunner or indeed Garmin devices, it's virtually all wrist worn HR detection. There is no solution as the technology is not up to the task demanded of it, if indeed it ever will be. Some people report good outcomes, others absolutely no joy, and others in between.

at particular times I can't get OHR to work at all, whereas at others it seems to work just fine.

And this is pretty much where I sit. After trying to get consistent outcomes I now always use the strap for activities, using WHR only for tracking during the day if I'm not wearing my Apple watch.

Thanks, there is a lot of help there.


Were any of the problems OHR-related? You're right it would suck to do a hard reset, but it is worth a try!

Yes, all OHR related for me. It had been working flawlessly for me up until the 5.x firmware. It's working fine now again with 5.4, but only after I did a factory reset.

I do agree that OHR technology is spotty at best, and after my Scosche experience, I assumed I was just one of the folks who it wouldn't really work for. The 935 definitely changed that perception, as it's proven very stable and reliable for both resting and activities.

I see you mention it works best when you wear it "fairly tight"... Well, change fairly to pretty damn and I think you'll get there.

The OHR should be fixed really tight with as little chance of moving as possible, also wear it (slightly) above the wrist bone. Especially when running, I think it should first feel slightly uncomfortable even but that goes away quickly...But yeah, wear it tight basically!

Know how you feel. My optical/wrist HR is all over the place. Some days fairly good...most days terrible! Always wear it tight BUT if you're looking for accuracy then wear a strap.

@tg123
have you done a factory reset? Or any response from Garmin support? I have experienced the very same issue as you (recording a 20-30 beats higher using OHR compared to using a strap) and would be interested whether it has helped your situation :cool: