Fenix 5S HR monitoring is grossly inaccurate?

I got my watch about a week ago, installed all the proper updates, and have been using it daily. I have noticed an issue with the HR monitoring across the board. I primarily do CrossFit, which means my activities vary from lifting to running to random cardio movements to strength. I can push myself to the brink and be lying on the floor breathless and the watch is reading my HR as something like 110 or even as low as something like 84. The only time I seem to get any semblance of accurate HR is if I am actually running or jogging, with my arms pumping. When I check, I will then be in the cardio zone with something like 140-150. Other than that, my watch does not seem to pick up changes in HR accurately. I have tried the strength setting, cardio setting, etc and was starting to think maybe I needed to update my software, but it is up-to-date. I have also tried re-positioning the watch on my wrist, as well as both tightening it and loosening it. Nothing I have done has seemed to improve the HR monitoring.

Note: I previously had the Forerunner 225 with HR monitor, so I am familiar with the wrist HR monitoring. I would have issues from time to time with that watch's HR monitoring, but not like this. I recognize that wrist HR monitoring is less accurate than a chest monitor, but I have upgraded my watch (at a hefty $$$) for what appears to be less accuracy.

Can anyone help? Is anyone else experiencing this?

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0 Richard2145 over 7 years ago

I have a similar issue. Using the Fenix 5S with all the updates done. I wear a Garmin HR chest strap and use strength setting. My heart rate goes between 120 to 160 during the workout which is correct. Then I do the same workout a few days later and use the 5S wrist HR and the heart rate goes between 65 to 85 which is grossly incorrect. I then stopped this strength workout, put on the HR chest strap and start another strength workout. The watch connects to the chest strap and my heart rate goes up to 130 to 160. There appears to be a bug when using wrist HR during strength.

0 Dr Phil over 7 years ago

It's not a bug. It's a limitation of WHR. Do a search in the forum and you'll see the same comments time and time again for devices with WHR. While it might be perceived as being better or worse with some devices, the reality is that for 'active' activities, forget about getting meaningful results from WHR and use a chest strap.

0 Richard2145 over 7 years ago

I know that WHR are inaccurate from chest strap. This is what I have read in forums. For example a chest strap reading of 160 I would expect inaccurate readings from a WHR of anywhere between 150 to 170. We all know that WHR are not as accurate as chest straps. Now back to my bug. A chest strap reading of 160 with a Fenix 5S in strength workout gives a reading of 70-90 with the WHR. This is not an inaccurate reading but something wrong with the WHR in strength workout. Oh, by the way using the walk or run workout and with the WHR I get readings within 2% of what my chest strap gives. So this tells me that the WHR does work properly in walk and run but when in strength workout it does not work properly.

0 Dr Phil over 7 years ago

So this tells me that the WHR does work properly in walk and run but when in strength workout it does not work properly.

And you'll find no end of other posts from people that have reached the same conclusion. Well apart from the run bit anyway.

0 JGadell over 7 years ago

I have yet to compare mine to a heart strap. Tightening mine up and placing above my wrist bone seems to operate well. attached are just 2 different sessions. The one with the drop in HR was me taking it easy on the rowciq.forums.garmin.com/.../1236821.png

0 JGadell over 7 years ago

Not saying mine is perfect but maybe I got lucky? I also have yet to do any beta software. The way it came out of the box is the way she sits.ciq.forums.garmin.com/.../1236825.png

0 l0nepinemall over 7 years ago

It's not a bug. It's a limitation of WHR. Do a search in the forum and you'll see the same comments time and time again for devices with WHR. While it might be perceived as being better or worse with some devices, the reality is that for 'active' activities, forget about getting meaningful results from WHR and use a chest strap.

I guess I am just confused on this. Should I track ALL of my activities on something like run instead of strength or cardio? My old Forerunner 225 only had an option for RUN, so I did all of my CrossFit workouts under run. Had no problems with accurate tracking (minus small issues here and there) in this format. Is the issue with the 5S simply because I am choosing strength? Or cardio? I find it odd that a newer watch would have WORSE WHR technology and accuracy simply based on what activity I choose? This makes no sense.

0 l0nepinemall over 7 years ago

I know that WHR are inaccurate from chest strap. This is what I have read in forums. For example a chest strap reading of 160 I would expect inaccurate readings from a WHR of anywhere between 150 to 170. We all know that WHR are not as accurate as chest straps. Now back to my bug. A chest strap reading of 160 with a Fenix 5S in strength workout gives a reading of 70-90 with the WHR. This is not an inaccurate reading but something wrong with the WHR in strength workout. Oh, by the way using the walk or run workout and with the WHR I get readings within 2% of what my chest strap gives. So this tells me that the WHR does work properly in walk and run but when in strength workout it does not work properly.

This is exactly what I am wondering. I will test today during my workout and select RUN, even when I do strength/cardio/CrossFit movements and see what my results are. If they are closer to accurate, then I guess I will have to select run every single time I workout. Seems 100% like a bug, if you ask me!

0 peteholloway over 7 years ago

I guess I am just confused on this. Should I track ALL of my activities on something like run instead of strength or cardio? My old Forerunner 225 only had an option for RUN, so I did all of my CrossFit workouts under run. Had no problems with accurate tracking (minus small issues here and there) in this format. Is the issue with the 5S simply because I am choosing strength? Or cardio? I find it odd that a newer watch would have WORSE WHR technology and accuracy simply based on what activity I choose? This makes no sense.

I don't think it has anything to do with the app you're using. WHRM is just very bad at detecting a sudden change in HR, like interval training.

0 scottj2 over 7 years ago

Optical heart rate monitors suck in general for gym and crossfit type activities. The constant movements of your muscles and the fluctuations in your heart rate make it difficult to track your heart rate. I'm actually surprised you had good luck with the 225 to be honest, because I had terrible luck with both the 225 and 235 for anything other than running. I'd be very surprised if changing the activity app fixes your hrm during strength workouts. If you find that to be the case, definitely post back and let us know.