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Heartrate so inaccurate that my watch is basically useless for training

Matt S.
8 months ago

I got my Forerunner 265 about a year ago and I have loved almost everything about it.  I love the touch interface, the AMOLED screen, sleep analysis, training readiness, etc.  But I have been trying to use it to track my training and the heartrate is so inaccurate that it is basically useless.  Today was a good example, I just wanted to go for a 40 minute run on my lunch break.  I took the watch off, cleaned the sensor, strapped it snuggly on my wrist in the suggested spot and headed out on a run.  My goal was to get some good Zone 2 progress.  Instead one minute into my run, I glance down and I'm in zone 5.  I check my heart rate manually and I'm actually in zone 1.  I let the watch calm down and try again.  Same thing.  I do this for two miles.  I eventually discard the run because it's so crazy.  But now I've run 2 miles that won't be recorded.  Not the end of the world.  But my lunch break is almost over so I try again.  Basically the same deal.  I keep stopping to let my watch try to get in sync with reality, but by the time I'm done my watch now thinks I was doing an interval workout.  Having gone through this frustrating process a few times, my mileage, my load focus, my max heart rate, my training load, basically everything are now all out of whack.  Can't get good heart rate data running, biking, rowing, or stair climbing Disappointed

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  • 0 4 months ago in reply to Thibaud J

    I have one data point of my chest strap messing up in the exact same way that the optical heart rate monitor does. I let Garmin know this week about it along with some other data and they chucked it up to sweat or dirtiness or cleaning or something else. 

    Well they might be right, it also opens. Thought of the idea that the issue isn't a sensor itself, but how the data is being interpreted by the watch.  

  • 0 4 months ago in reply to Thibaud J

    For nearly a decade I used my 920XT with a HRM Pro with fast and accurate results. I recently purchased a Fenix 7 Pro with the hope that optical technology (especially from a company like Garmin) would have advanced to where I could hang up my chest strap which I hate wearing. I compared the Fenix 7 on a virtual bike ride to 3 other devices, my 920XT w/ chest strap, a Polar optical arm strap displayed on my trainer software (Zwift) , and my Apple Watch 8. All 3 read exactly the same but with the usual lag with optical sensors but the Fenix 7 was never even close. Tried some adjustments with no success. What surprised me most was that the Apple Watch was much better than the Fenix 7. I sent the Fenix back and for 40% less got the ForeRunner 965. I love the watch but the HR is no better than the Fenix 7. What the *** is wrong with a sports watch company like Garmin if they cannot produce a watch that can compare HR accuracy wise with a watch like the Apple Watch which wasn't originally designed as a sport watch. All I can say is that if someone needs accurate HR don't buy any Garmin product. Their optical HR sensing technology absolutely sucks.

  • 0 4 months ago in reply to Thibaud J

    Recently, garmin made changes in this regard and the watch may use the wrist HR sensor instead of the chest strap silently, when it decides to do so.

    So yes, any HR from that point can be considered as faulty on watches (even when using chest strap). 

  • 0 4 months ago in reply to pxl

    So far it does seem that as long as you have an activity started it will use the chest strap but when you end it it goes back to the watch sensor. Garmin told me that there was a way to turn off the optical sensor in the settings but I haven'y found it yet.

  • 0 4 months ago in reply to soutback11

    Any way to get both?  I'd love to have both the watch and the chest strap data to compare.

  • 0 4 months ago in reply to soutback11

    This from my 965 but 265 may be similar.

    From HR Glance select settings (top Right)

    Source Switching to Off - Then it won't try to use OHR with Chest Strap connected. I have mine Off. (This is a new setting that was introduced after the debacle of having OHR always active even if HRM was attached.)

    PS you can only see this option (I believe) if you have a HRM paired. (Which makes sense)

    If want to see both download the .fit file and interrogate it (Obviously the Source Switching needs to be on for this so the OHR registered)

  • 0 4 months ago in reply to Matt S.

    See the reply I just did so southback11

  • 0 4 months ago in reply to S.M.R.

    Thank you. Found it!

  • 0 4 months ago in reply to Garmin-Sierra

    This problem will make several users think twice before replacing their current watch by another garmin. 

    I´ve bought the Forerunner 265 almost a month ago, I thought the sensor would "learn" or calibrate with time, but after severals runs this problem still persists. Yesterday I had interval session and because of this problem, nearly half of the first two intervals showed nonsense behavior:

    On top of that, these errors will drastically affect the calculated performance, VO2 max, and several other metrics calculated by the watch. 

    Hope  will launch an update really soon. 

  • 0 4 months ago in reply to Mat

    If it makes you feel any better I think it is a problem with all of the Garmin newer optical sensor watches. I recently wanted to update my 920XT ant the same time see if I could get away from wearing the chest strap so I purchased the top of the line Fenix 7 Pro hoping it would have their best sensor for nearly $1K. Did a test using 3 other HR devices, 920Xt w/chest strap, Kickr Bike w/Polar optical arm band, and an Apple watch 8. Those 3 devices read within 1 BMP (except for the expected lag with the optical devices) while the Fenix was out generally by 10 BMP some times sitting at that number as I changed my level of effort while the other 3 responded to the reduction in effort.

    Sent the Fenix back for a refund and bought a FR 965. Similar issues with the built in sensor as with the Fenix. However for nearly half the price of the Fenix it has almost all of the same features (some of which are nice) so I'll just wear my chest strap with it.

    I think it is agreed that the only thing optical has going for it is convenience other that that it will never compete with the chest strap. However, with that being said the Apple watch is pretty damn good.