Forerunner 235 heart rate monitor accuracy (again)

They aren't natural, your heartrate can vary of course and is likely to increase during the run... But not like this.

The higher heartrates (going to the 170/180 range) are possibly cadence lock (cadence isn;t shown in your screen so hard to tell here). What that means is that the sensor is locked to your cadence (likely due to the movements caused by landing on your feet, or the 'differences in pressure' due to the drumming of your feet so to say.

The best way to avoid these (partially) is to wear the watch higher up your arm, and tight! I still can't completely get rid of them though just yet, might also be that my watch slips down slightly causing it to sit less tight and as a result them to appear again.

Low HR isn't explained by this though, but temperature can also be an issue...

So no, it isn't natural but unfortunately you're not the only one. It's partially a result of the OHR on wrist technology, but imo also part of the way Garmin handles this (again, never had this issue with my TomTom Cardio).

Wearing it higher up my arm helps me with the more accurate reading as well (as in, I had some low readings earlie as well... don;t think it happened since wearing it differently).

Anyway, worth a try for you but I still find the OHR solution by garmin sub-par and surely hope they improve this.

The cadence lock, low-temperature : low-heart rate, and inaccurate all-day-heart rate issues have rendered the heart rate sensor worthless for me on my 235. Yesterday I ran an easy 3.5 miles on the treadmill and it is the first time in weeks that I didn't get a cadence lock. I imagine if I had ran longer I would have though. This morning, my "all day heart rate" read 141 -- while driving to work. I logged 559 "active calories" so far today from taking only 810 steps.

While it struggles with intervals, the Fitbit Charge HR never once struggled with either of these problems. It is unacceptable that Garmin has not resolved these issues yet.

I made the decision for now to disable the heart rate monitor and move back to a chest strap. I paid a premium for this watch over the 220 and I'll never get that back, but I guess that's how it goes.

Thanks FlipStone and ascii256. I guess I am not alone and more browsing in the forum confirms this.

I will try wearing it further up my arm and tighter and see if this helps. It sounds, though, as if I shouldn't expect too much unless and until Garmin do something to fix it. I assume this might be possible from a firmware update?

Thanks again for your help.

Due to a knee injury I don't run as much and often as I'd like so it's hard for me to properly test atm but I do feel that wearing it higher up the arm seems to help, it at least gives me hope...

Then again, this is something Garmin should indeed address further but to be honest that gives me not as much hope. So far their updates haven't improved too much and the radio silence in this specific area is worrying for me...

Has the cadence lock bug been fixed yet?

Reason I ask is that no matter how fast I am running, my HR is always reported by the watch as Threshold (with the exception of a really speedy short sprint when it would hit max). Makes no difference whether I am running a 7 minute mile or a 10 minute mile!

If I stop to rest it does tell me I am in recovery rate as my HR drops, but most of the time otherwise I am in threshold even if doing an easy paced run.

Why do you think that is automatically a cadence lock issue, though?

Reason I ask is that no matter how fast I am running, my HR is always reported by the watch as Threshold (with the exception of a really speedy short sprint when it would hit max). Makes no difference whether I am running a 7 minute mile or a 10 minute mile!

What is the range to which your Threshold HR zone (Z4) is set on the watch?

what is the range to which your threshold hr zone (z4) is set on the watch?

172-183 bpm

perhaps I'm just not as fit as I thought! :p

i have default heart zone and FCMax (185) set up
on 50% of my activities i can see FC jump from 150/166 bpm to 200/220 in a very short time.... very strange cause it is not on every activity

For cadence lock, a higher cadence is helpful. It should be minimum 170ish. Also, experiment with where you have your watch on your arm and notice the performance. My experience is that it works best where my wrist are the thinnest. And it's tight, but I am able to have it one hole tighter than I do. Hope you will figure this out.

Hello,

I have exactly the same issue : on some activities the HR jump 20 bpm and never come back to normal level. Do you still have the issue ? Is it a global problem or only mine (& yours) unit ?