Garmin wrist HR Vs strap in TR

My forerunner 255 HR looks correct when walking/gym stuff however when I’m on tr with my wahoo HRM connected to the PC it’s low, more like my general pottering around HR whereas the strap is at at I a level expected for the effort putting out.

Also checked my HR with a app on my phone using the camera and that’s in the strap level.

I’m not worried per se since I’ve got a strap but more puzzled what is going on.

I don’t think it’s a tr issue but I know lots of people here have Garmin watches.

My 735 needs 8 minutes to realise I’m doing something hard. Maybe you looked a bit too early?

In general, optical HRM are thought to be less accurate, and are also affected by other factors more easily. Dark skin, scar tissue, tattoos, or how tight you wear it, can all affect it.

I believe other watches handle it better but my Vivioactive optical HR sensor on the wrist is terrible for HIT/ cycling; for Tuesday it recorded a max of 131bpm and the chest strap recorded 176bpm in a HIT session and 175bpm on the commute. I think there has perfect contact between the wrist and the sensor with no light interference, no movement. Higher intensity stuff doesn’t facilitate that.

I find it beneficial to think of the watch HR as a health tracker (sleep, resting HR, etc). For accurate HR during activities you need something else. Chest strap, optical strap higher on the arm, etc.


I have a well rated chest strap, a peer-review-study approved armband optical, and a wrist-based OHR, all from different brands. All read differently. I’ve broadly given up and just look at relative climb and fall vs absolute number.

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This is exactly my experience with my Vivoactive sensor! For stuff like RHR etc its good (or at least consistent) but anything where I start to actually raise my HR under load it struggles.

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I have the same issue with my 955. I’ve given up using the watch for hr on the bike.

I wear my HR strap instead and sync it to the watch with ant and TR with Bluetooth. Only way I’ve found to solve the problem.

To me it looks like the watch looks for HR in certain bands (RHR, light activity, heavy activity) and once in that band, it is pretry accurate. But it needs a bit to realise that HR has moved into a different band.

For me at a start of a cross race, HR stays at “light activity” level for 8 minutes after the start, then it jumps to threshold and seems to record accurately (ie, slightly up and down depening on features on the course). It should obviously go to threshold much sooner, there is likely even a near-max reading from the start effort that goes unoticed.

Recording another high-intensity activity just before sometimes helps, and it reacts straight away with the second activity.

You need to make sure you have your watch set to Broadcast HR or be in an activity for accurate HR readings during activity. It ups the power to the LED.

It also pays to make sure it is sinched up firmly on a fleshy part of your arm, not on the boney wrist area.


I’ve actually found a forerunner optical sensor to be more accurate than a Garmin HR strap for me… but I have pale skin and I suspect that I produce the wrong kind of sweat for good conductivity, or the wrong shape chest for good contacts, whatever the reason, a Garmin strap gives a lot more dropouts than optical.

I’ve even recorded effort tests as ‘indoor bike’ and the optical reading has been within a couple of BPM of the big machine (steady increases in effort so no intervals where you’d see lag from the optical reading).

I also find that the watch sits well on my wrist - in answer to the original post, are you sure that it’s tight enough, and different hand positions aren’t messing up the reading?

My Garmin 735xt is pointless for HR. My Garmin chest strap is always accurate. The watch has my HR at over 200 sometimes when my max is 176bpm. That said it’s only an issue when I run as I use a chest strap when I TT or any type of ride whereas I just use the 735 for running. I have a Forerunner as well that’s exactly the same - you can’t measure HR with a green light on your wrist…well not yet!


I’ve had this issue since moving from a 235 to a Garmin Instinct Solar approx 2 years ago. I had multiple toing and froing with Garmin support, with them doing themselves as MASSIVE disservice regularly stating that the the wrist HR would be affected by bent wrist on the bars, lifting weights etc. THIS IS NOT THE CASE.

After a lot of scenario and option testing I found all you need to do is start an activity and it uses a different sampling method and is really pretty darn accurate. You can then delete the activity afterwards and it’ll still keep the HR data.

I set up a seperate activity on the watch which I use while doing TR or an outside ride on my 530. I then junk the watch activity after TR/830 sync.


Same here. I’m not a heavy sweater, so HR bands tend to give me inaccurate results, especially at the start of a workout. I’ve gotten in the habit of applying electrode gel to the band before putting it on, and that makes the problems go away.

That stuff never worked for me but it was probably a sign of my then underlying problems. Now they are sorted I sweat like a pig :joy:

Ok this makes sense. My 945 just on my wrist never breaks 100 on a trainer ride (or outside recording on my edge) even when my strap is reporting to TR/ edge that it is 160 (or whatever). My dad has a 935 and says his matches his strap in TR but he tends to dual record. I’ve felt that it reads correctly while using it to swim or on a hike, and before I got the hrm-pro it was working fine on runs.

I don’t necessarily care enough to bother with settings but it has annoyed me that it seemed the HR chart in the connect app and the max for the day never lined up. As in one was taking the data from the strap/trainer ride data but the other was relying on the watch. For some reason I am now blanking on which was which.

Ah ok. I’ve never seen this, because I only ever use my 945 for HR, never a strap. So whenever I’m riding indoors with TR on a PC, or riding outdoors using an Edge 530, I’m still using the same Optical HR, and I’m broadcasting from the watch (not even dual recording). For my skin/blood/wrist shape it’s super reliable.

In fact I do this often enough that I set a shortcut - long press on the Start button now opens the Broadcast HR screen, so I don’t have to go through a bazillion badly named menus.

This used to work perfectly on my 235 watch. Unfortunately it doesn’t work on my Instinct Solar, I HAVE to be recording an activity for it to sample correctly. :frowning: