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heart rate totally wrong on my new Forerunner 945

Former Member
Former Member over 5 years ago

I had a VO2max of 37 on my old Forerunner 645 - after 5 Weeks now, running with the new 945 it dropped to VO2max 34. This is very frustrating and demotivating.
I did some runs with both watches and the heartrates were far from each other sometimes higher, sometimes lower, never near .....
Just to check which one is wrong, I Did a IPN Check with my Doctor on a Indoor Cycle.
I was totally shocked how bad the 500$ my Garmin 945 is when it comes to heartrates...

Here are the readings in 30 Sec Intervalls (from 25 to 100 watts)


Doc Garmin    Div.
89    117    28
88    123    35
87    122    35
91    135    44
96    134    38
96    134    38
100    118    18
98    113    15
103    127    24
106    108    2
107    110    3
110    117    7
115    119    4
119    124    5
123    127    4
127    123    -4

Totally crap. I cannot do workouts if the ranges are so wrong. How should  I trust ANY of the Garmin values if the basic one is so wrong?

Is may watch broken?

please help,
thank you

  • 0 over 5 years ago

    It's not broken. There are big limitations regarding OHR precision. One of them is cycling. It's not Garmin fault, it is the limitation of the current wrist OHR technology.

  • 0 over 5 years ago

    From this morning's run... Using the Auxiliary Heart Rate widget (Wahoo heart rate strap) and the FR945. I see zero issues when running.

    Now, Strength training, I have to wear the watch a bit further up the arm to reduce issues with gripping weights, and use a sweat band to keep it in place to get good results, but even then, those results do not look perfect. 

    This grip issue also happens when I bike. I have to be aware that movements while biking can cause the watch misread HR.

  • 0 over 5 years ago
    I did some runs with both watches and the heartrates were far from each other sometimes higher, sometimes lower, never near .....

    If you were using a HR strap, then you may have an issue.  If the differences were between the oHRM sensors, it may be because the 645 uses the generation 2 Elevate sensor and the 945 is generation 3.  I have watches with all 3 generations (235, 935 and 945) and I notice a difference between all of them.  I think Garmin's oHRM has gotten better with each progression.

  • 0 over 5 years ago

    just use a heart rate strap for best results. thats all. never problems even on my older 920XT watch

  • Former Member
    +1 Former Member over 5 years ago

    thanks a lot for your answers and very fast response.

    I'm using a Garmine-Tri for running, but did't connect when checking the two watches against each other in the same run.This generation thingi makes sense.

    I thought the cycling - issue is only on mountain-biking caused by all this little bounces and shocks. I was not aware that it could be a grip (pressure) thing.

    I will will make some more test.

    Right now I am happy that this seems to be  common problem and not a broken watch. But I am really very sceptical about all this nice Garmin evaluations, though.

    Thanks again!