Garmin FR955 unreliable for running competitions

Thanks for the tip about Runalize. VO2max is not that important to me It shows a trend as my condition improves. At least, before....But now it says nothing because it shows nothing. That changed last year because before I definitely could see the difference in periods of less training. But now it is only a number. I like to see improvements Or not  . So it is all related to ech other. But it is clear that the predictions for some of you works well. 

Now it makes sense why garmin would update my v02max way more frequently when I was using a chest strap.

Why? Pulse measuring may not be as accurate as the strap but averages should be fine when garmin filters the "strange" rates out? pulse measurement should do the same OR Garmin must say you need a strap if you want to use VOmax, racepredictions, etc. 

Based on what I know, Garmin bases its analysis also on changes in heart rate variability (HRV) during the activity. And that is much more accurate when you have a HRM strap capable of measuring timing of individual heart beats. Also, a HRM strap can notice rapid heart rate changes much faster and more reliably.

Yes I know. I ran for years with a strap. But now the pulse sensors should be good. The point is, if measurements on pulse is inaccurate ie for running. Garmin has to say so. Then you have to buy an HRM strap and spend another > € 100,- . In that case for me as a runner there are maybe better and cheaper watches to get this?

Maybe someone from Garmin can say something about this?

"there are maybe better and cheaper watches to get this?" No

You can get a Polar H9 for 50€ on Amazon if really needed. But with an accurate maximal HR you should be fine.

Does the HR data during your runs seems fine?

I think the truth is that we have to accept that wrist is just not the optimal place to get heart rate or other running-related measurements. Which is sort of logical, since we are talking about measuring at the end of a wildly moving extremity, which is not itself responsible for the actual movement. In that sence, a strap that directly measures electrical impulses right next to the heart muscle is always going to be more accurate and reliable. And the same goes for running dynamics measured from the wrist. The only thing that you can get mostly right is running cadence, since the arms are mostly waving to the same rhythm as the legs.

But still, I'm not 100 % sure I know what "inaccurate measurements" you are referring to? As others have pointed out, if the max HR is accurate in the watch, VO2max and others should be ok as well, with the exception of short speed intervals, where wrist optical HR has no chance of catching up.

OHR are never accurate for me. Today for instance I forgot my strap on a VERY easy run/walk  with my partner and it said at some stages I was heart rate at 145 bpm , I assure 6min/km is not that for me! It must have been at least 20 - 30 BPM too high. 

My experience is that the HRM strap seems faster to re-act and my pulse is different from the one on the watch. 

As far as I can se of my recordings It is releated to how tight the watch is to my wrist,  and also the "registration area of my body" is smaller on the wrist than on my  chest.

As I am doing a lot of MAF-training then i am always using my HRM-belt.