Fenix 6 - HRM, VO2 Max, Race predictor all way off

Have you tried using a heart rate strap? Optical HR not always accurate.

When you say HRM, do you mean one of the HRM straps? Like HRM-RUN, HRM-TRI, or one of the other ANT+ units available? Is it paired with the watch?

Optical HR (which is what the watch uses without a strap) is imprecise, especially during vigorous exercise.. As watches get larger and more massive (and the F6 is MASSIVE), jiggle of the watch on the wrist during activity makes the Optical HR much worse. A lighter watch like Forerunner 245 may have much better OHR, but then you don't get the screen, battery life, and durability. Everything is a trade-off.

Any serious athlete should be using a chest strap, and you may find the added features of HRM-RUN beneficial if you are primarily a runner. OHR is fine for sleep and probably light walking/stairs, but don't rely on it for serious metrics.

Also: at 50 I would be shocked if your max HR was anywhere near 195. In peak cardio shape at 32, I could never crack 185 with truly all-out maximum effort up a steep hill, and that's exactly what the formulas predicted I should be at. Formulas for a 50y/o male suggest about 173-174 would be a 100% max HR. You could be over that, but not by ~20 bpm. I'm not a physiologist, but bad OHR would explain all of the problems you're experiencing. Get a chest strap and make sure the watch is using that data. OHR is improving with newer software updates, but I still recommend a real measurement.

P.S. I have an F6X Pro and for the most part it works perfectly. It helps to understand the technical limitations inherent in certain technologies -- like trying to read pulse ox and heart rate through skin on your wrist, or get accurate GPS position in a metal device 2" in diameter -- and I do occasionally want a small feature tweak here or there, but overall it is a spectacular tool.

Well, all these formulas for maxHR are crap. A lot of people don't fit to them although they are healthy. I'm 42 years old and my maxHR is 193 or even more. My doctor said that it's too high. Then I told him all my other HR readings and he looked at my with big eyes. I told him to throw that formula where it belongs to: the garbage bin. Then I should go to the cardiologist. I told her all my HR readings. She just answered that I'm a person with high HR. And she wanted to know what's my problem. Well, I don't have a problem with high HR but obviously all the other guys who call themselves doctor. They hang on to that crappy formula and not fitting to that isn't allowed to be. A lot of people are way off. It can be up to +/- 30 bpm! Even identical twins with the same shape and fitness can have more than 20 bpm different maxHR and not fitting to that formula.

Although I changed my maxHR to a measured value the VO2max is way off. Since one year I'm wearing the HRM Run but it hasn't changed. It's nearly 10 points too high. So the race prediction is garbage, too.

Well that may be valid because they are a large aggregation of numbers that don't capture outliers, but for me personally the formulas have been very accurate. Maybe I'm pretty average. 195 @ 50 is still crazy high, and bad OHR is a likely explanation for this reading.

I do use a chest strap at times (mostly to verify accuracy of other heart rate monitoring including the OHR on my fenix).I own a couple and have tried a couple others as well.

I do have an unusually high max heart rate for my age. This is why I am more keen to understand how the data is calculated by the watch software. Not knowing what is used to determine condition, and all the other workout metrics tends to make them rather useless if you are not "average".

As for the disparity from one workout to the next, that is probably just an issue of OHR not working that well as I had hoped, especially on my rather puny wrists.

But I have to ask @multiades, why would you say it is bad for me to have such a high heart rate max? Where does that determination come from?

I, like Carmin have heard that from people from time to time but never gotten that assertion substantiated from anybody.

My resting heart rate is down in the 40s and that is the number that generally carries weight when it comes to heart health.

It's unusual but I'm not a physiologist. There's a range that could be considered "normal" and you're probably outside of that, but it doesn't inherently mean you're ill as far as I know. I've been doing HRM-based training since before I had anything from Garmin (~28 years old) - including some extremely high intensity activities like continuous running of stairs and continuous running up a ~30% grade - and I've literally never hit your max HR at 50 years old. That's a sample size of one, so I don't think it should mean anything. The question it raises for me (if you're regularly hitting numbers like that), is: are you training too hard? The answer to that likely depends on whether you're a sprinter or a distance runner, but such high intensity should be used pretty sparingly from what I know. Admittedly, I'm geared for different activities these days.

The main point I wanted to make was that anyone doing serious training should pretend OHR is not even an option, and you shouldn't be too upset if the technology doesn't work well. It's far from the "gold standard" for athletic measurement and likely always will be.

Also, I thought Firstbeat metrics like VO2 max just ignore your zones and use only max HR and LTHR in the calculation, but it's possible redefining your zones may be important to the calculation. Unfortunately the zone scheme seems to vary based on different authors. The ones I read consider Z1 to be endurance aerobic from 55-75% of max HR, Z2 75-80%, Z3 80-90%, Z4 90-95% and Z5 > 95%. Z3 is given as Aerobic Threshold to Lactate Threshold, Z4 is above Lactate Threshold. Z1 and in very fit athletes Z2 is for basically ultramarathon-pace activities. None of this matches up with other representations of it, but it's what I use. I think Garmin calls Z2 what would be Z1+Z2 in my convention. They think of Z1 as warm-up.

Yes Garmin uses Age as a default Max HR, which is bad.  It doesn't update based on your run/bikes.  You need to set it to a correct or hypothesized value to make any of the watch analytics work for you.   So how to do that...

Looking at your past really hard runs could help, or end of a 5k race with a good sprint out.  Lets start with what you've given, without knowing how brutal of a run your 'threshold runs' feel to hit 195bpm a lot, if it was a true Threshold run, that would mean 195 isn't even close to your max.   You hit your max during 100% all out intense intervals.   So your max would be 205+ as a starting point.   However whenever using your workouts/race data in setting a Max, need to look at the graph of HR... does it look right?  Smooth, follows precieved exertion and pace?  Goes up on a hill... down on a decline...etc.   Ideally you'd use a HR strap to verify.   You can sort activities in Garmin by Max HR then filter through and find ones that are good candidates (super hard workouts, races, etc) many of them will be junk optical HR spikes that you can ignore (update the Max HR # in that activity to what you think looks like a proper real Max for future data cleanliness)

Google max HR test intervals... do that.  Also unless you feel like you gave it 100% perfectly! (white vision, can't catch breath, you can't run any more!) I'd add 5bpm.  Want to do the test when rested, cafeinated, ideally not early AM (HR is lower then...).    

I've also found newer/nice treadmill hand bar heart rate things are surprisingly accurate after holding for 5-10sec, so doing hill treadmil intervals work great also IMO.  Can use TM heart rate to cross check your watch as well.   

The first time I read this, I read "crazy high and bad."

My mistake. I now see it is "crazy high, and bad OHR..."

My true max likely closer  to 190ish but still crazy high.

The 195 are spikes and most likely inaccurate reads from OHR. But more to the point, my original frustration is that the data only has value if it can be relied upon. In the case of the Fenix,  the lack of accuracy of the OHR (for me), as well as the use of generic formulas make all the race predictors, VO2Max values, suggested recovery, etc. useless. Additionally, I challenge the assertion that this is more a problem for those that are serious about their training, because those that are less serious are likely to have less information and are more likely to rely or accept the predictions or suggestions that the Fenix is spitting out.

That said I am a big fan of the mapping capabilities of the watch and ultimately am glad I can stick with my long held belief that the most valuable metrics are simply time over distance and perceived exertion.

Now I just gotta stop looking down at my wrist and feel it!