Max Heart Rate Updated Without Meeting the "New" Max Heart Rate During the Activity [FR255, bug]

Hmm strange behavior. 

I have quite a comfortable segment to test max HR. Last 500 m before my house I have to climb 30m high and if I feel good and have HR straps with me, I'll do a field test for max HR. The last time it was set was 178, I managed 185 and the watch wanted to set 183 at the end, which I then confirmed. I am 59 yo do 3x run and 2-4x bikes a week and find the values realistic for me.

Nothing beats the good old field test. Unless, of course, you die while doing this, but these are trifles in the pursuit of data accuracy. ;)

I recently upgraded from an FR245, on which I manually set MHR and HR Zones, to an FR255 on which I left on the default automatic MHR detection. Thus far I have only done a few easy base runs and one threshold run with the FR255. I've not gotten anywhere near MHR while working out with the 255 so far.

I noticed the 255 initially set my MHR about 14 beats lower than the max that had been recorded in the past few months on my 245. This figure was still 16bpm higher, and closer to my actual MHR, than the useless 220-age formula. Then it began adjusting it up after additional base runs.

I haven't considered this a bug, just the device making its best educated guess at my MHR based on what little data it has. I'm just leaving it alone and seeing how well the device does over time at estimating MHR. I have a couple of races coming up in 10-12 weeks and will be approaching, if not reaching, MHR in those events.

Has any one from Garmin stated that those at Garmin who are actually developing the algorithms have confirmed this behavior is a bug? A number of end users reporting this as a bug, which is understandable in the absence of a MHR recording, does not mean that the behavior they have seen on their devices is in fact a bug. Perhaps it is, or perhaps it is an ongoing process of the device making its best guess as it gets more data on the wearer.

UPDATE: I've been training with this watch for over three months now and, just as I suspected, the auto-detect MHR worked its way up to within one beat of the MHR which I had been using and reached during races several times in the previous year. It occasionally  adjust up or down a beat after a run. So in my brief experience this feature seems to work accurately given enough user data. It does not seem to rely on any previously existing data in Garmin, or it would have been much closer to my actual MHR initially.

My watch recently adjusted the max heart rate for running up a few BPM, even when the maximum heart rate reached during the activity was around 50 BPM lower. I was using wrist heart rate during this run, and would have preferred that the max heart rate was only automatically adjusted when I use my chest strap.

I would say that the algorithm is not that bad. During past 3 years, with another watch, I reached over 200 bpm a few times. Then, few months ago, I switched to FR255 and - as I don't trust computers too much - I've set manually 205 as my max hr. Since that I've had 202 bpm maybe once or two, but not even this year. Thus I decided that those might have been misreadings, I'm getting older, so I've set my max to 195. Few days ago, inspired by this forum thread I've turned on the automatic max hr and yesterday I did a hard run. I'm in a good shape now and I didn't even reach 170 bpm, eventhough I was really tired. To my surprise, after the training I've got info from FR255 that the new max hr was detected - and it was 206. It may be confusing for someone else, but still it all makes sense to me.

Garmin-Kevin - I've read through this thread and the much older 955 thread. Your last comment in the 955 thread said to see your updated comment, but I don't see a definitive post saying if this is a bug or not (maybe I missed it, but the updated comment wasn't clar to me). I have an open ticket with engineering and am trying to figure this out and it is killing me.

I have a 255 Music (firmware 16.19, but have been using the 255 for a year) and a Garmin HRM pro-plus strap.  I'm in the United States, am 48 years old and you can email me for more info / diagnostics / troubleshooting and you have permission to look at the data in my account and my ticket open with engineering.  I'm a very experienced and strong runner with a good heart, but Garmin's MHR auto detection seems broken and keeps setting mine to 192 no matter what I do. There have been zero runs (long, tempo, intervals, easy, any) with the HRM pro plus that show any heart rate of mine above 177, even after attempting two lactate threshold tests.  However, after every run, the watch resets my max heartrate to 192 (there was one wrist-only reading for one datapoint in August that showed that, but it was a false reading and I deleted that activity so it isn't even in my account). I manually reset the max heart rate to 177 in both the normal user profile heart rate profile area and in the running-specific profile (there are no other sport profiles), but then Garmin will reset to 192 after any run. I factory reset the watch and as soon as it connected to Garmin connect, it set both max heart rates to 192. I manually reset them to 177, went for a run and it reset it back.

When I attempt the lactate threshold test, it works me up through the stages, has me run at heart rate of 177 for 3 minutes (I can't keep it that high for 3 minutes), THEN it wants me to run for 3 minutes at 187 (because it keeps saying my MHR is 192). It isn't possible for my body to get into the 180s even running 5:30/mile pace but Garmin keeps resetting my max to 192, which affects the calculations of time in zones and the lactate threshold tests -- you fail the test if you can't do ALL the requirements, but the last one is impossible at the wrong/too-high MHR.

So this very much feels like a bug and I'm not sure what to do. I bought the HRM so I could get accurate lactate threshold readings and better zone configurations, but this MHR bug is breaking all of that. Even setting it to manual and entering my own number doesn't seem to work with the lactate threshold tests.

Any fixes, workarounds, or things I can do? Anyone else get this fixed? 

thanks

Dave B I have the same problem with my Garmin 255 Music. I'm 36 and just got into running, and my watch keeps setting my max HR to 195. I'm fit but not that fit. It must be somewhere in the mid 180s and not mid 190s.

Do you have max HR auto detection turned off?
I had an issue with my VO2 max estimation, which I described here: https://forums.garmin.com/sports-fitness/running-multisport/f/forerunner-255-series/332705/can-i-correct-the-vo2-max-estimate#pifragment-1279=2

Long story short - Garmin set my HRmax at 191. I didn't correct these settings for a long time, and my watch estimated my VO2max to be 48 (which I believed to be too high).
Then I did a field test to find my HRmax, and it turned out to be somewhere in the mid 170. I updated my settings on the watch to HRmax = 175. On my next run the watch wanted to update it back to 191. I turned HRmax auto detection off. For the next 2 months or so, my VO2max estimation was going down. Once it stabilized (at around 45), I turned HRmax auto detection back on. I haven't seen a single prompt to update my manually entered 175 HRmax anymore.

What I'm saying is - if you have a problem with HRmax auto detection, try turning it off for a few weeks, let the watch get used to your true HRmax (the one you set manually), then turn it on again

It is interesting to hear others with the same issue, but Garmin support sent it to Engineering and they immediately closed it out and said it is not a bug. If it is not a bug, then it must be a bad algorithm. Yes, everyone's heart is different and the old 220 - age is an estimate and not perfect, but should be in the ballpark, right? For me, if you take 220-48, you get 172. If you look at all my runs with the Garmin HRM pro-plus (including long runs, interval workouts, easy workouts, etc) my max ever is 177, but Garmin's algorithm keeps setting it to 192. That isn't even close. I'm curious how many 48 year olds even have a max heart rate over 185. I would expect it to be an insanely low number.

Anyway, I have given up on the auto-detect and disabled it and set my max according to the data I'm seeing with the HRM strap. IMPORTANT NOTE: It seems you have to manually set your heart rate in at least 2 places. 

1. click User Profile > "heart rate & power zones" > "heart rate"
2. Then click "sport heart rate" > "Running"  (there are no other sport profiles) > "max heart rate"
3. (and any other sports profiles there might be)

I also suspect the heart rate zones don't change once you override the auto-set MHR. When I went into the zones and toggled the "based on" to BPM, it was still using the 192 MHR even though I had manually overridden it. I had to click "reset zones" in both the main user profile heart rate zone area and the running-specific sports profile. It then adjusted the heart rate zones to my manual number -- then I toggled it to the "based on" setting I wanted, but since it still had the 192 in there, I didn't trust any of it was using the manual MHR until I did a reset. 

5925552 - congrats on being so fit. Sounds like you're working out hard and doing well! I'm curious - are you using only the Forerunner 255 or the HRM strap as well? I ask because (in full disclosure) when I was using only the 255 watch, I did get 2 over-190 MHR readings during runs when it was really hot here in Texas and a few in the 180s. However, I've been using the Garmin HRM pro-plus strap for several weeks now and have done 17 runs with it, including 2 lactate threshold tests (which are intense!) and hard interval track workouts, which push you to the max and the HRM doesn't show me going over 177 even when running 5:30/mile.  I'm not discounting what you're saying about being super fit, but now that I've been using the HRM, I don't trust the higher readings from the watch. Also, when doing the lactate threshold test, which was 30 minutes with a 1.2 mile warmup, 6 min at 144, 3 min at 158, 3 min at 168 and 3 min at 177, then 3 min at 187.  Whew. I couldn't get over 174 heart rate no matter how hard I tried and I was wiped. Based on that (and similar runs), I don't think my MHR is over 177, but that is just me.