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Forerunner 255 VO2 Max way off and barely adjusts (Algorithm problem)

ThePhoenixCoding
over 2 years ago

I have a FR 255 Music for about 2 months now (Firmware 12.27) and experience a severe problem with the VO2 Max calculation. I believe this is due to a bad algorithm and Garmin should take a look at this. Might be related to:
https://forums.garmin.com/sports-fitness/running-multisport/f/forerunner-955-series/304806/vo2max-isn-t-increasing

I am 26 years old, female, 1.83m, 66 kg and just started running again. About 4 weeks ago I started running again with the following results

  • 20.10: 1.63 km @ 9:22 min/km @ 134 avg + 155 max HR (quite tired afterwards)
  • 16.10: 0.88 km @ 5:40 min/km @133 avg + 174 max HR (benchmark run, all out and not able to walk afterwards)
  • 3 max HR tests, all resulting in MHR = 185

As you can see, my VO2 Max propably should be below 30, but it started off with 46. I believe this was the last reading of my Vivomove HR from years ago and it was displayed eversince.

I logged 10 runs in the last 4 weeks with the recent 5 of them meeting the requirements for calculating VO2 max (>10 Minutes of constant running, outdoors + GPS, HR measured and HR > 70% of MHR). I greatly improved during this time, now I'm at:

  •  05.11: 3.02 km @ 8:18 min/km @144 avg + 162 max HR (feeling good afterwards)

The watch and Garmin connect still display my VO2 Max at 46 with the graph at the watch showing that in decreased by ~ 0.6 in the last 4 weeks and it still decreases after every run. It even knows that it's way off and tells my by giving me a performance condition of -10 to -20 every time. This is really frustrating as most of the training features the watch might offer me are useless. My optimal window for acute load is barely reachable, my power condition is always very negative, my VO2 max readings don't display my progress and as a result my training status doesn't reflect that I'm improving. Seeing one's progress is like half the point of buying something that produces tons of metrics. Also the recommended trainings are not doable and the race predictions are useless.

I tried deleting my VO2 max from the user profile, turning True Physio off and on (and having a run in between) and researching the heck out of it. I finally found out that the VO2 max algorithm seems to be modified to only do very small steps with the recent *55-devices (see link above). But this is absolutely useless if it doesn't do big steps in the beginning (including recalculations after long breaks with no recorded data) to even out misreadings. Especially, if it (intentionally or by accident) uses years old values as baselines.

Maybe Garmin can take a look at this and fix the algorithm. My assumption is that it used the old value from my Vivomove HR and because it's so old, the algorithm immediately jumped out of its initial big-step-phase and only adjusts in tiny steps. If it even has a phase with bigger jumps to begin with (which it really should have!)

PS: This is runalyze's take on my VO2 Max:

Related complaints:
https://gadgetsandwearables.com/2022/08/16/garmin-forerunner-955-vo2max-222/
https://www.reddit.com/r/Garmin/comments/wpdzge/is_it_harder_to_increase_vo2max_number_on_955/

  • 0 over 2 years ago

    I just realized that this leads to another bad implication: If even in my extreme case the algorithm fails to adapt to an increasing or decreasing VO2 MAX, the whole training status becomes useless. It would take months to discover any kind of overtraining oder undertraining, even if the baseline VO2 MAX was correct, becuase the VO2 MAX figure just doesn't change quickly enough.

  • 0 over 2 years ago in reply to ThePhoenixCoding

    I don't think Garmin knows that you have been skipping exercise for a long time. You could have been working out with a Polar or Fitbit in the missing time. It will make a best guess that your shape is the same as last time you were uploading workouts, and go from there. As shape doesn't change very fast, it will adjust slowly, as that works best for most Garmin users. Sometimes this will lead to very wrong data, like in your case.

    I have had a virus for some weeks, and have not been able to run. My watch assumes I am in a terrible shape. After jogging a 10K in 62 minutes today, it reports that my race prediction for 10K is 68 minutes! :-)

  • 0 over 2 years ago in reply to ovekvam

    Even in this case, I'd say that the algorithm should be highly flexible if there's not a lot of recent data available. Even if I trained with a Polar during that time, Garmin doesn't know the state of my fitness anymore and it could have changed a lot  (for better or worse) in the meantime.

    If the algorithm would stay dynamic in such cases, the worst thing that could happen is that it fluctuates noticably for a few trainings (which is what you would expect from a watch that you didn't use for quite some time anyway).
    But the way it is now, everyone who used to have a Garmin and uses a _55 watch now will have false VO2 MAX readings  for a long time and thus mostly useless metrics and recommendations, if their VO2 MAX changed in the meantime.

  • 0 over 2 years ago in reply to ThePhoenixCoding

    What is the Time/Date vo2max  was calculated? It is directly under big vo2max digit on display. Can it be, it's only old Data and new one was not calculated?

    Have 255 my first Week(after VA3) and all metrics seems to be all OK. VO2max can't change in weeks, may be months or years of training. It's genetically and not vary that much. i would say early was "wrong" estimate for a vo2max.

    Runalyze calculates more likely VO2, not max. If you see your laps, every time it's different  vo2max. Your blood changes every km? Every workout? Really? Really not. And 1st or 2d km has your predication for vo2max. with many others assumes - you have "normal" fitnes level, running efficiency and s.o.

    If you have had 46 and 26 yo it's not so much, but it's yours  :) /in Garmin Version/

    vo2max is not only fitness marker, but one from many others - see HRV, BodyBattery.. All together they lead you to be better. I assume Slight smile

  • 0 over 2 years ago in reply to global_local

    Thanks for your reply!
    The VO2 MAX of 46 can only come from old recorded runs between 01/2021 and 05/2022 which is the time I used the Vivomove HR for. And yes, I did have recalculations for the recent 5 (by now: 6) runs. As you can see in this Runalyze screenshot, the VO2 MAX calculated by Garmin ("VO2max (Datei)") did indeed decrease over the last 6 runs and my watch started to confirm these values. Runalyze on the other hand calculates very plausible VO2 MAX values ("VO2max") .

    I totally see that it can make some sense to make the algorithm quite lazy, depending on what you prefer. I would prefer it more heavily adjusting to sickness, but that's just a question of taste. If you went to the doctor and have it measured professionally, you would also see the influence of being sick.
    But having a lazy algorithm just makes it more important that it starts with a somewhat reasonable baseline and if it detects that your current performance is off by a lot (20 points in this case), it must adapt. At least by asking the user if we want to recalculate from scratch because of unplausible data or something.

    By the way: It's not important in this debate, but your VO2 MAX is mostly dependent on your training status and not on your genetics. Normal people can put themselves in a range between ~20 (very unfit) and ~70 (very fit), not to mention even lower values for obese people and even higher values for professional athletes. Your genetics just determine some minor biases and the upper achievable limit.

  • 0 over 2 years ago in reply to ThePhoenixCoding

    Have you tried to enter a low value manually for VO2Max in your profile? 
    By the way, I don't think any professionals would agree to measure your VO2Max if you were sick.

  • 0 over 2 years ago

    If I were you, I would re-set the watch to factory settings, remove the device in Garmin Connect, and re-initialize everything with Physio TrueUp turned off. If you're right and the problem are the old values, then maybe this would prime the watch and make it start from scratch?

  • 0 over 2 years ago

    Also, my experience with runalyze vs Garmin is that Garmin always shows larger VO2max values for me. It's because those two models are different. Probably Garmin takes into account more fitness-related things (who knows - stress level, sleep, but also running dynamics and efficiency), while Runalyze really only takes into account your max HR and your running pace. Hence, Garmin might sometimes be right saying that technically your VO2max is higher (as you would measure it in a lab), it's just that your current overall state doesn't allow you to run with the maximum efficiency for that VO2max level.

  • 0 over 2 years ago

    Thanks! Yes, I did try to set the VO2 Max manually and also tried to delete it. But unfortunately I can only confirm the experience of other users: Nothing changes, it's just cosmetics for your profile.

    I think the full reset of the watch, maybe even if my whole account could help, but I don't think it would be worth it as I'd lose the calibration of my HRV (and with it the calibration of my stress levels and body battery) too and the VO2 Max history won't be complete anyway as it would miss the first 11 workouts by now. It's still very frustrating but at least I have the full VO2 Max history in Runalyze (even with a different calculation method then) and the problem within Garmin will resolve in a few month when my fitness will be greatly improved and the value on the watch will be decreased.

    Thanks also for your experience with Garmin showing higher values. I don't think that this is the case here though as the steady decline in Garmin's calculation kind of proves that it knows that it's off. The algorithm just doesn't have any implementation of "when I'm off by a lot, I should make bigger jumps for a while". 

  • +1 over 1 year ago

    All,

    Please see our recently released beta software for a fix addressing this report. If you prefer to not install this beta software, we hope to be rolling out a public software update soon, though I do not have a timeline for this release. If you are still seeing this issue after installing the beta software, please contribute your observations in the appropriate beta bug reports section of the beta forums for your specific device.

    Enrolling in Garmin Beta Software Program