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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 1 year ago in reply to 8300582

    About Runalyze - please read this to understand https://runalyze.com/help/article/vo2max

    It is your effective (not absolute) metric from last 30 days, not MAX.  If you run with a pace predication for a 10k, you get your VO2max  at 1st and 2nd Lap (average) (see "More details about your laps") very close to Garmins one.

  • 0 over 1 year ago in reply to 8300582

    My Garmin 255 believes my 10K race pace is 1:06. I jogged a 1:02 in zone 2 to give it a hint that it is wrong, but it would not listen. So I ran a 10K in 48 minutes to prove the watch wrong. But it still thinks my race pace would be 1:06! :-)

    It says my VO2Max is 49, which is "excellent" since I am 51 years old. But why does it think that I would run so slowly? After all, the VO2Max is based on my running.

    Maybe the age group Garmin refers to is the kind of people who would own a Garmin sport watch. Not the general population doing no exercise at all.

  • 0 over 1 year ago in reply to global_local

    I am very sure that you interpret this wrong. It's called 'VO2max' because it is your MAXIMUM oxygen processing capability, calculated by your pace, distance and HR. That's why it needs your HR: It determines your Max by looking how far your HR is below your max HR. It's not your oxygen consumption per minute (which would be your interpretation of this text).

    "Current" and "effective" refer to this value not representing your all time best, but instead the 30 day average of what you can actually use while running.

    @ovekvam: Your age should only be used for telling how your your VO2 max is, not for your race predictions. How long do you use your Garmin for? Give us some more info about the problem :) 

  • 0 over 1 year ago in reply to ovekvam

    @ovekvam are you absolutely sure your max HR is set correctly? It sounds like you should probably set it significantly higher. What were your HR zones during your fast 10k run? and what was your perceived effort of that activity? was it your maximum effort?

  • 0 over 1 year ago in reply to angainor

    Zone 1: 60-72%
    Zone 2: 72-82%

    Zone 3: 82-87%

    Zone 4: 87-92%

    Zone 5: 92-97%
    These zones are very popular in Norway.

    My 48 minute 10K was a zone 4 run, pretty much all in.

    I have had the 255 for just over a month, but had a Vivoactive 4 before it, which has been indicating the same VO2Max, which I think sounds reasonable. I just don't understand the race prediction.

  • 0 over 1 year ago in reply to ovekvam

    Your zones look fine, if not a bit aggressive for my taste. Zone5 should probably end at 100%, unless you also have a zone 6 ;P But if you were in Zone 4, then my guess about your HR must have been wrong. Maybe you just need to run a bit more to let the watch make a better model. All I can say is that my prediction is more or less spot on. I run 3 years now with a Garmin FR945.

  • 0 over 1 year ago in reply to ovekvam

    You could check some online ressources about the race predictions with a VO2 Max of 49. Do they rather match the Garmin predictions or rather your real capabilities?

    And do you have your max heartrate set correctly (meaning: Set to your real max HR, not some formula).

  • 0 over 1 year ago in reply to ThePhoenixCoding

    My max heartrate is based on experience, not a formula.

  • 0 over 1 year ago in reply to ThePhoenixCoding
    ThePhoenixCoding said:
    VO2 MAX is mostly dependent on your training status and not on your genetics

    Yes - "mostly". But the range 20-50 or 30-90 refers to your genes. So i would count both metrics. For ones is easy  to increase from 45 to 50 in 2 week, for the other it is impossible at all.

    "I am very sure that you interpret this wrong." Ahmm. I can only read the linked text to runalyzes calculating method. I interprets nothing.

    Garmin makes predication, runalyse makes it too. But did it in other way. That was my only focus.

  • 0 over 1 year ago in reply to ovekvam

    What activity class are you set in Garmin Connect? How many active minutes have you do per week? It have impact on race prediction too.