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How does Garmin compute VO2Max?

RVDowning
over 4 years ago

ow does Garmin compute VO2Max?  I mean the actual calculation, not an arm waving explanation about what it is, which is all that comes up when trying Google searches.

  • 0 over 4 years ago in reply to RVDowning
    RVDowning said:
    the difference I saw was that my max heart rate had increased

    Actually no it's not impossible. That is provided he really meant to say "the max heart rate you achieved had increased." Which can and does happen as people get better conditioned. It is unlikely to happen if you are already well-conditioned.

    I've said on many occasions here, VO2max is not a metric to be used to track acute changes in fitness/physiology. It is a chronic measure that should be visited over time say 8 to 12 weeks. If you are going to look at it very couple of days then plot the data over several weeks and look at the trend.

  • 0 over 4 years ago

    TL;DR it basically compares pace to HR and assumes there's a linear relationship, afaik. The faster you can run for a given % of your max HR, the better your VO2 Max will be. Personally I've always found that the Garmin-reported VO2Max is about 3 units too high (I have a 935), but the overall trend correlates with my fitness.

    Here's the FirstBeat technical white paper on VO2Max (not the marketing blurb). While some of the details (like filtering of bad data) may be proprietary, the basic concept seems pretty simple (and has been done elsewhere):

    https://assets.firstbeat.com/firstbeat/uploads/2017/06/white_paper_VO2max_30.6.2017.pdf

    My layman's understanding, based on the FirstBeat white paper, how other sites calculate VO2Max (such as https://runalyze.com), and various discussions here plus some internet sources.

    I apologize in advance for any errors here:

    • A linear relationship between HR and pace is assumed. e.g. If you can run at X km/h at 100 bpm, then at 150 bpm, you can run 1.5 * X km/h (I realize most people aren't running at 100 bpm, but I just picked really low numbers so the math is simpler).
    • Using the above assumption, your speed at max HR is extrapolated
    • By comparing your theoretical speed at max HR to other runners, your VO2Max (or some would say, VDOT), is determined

    I'm pretty sure the above is how Runalyze does things. There's also a few VDOT calculators that do the same thing. 

    I think what FirstBeat adds to the mix is:

    • Filtering of bad data (e.g. standing still)
    • Adjusting pace based on elevation grade (for watches with baro)
    • Adjusting VO2Max for heat (for newer watches)
    • Adjusting the race predictor for weekly mileage (for newer watches). The old Garmin race predictors just did a straight table lookup from VO2Max (or VDOT) to race prediction, similar to many race predictors on the web

    My understanding is that age, gender, and weight don't factor directly in to this calculation, although I could be wrong about that. But the simplest VDOT / equivalent race predictor calculators only ask how fast you can run a race of a given distance (or equivalently how fast you can run at a given HR, along with your max HR).

  • 0 over 4 years ago in reply to Former Member

    I didn't say HR changes, I said HRmax. Namely the one you put into GC. It can very well be that when you increase your HRmax in Garmin by say 20bpm, that your VO2Max shoots up after your next run by 5-10 points, same when lowering HRmax.

  • 0 over 4 years ago in reply to phl0w

    Well, there you go. If you have inacurate HR max, then obviously any algorithm relying on it will fail.

  • 0 over 4 years ago in reply to WillNorthYork
    WillNorthYork said:
    My understanding is that age, gender, and weight don't factor directly in to this calculation, although I could be wrong about that.

    I am no expert but Firstbeat/Garmin uses the Vo2 max formula mL/(kg·min) then I think weight will have some impact. I think if one will lower the bodyweight one might will have a higher Vo2max. I have read that Rower will not have the best Vo2max with the mL/(kg·min) formula due that they have much muscles and the weigh more, but if the use the other Vo2max formula (L/min) (without weight) they will have one of the highest vo2max readings. 

  • 0 over 4 years ago in reply to Messner

    I found this on the net, I dont know if it is correct. I my self lost about 2 kg (4 pounds) and my Garmin vo2max went from 43 to 44.

    "

    Hack 1 - Lose Some Weight

    This is first on the list because it is arguably the easiest way to increase your V02 max. You don’t even need to change your training all that much if you opt for this approach. The reason it works so well is actually pretty simple. 
     
    V02 Max is calculated relative to your body weight. The relationship is inversely proportional, which means the heavier you are, the lower your V02 max will be. 
     
    To illustrate this point, let’s pretend we have two athletes who use the same amount of oxygen during exercise, but weigh different amounts. 
     
    Athlete A V02 Max: 4860 ml of oxgyen/ 80 kg /1 minute = 60.76 V02 Max
    Athlete B V02 Max: 4860 ml of oxygen/ 90 kg /1 minute = 54 V02 Max
     
    In the example above it’s plain to see that Athlete A has the higher V02 Max, and this is precisely because Athlete A is lighter than athlete B, even though they are able to use the same amount of oxygen. " from https://5krunning.com/how-to-hack-your-v02-max/ and here is another intresting article https://www.runnersworld.com/health-injuries/a20817982/is-vo2max-proportional-to-weight/ but the intresting question is how Garmin/firstbeat calculate it. Maybe even garmin uses my bodyfat level, lean mass level from my Garmin scale to calculate? I dont think so.
  • 0 over 4 years ago in reply to Messner

    Yes, if you lose weight and all else is equal, then you can run faster at the same HR and your VO2Max will go up. That doesn’t mean that this algorithm uses your body weight directly to calculate VO2Max. Similarly, your speed may decline with age, which means your VO2Max will go down, but that doesn’t mean they need your age for the calculations.

    For example, there are online race predictors which will predict all your race paces and your VO2Max from the single data point of your 10K (or other distance) race time. They don’t need your age, gender or weight.

    As another analogy, you can use the “pinch test” to estimate your body fat percentage without knowing how much you weigh. 

    Another way of looking at it is it’s not measuring your VO2Max (nobody is measuring your oxygen intake), it’s estimating it from speed vs. HR data. So it’s not clear to me that it needs to take your weight into account. 

    The easiest way to test my hypothesis would be to change your weight dramatically in GC / your watch and see if your VO2Max changes dramatically (all other things being equal). 

  • 0 over 4 years ago in reply to WillNorthYork

    Also, Runalyze calculates a VO2Max for all of my runs, and it doesn't even know my age, gender, or weight. It only knows my max HR, and my pace/HR from my runs.

    The (uncorrected) numbers Runalyze gives me are pretty close to my Garmin VO2Max numbers. Runalyze does correct its VO2Max estimates based on past race results, which leads to pretty accurate race predictions for me (using the standard lookup table and another correction factor for marathons, based on long runs and mileage.)

    So it's def possible to calculate VO2Max based on speed and HR alone. I can't prove that's what FirstBeat does, unless I wanted to mess with all the physiological parameters on my GC account (and I don't want to do that.)

    ---

    For anyone who's curious, this is the procedure Runalyze uses to estimate VO2max from pace and HR:

    1) Takes your distance and time and calculates your VO2Max as if you ran a race, based on the Daniels/Gilbert formula (http://www.simpsonassociatesinc.com/runningmath1.htm)

    2) Corrects 1) based on HR (specifically, the average %HRmax of the run). The lower the %HRmax, the higher the corrected VO2Max. Note that if your max HR is set too high, your estimated VO2Max will be too high, just like FirstBeat.

    3) Applies a correction factor to 2) based on previous race results (how you actually performed vs. what was predicted)

  • 0 over 4 years ago in reply to philipshambrook

    No, he wasn't referring to the max heart rate I had achieved.  We actually had a discussion about this.

  • Former Member
    0 Former Member over 4 years ago in reply to RVDowning

    There's got to be some information missing here. You have 4 different HR zone profiles.  A general, running, cycling and swimming profile.  You can set up auto detect max HR, but you have to perform one of those activities for it to change.  Let's say you're paired to a power meter and have cycling VO2 Max of 42.  It will stay at 42 until your next ride with that meter.  It won't drop 8 pts to 34 because you took a couple of days off from cycling.  You said you took a couple of days off from running and it dropped 8 pts. Unless you went and changed some of your metrics, it's not going to to change until you do another VO2 Max qualifying activity.  I get it dropping 1 point after your next run because you said you had a change in HR Max, but if you didn't change anything prior to that run, then the 8 point drop while taking running off is an issue.