Estimate based on heart rate and speed at the basics. Probably as accurate as a field FTP test on the bike or other field tests for zones and fitness.
https://www.firstbeat.com/...2max_11-11-20142.pdf

If you want accuracy, go for a real sports testing facility or lab (and bring your credit card - $$$$).

If you want something to give you some markers over time to get relatively improvement, it works.

---

Ryan
http://www.SetThePaceTriathlon.com
http://www.TriathlonTrainingDaddy.com
I got plans - https://www.trainingpeaks.com/...dotcom#trainingplans

In case this is helpful insight for anyone, I had found for a long time that my Garmin's estimate of my Vo2max would go up when i trained hard or raced, and would consistently fall whenever I would take easy days. Now, these would be short periods of rest, so i knew my *real* fitness wasn't changing, i figured it was just about the calibration or whatever. As a result, the training status metric would literally ALWAYS say "unproductive" after an easy day.

Well, I also had started using an HRV app to monitor recovery, and my HRV is usually super low; even when i'm rested, the population comparison histogram has me in the bottom tail of the distribution, even though resting heart rate is right smack dab in the middle of it.

And i still don't know why this is, but probably not coincidentally, I was diagnosed last year with an anxiety disorder.

So I am wondering if my high stress levels and associated low HRV "fool" the VO2max machine into thinking that I am actually nearer to my max than i actually am when i am riding easy, in other words, because the HRV difference (for me anyway) between easy pace and hard pace are actually not as different as they are "supposed" to be. If so, then be aware that there are even MORE things that can confound the accuracy of the measurements!

If it were just about accuracy of the VO2Max calculator, i'd say "f*ck it whatevr" and forget all about this, but given that this is also potentially an indicator of general lack of psychological well being (which, of course, affects recovery, training, happiness, etc.), i'm going to try to see what i can do to fix this, starting with meditation.

Has anyone else tried meditation and had it work?

From my experience, the accuracy is associated to how carefully you parameter your heart info.

Correctly parametered, bike VO2max estimate (with power meter) is for me within 3% from extensive lab test.

But if you missed the BPM info (max, levels), then of course, it fail.

Ideally, you do an extensive test, and you use the detailed info obtained to correctly parameter the 935. Then you have a correct view of that variations.

Of course, reference of the system to heart rate mean it is sensitive to variation. If you do gut training for example, your stomach or intestine working, it elevate HR, the lower VO2 estimate, ...

Hey all,

Question on how to interpret the Fenix 5 data that i'm wondering if anyone here can help me with.

I have found that the Vo2Max estimation that my Garmin gives me is much lower when i exercise at lower intensities than when i exercise at higher intensities, to the tune of 7 or 8 ml. In other words, when i try to do a long zone 2 ride or recovery ride it tells me my vo2max is falling whereas when i go out and do zone 4 intervals or higher, it tells me it's rising. This is irrespective of fatigue or time of year or whatever.

I'm not super concerned with how accurate the estimate is (who really cares if that's actually my Vo2Max??) but rather how to interpret this relationship.

Would this mean that my aerobic fitness isn't that great relative to my ability to punch out some power anaerobically?

If that's the case, how do you all address aerobic fitness as a weak point? Just go out and do Zone 2 until heart rate starts to drift, and measure fitness improvements by how long it takes until that happens / how much power you can produce at the same HR?

thanks!

Maybe you set the Max HR too high in the watch ?
Then, the more you push, the more it will typically over estimate the VO2

It's a fair question but after double-checking i don't think that's it. I just double checked the setting, and my max HR for running is set at 205 and my max HR for cycling is set at 199, and the maximum I observed in each sport last year was 204 and 198 respectively, so if it's off it's not dramatically off

OK

If you spin a lot in recovery ride, it will push HR higher than needed
Same if you eat just before easy ride (probably not for zone 4 workout) it will push HR higher
In both cases it will fool the soft and lower VO2 estimate.

Or your rest HR is set too low (not sure it is used for estimates) ?

I started training for IMTX a few months back. The majority of my volume is lower intensity. I've watched my 935xt VO2max drop steadily the past few months. It's just now starting to bump back up. But generally speaking I'm seeing the same thing - my Garmin VO2max is highest when I'm doing higher intensity workouts on a consistent basis. While it jacks with me mentally to see numbers drop (other than weight) I'm not really putting a lot of stock into it.

Got it, thanks, you're probably right about the spin.

Thanks for hte input!

I'm not necessarily putting stock in it either--as i said, i don't really care if it's accurate. But, it means something, right? Either this is telling you something real about your physiology, OR it's some kind of quirk of the machine, OR it's getting confused by some kind of noise (for example, if you do low intensity work indoors where it's hotter, high intensity work outdoors where it's cooler)

I'm just curious what it is that is causing this relationship! I'm not sure Garmin or FirstBeat publishes enough of the secret sauce to really tease it out, which is too bad

I did a v02 max test (cycling) in the lab today and my result was 7.5% higher than what my garmin 820 says. Garmin was much closer than the typical formula approach with 20 minute wattage x 10.8/weight +7, so I give the Garmin pretty good marks. The formula was about 14% low compared to lab.

There is no real way a garmin can know actual v02max because it has no idea what a person's efficiency is, so whatever algorithm they use has to be based on a bunch of "middle of the road" assumptions. My read on the difference between the numbers is that I'm probably a little less efficient than the average person and that's why the garmin is low compared to the lab.

I've been wanting to do a vo2max test for years, but there just isn't a whole lot of real value in the number from my perspective. That said, I'm a big numbers geek and my curiosity finally got the best of me and it was cool experience and well worth the $.

The first beat algorithms are probably done with a 95% confidence interval that I assume is wide. My runnin vO2 max is 65 and it claims I can run a 2:32 marathon which is rich. It has my cycling one at 72. What?

Yeah, mine is WAAAAY off.

Initially, it was absurdly low, for several months.
Started creeping up, but still well below where V.Dot run paces would suggest my actual # was.

Example - it was stating my estimated 5k race pace was like 22 minutes.
Even tho I had recently done a 3m tempo run in 19 flat. 🤔
(I guess it assumed I’d be crawling the last 0.1 mile)

Then, I got sick of the random # generator (aka optical wrist HR) and started using my chest strap to get non-garbage HR #’s.

Once I did that, my “G.Dot” skyrocketed.
Got as high as 62, which was wildly entertaining when looking at the estimated paces for 5k thru Mary.

It then dipped precipitously - which was slightly closer to actual, tho still way too high.

Then it inched up another tick or 2, to a G.Dot of 59 currently.

Now, 7 years ago when I was coming off a big block of training, and had built up to my lifetime best bike & run fitness, that wouldn’t have been wrong.

But I ‘know’ based on my current run paces, relative lack of run training compared to then, etc that my best case currently is a V.Dot of maybe 54. Maybe.

Oh, and it says my cycling G.Dot is 64.
LOL. 🤪

---

float , hammer , and jog

I have a forerunner 235 and the wrist heart rate monitor function seems super-inaccurate. Sometimes I am going all out and it reads 130bpm, sometimes I'm jogging and it reads 200bpm. As the algorithm used heart rate data, this means the estimate of vo2max varies by 20%+ week to week so I just ignore it. Highest reading 60 lowest reading 44 and guess the truth is somewhere in the middle.