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VO2 Max and FTP comparisons

Perusing the manual http://static.garmin.com/pumac/Forerunner935_OM_EN.pdf
then the VO2 Max and FTP tables are interesting.

On Zwift you are in the top category over 4 W/kg. Here that is only good enough for Excellent and Superior starts at 5.05 W/kg which I view as very "Superior"! Not many Zwift racers can manage that...

On the other hand for VO2 Max "Excellent" is only 51.1 and even Superior is still a relatively modest 55.4

My last FTP test put me a shade over 4 W/kg (293W, 71 kg) and yet my VO2 Max on the 935 for cycling is 59 and running is 60. VO2 Max values from the Firstbeat algorithms tend to be a little flattering but I am certainly well over 55 on race predictions for sure.

So perhaps a bit of a conflict here between these two tables? Either that or I need to be pushing out a good 50 more watts!!!

0 ASmugDill over 8 years ago

I wish there was a better explanation than "you have to artificially adjust your MaxHR down".

Personally I'd advocate pretending that the Race Predictor is worthless for now, and focus on establishing whether the VO[sub]2[/sub]max estimates are “within the ballpark” when compared against results from proper lab tests for VO[sub]2[/sub]max. As far as I'm concerned as a user (both of Garmin fitness devices and of VO[sub]2[/sub]max estimates), that figure is a measure of aerobic fitness first and foremost.

I'd be delighted if the VO[sub]2[/sub]max estimates are reasonably accurate, while the “gross deviations” are primarily in drawing invalid inferences from such to project race completion times in Race Predictor because it fails to account for too many other relevant factors. The FR735XT Owner's Manual says,

Your device uses the VO2 max. estimate (About VO2 Max. Estimates) and published data sources to provide a target race time based on your current state of fitness. This projection also presumes you have completed the proper training for the race.

and,

VO2 max. data and analysis is provided with permission from The Cooper Institute®. For more information, see the appendix (VO2 Max. Standard Ratings), and go to www.CooperInstitute.org.

I had a look on the Cooper Institute web site, but I didn't see anything outlining the mathematical/functional relationship between VO[sub]2[/sub]max and race completion times, such that the latter can be expressed as formulae using the former as the primary variable. There is some stuff on the inverse relationship, i.e. estimating VO[sub]2[/sub]max from actual performance in the ‘beep test’ or the One-Mile Run, PACER and One-Mile Walk tests, but even there the information seems to only pertain to (or have been statistically derived from data gathered from) younger individuals.

0 Olu.F. over 8 years ago

Definitely take the race predictions with a grain of salt.

Think of the race predictions as the what you could do if you were in peak condition, optimal AGE and training for that specific distance.

No one can be in peak condition at all distances at the same time. Shorter faster races are better for younger runners (and life long runners).

I'm not young (47 years) and started running later in life. I would have a difficult time hitting my current 5K prediction of 18:48. However the half-marathon prediction of 1:26:18 is well within reach at my current fitness level.

0 R_Tellis over 8 years ago

The Race Predictions are from the Daniels VDOT chart, so if your VO2max estimate from the watch is off by more than a couple of points then the predictions will be unrealistic.

There was a thread awhile back on here in one of the other Forerunner threads where most people seemed to agree that they were getting a VO2max from their watches that was about two steps higher than where their actual times fell on the VDOT chart. Which was pretty close for me at the time as well.

0 webvan over 8 years ago

It's not exactly VDOT if you look at http://runsmartproject.com/calculator/ but about 1.5 points higher for similar predictions

VO2Max 56 ~ VDOT 54.7
5k : 18'26/18'27
10k : 38'14/38'16
HM : 1h24'34/1h24'40
M : 2h56'32/2h56'44

@KALAMARIOS - How far off are you prediction wise for the Marathon ? Have you entererd a recent "fit" HRMax ?

0 timgrose over 8 years ago

> @KALAMARIOS - How far off are you prediction wise for the Marathon ? Have you entererd a recent "fit" HRMax ?

Yes was going to ask similar and what are your other PBs?
The marathon is probably of the hardest of those distances to "get right" as you
(a) Have to be doing the miles for it
(b) Are naturally suited to the distance (and many aren't)
(c) Things go right on the day for you and the weather
(d) Course is fast

0 kalamarios over 8 years ago

> @KALAMARIOS - How far off are you prediction wise for the Marathon ? Have you entererd a recent "fit" HRMax ?

Yes was going to ask similar and what are your other PBs?
The marathon is probably of the hardest of those distances to "get right" as you
(a) Have to be doing the miles for it
(b) Are naturally suited to the distance (and many aren't)
(c) Things go right on the day for you and the weather
(d) Course is fast

My PRs are:
Half-Marathon, 1:24:18, Jan 2015
Marathon, 2:58:46, Dec 2014

My two most recent races are:
Half-Marathon, 1:24:45, Jan 2017
Marathon, 3:03:03 (yup that happened), Dec 2016

My current VO2max estimate (according to my 735xt) is 64(!) and my "fit" HRmax (according to HRM-Run) is 189 from Jan 2017. I hit 186-188 almost every other week during hard intervals.

I am running the Boston Marathon in 9 days and who knows, maybe I will run a 2:34 (the current 735xt race prediction for VO2max 64). Then I will shut the hell up, give my 735xt a kiss and frame it on the wall! ;-)

0 kalamarios over 8 years ago

I did some further reading on the FirstBeat whitepapers. One plot specifically stood out that I would like to share with everyone.
https://assets.firstbeat.com/firstbeat/uploads/2015/10/white_paper_VO2max_11-11-20142.pdf

First to quote the text (bottom of page 4):
"Because the Firstbeat method is sub-maximal by nature, it uses an age-based estimated maximum heart rate (HRmax) in the calculation. Therefore, the error in the HRmax estimation affects the accuracy of the VO2max estimate. Figure 5 shows how much the difference between a person's actual and age- based HRmax affects the VO2max estimation error in the mentioned database of 2690 freely performed workouts. If the HRmax is estimated 15 beats/min too low, the error in the VO2max result is about 9%. Respectively, if the HRmax is estimated 15 beats/min too high, the error in VO2max result is 7%. If the person's real HRmax is known, the VO2max assessment error falls to the 5% level."

And here is the plot (bottom of page 4)

So as you can see, the VO2max estimation error is asymmetric around the ground truth. Specifically the error is larger if you underestimate your HRmax (up to 9%) than if you overestimate it (up to 7%). In that sense, the advice to set your HRmax to a lower value (if you want your VO2max to be more "realistic") actually introduces more error from the ground truth VO2max than if you accidentally set it to a higher value.

What do you guys think?

0 timgrose over 8 years ago

Well the age based estimate is the default max HR that the watches are set during the setup wizard. 220-Age. So that makes sense. A lot of people never change that.

Clearly though if you set it to a different value then it uses that.

If you set the max HR too high you get too high V02 Max and too low HR you get a too low VO2 Max which is basically what been advising everybody for some years. The actual percentage error is largely only of passing interest.

And, for me, it's not about artificially lowering my max HR to get a better VO2 Max, it is about setting max HR to a value I can actually get to (or very close) at the moment as my attainable HR does seem to have some correlation to my fitness - fitter I am harder it is to get it high.

So why is your one seemingly about 5 or 6 points too high...

Your HM & marathon times are in broad agreement with perhaps the HM being very slightly better.
But what your are 5K and 10K times? Those distances are more relevant to the ability to perform well in actual VO2 Max tests.

Then there is the question of your threshold HR and your pace at it?

Logically the high VO2 Max suggests you are a lot better at shorter distances than long ones.

It is also interesting that you can so regularly get so close to your max HR. I can't. What sessions are you typically doing to achieve that?

0 webvan over 8 years ago

Yes as we've found the VO2Max calculation is indeed based on the HRMax you enter into the watch so while interesting the Firstbeat papers you mention don't apply here unless you haven't changed the default settings? If you haven't what's the value shown?

Like Tim there's no way I can get close to my actual HRMax of about 180 measured before I started endurance training 3 years ago these days with regular marathon training. I'd say 170/172 would be the max on hard sessions like Daniels' IPace.

0 ASmugDill over 8 years ago

It's not exactly VDOT if you look at http://runsmartproject.com/calculator/ but about 1.5 points higher for similar predictions

Heh… my FR630 tells me my VO[sub]2[/sub]max is close to 48, whereas given my one-mile and 5K personal records as input, the calculator above tells me my‑VDOT⋍38.

… continue to tweak the MaxHR so that the actual estimates are better. That's a problem for me.

And on, and on, and on…

What do you guys think?

OK, you did ask. What's the big frolicking deal about the VO[sub]2[/sub]max estimate by a consumer fitness device not being as reliable as you'd like? If you really want an accurate assessment, then by all means, have a lab test done.

I understand your imminent participation in the Boston Marathon is a big deal to you. What your watch tells you ahead of it shouldn't be, though.