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larkim
larkim
Jan 2021
8:21am, 13 Jan 2021
13,205 posts
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larkim
With respect to Fetch, I think he's using a calculator there which isn't really fit for generalised purposes. The study it is derived from gives a margin of +/-5.6 in the results (which is pretty huge in VO2Max terms) and is specifically designed only to report VO2Max predictions from very easy runs (the idea of the study was to get a method for estimating VO2Max for people who were unfit and being medically encouraged to take up exercise).

For me that calculator gives me an answer about 6 or 7 higher than the "VO2max from PB" calculators would suggest; and my understanding is that that concept of VO2Max being closely aligned to PBs is pretty solid science (though I could be wrong and the margin of error could be high there too).
SteveC NordRunner
SteveC NordRunner
Jan 2021
8:25am, 13 Jan 2021
388 posts
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SteveC NordRunner
Is 5.6 one SD, Larkim?
larkim
larkim
Jan 2021
8:30am, 13 Jan 2021
13,206 posts
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larkim
Now you're asking stats questions that I can't answer!!
larkim
larkim
Jan 2021
8:34am, 13 Jan 2021
13,207 posts
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larkim
The graph on page 9 of the paper tandfonline.com visually tells the same story though - definitely a good data set, but the upper and lower bounds of the results suggest to me that for some (many?) people the margin of error could be quite large vs the formulaic output.

There's no way I have a VO2Max in the 60s; but equally I don't think my HR and easy pace runs speed for my age are particularly out of the ordinary.
SteveC NordRunner
SteveC NordRunner
Jan 2021
9:13am, 13 Jan 2021
389 posts
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SteveC NordRunner
Well, the SEE for the regression line is 2.52. Let's call that 2.5. The 95% confidence interval is always 1.96 SEE either side of the regression line. Let's call that 2. So let's say the regression equation gives you a personal result of 55. The 95% confidence interval for that result is from 50 to 60.
larkim
larkim
Jan 2021
12:28pm, 13 Jan 2021
13,211 posts
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larkim
That makes sense and ties up with the 5.6 +/- (ish). The thing is, a VO2max of 50 represents a 20:00 5k runner, a 60 represents a 17:03 5k runner; that's quite a big gap if the numbers are to be used with any relevance for people who's hobby is running / running performance.

For anyone getting a result which seems consistent, I'd suggest looking up what that means in terms of race pace (best route is the VDOT tables in the Jack Daniels publications, which can be seen online). If the fetch calculator suggests you are a 18:30 5k runner but your lifetime PB when well trained is 21:00 then I'd say that even if the fetch calculator is in line with some other data from a garmin etc, it's still a rubbish number. Or you are massively underperfoming as a runner!

The "Garmin number" for me at the moment is about 57.5. Even that is too high compared to my capability when well trained (55-56 is where I'd be based on my well trained 5k PB), but I get the sense that the Garmin number does tend to be a bit on the generous side anyway. Though if I track the Garmin calc over a period of time it does do a good job of reflecting a perceived improvement in fitness, especially when viewed to a couple of decimal places (via RunAlyze); but even so, it doesn't vary by more than 2 or 3 points.
SPR
SPR
Jan 2021
12:44pm, 13 Jan 2021
32,931 posts
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SPR
I think what you say about how the number is then used is the main point Larkim.

Garmin number is used differently now on new watches and give less generous predictions than a VDOT table would. That doesn't work well for me, but seems to work well for others. The previous method had better predictions for me TBH, but I don't know how well the VO2 max number I get is calculated (highest I've seen is 64 or maybe a brief period at 65 this year).
Dvorak
Dvorak
Jan 2021
1:47pm, 13 Jan 2021
21,738 posts
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Dvorak
My Fetch number is around 44.5, my Garmin number is currently 41 (has been between 40-42 since I got the watch, but with cycling readings of 43/44) and my VDot is 27.
larkim
larkim
Jan 2021
1:57pm, 13 Jan 2021
13,217 posts
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larkim
That's a huge gap Dvorak. Are you just sandbagging in races ;-)

VDot could be low vs lab tested figures if you weren't perfectly trained for a PB performance, so it's not impossible that your real VDot is higher than 27, but I thought mine was way off with a gap of 6 or 7; 13-15 is enormous!
SPR
SPR
Jan 2021
2:03pm, 13 Jan 2021
32,932 posts
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SPR
VDOT just measures running performance though so can't really be 'wrong', you just may have the potential to increase it.

That assumes the Garmin has all the right numbers to calculate your VO2 Max correctly.

About This Thread

Maintained by Elderberry
Everything you need to know about training with a heart rate monitor. Remember the motto "I can maintain a fast pace over the race distance because I am an Endurance God". Mind the trap door....

Gobi lurks here, but for his advice you must first speak his name. Ask and you shall receive.

A quote:

"The area between the top of the aerobic threshold and anaerobic threshold is somewhat of a no mans land of fitness. It is a mix of aerobic and anaerobic states. For the amount of effort the athlete puts forth, not a whole lot of fitness is produced. It does not train the aerobic or anaerobic energy system to a high degree. This area does have its place in training; it is just not in base season. Unfortunately this area is where I find a lot of athletes spending the majority of their seasons, which retards aerobic development. The athletes heart rate shoots up to this zone with little power or speed being produced when it gets there." Matt Russ, US International Coach
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