Trust Garmin VO2Max & Race Predictor?

I do not pay attention to it. Seems to come and go with accuracy relative to my current race times.

Mine is hilariously inaccurate. A few months ago, I ran a half-marathon (on a certified, record eligible course with no net drop) in 1:26. Garmin updated my projected race times to 1:28 for the half.

Some time later, I ran a 5K in 18:51. Again, accurate course, no net drop. Based on that, Garmin predicted a mid-19 5K.

My Garmin has absolutely no faith in me.

The Garmin VO2Max stuff is partially based on Heart Rate Variability. This was a hot topic in cardiology research 10 years ago, but has been much been abandoned as there are few clinically significant uses for the metric.

A 5k race is going to be a much more accurate predictor of VO2Max then a heart rate monitor.

As benski indicated, heart rate variability (HRV) is a part of the Garmin estimates for VO2 and VO2max. Garmin licenses technology from Firstbeat, a Finnish company ( https://www.firstbeat.com/en/ ). One of the validation studies on Firstbeat HRV technology estimated VO2max at ~ 6%, which is very good for these devices. However, as you can figure, if you are off by that much in your time for a race, that is disappointing for most serious runners. If the devices are reliable, even though they have error (the error is consistently the same), deviations from 'normal' over time may help identify something important. But on a single prediction, a race time, there is too much error for it to accurately get your time right, not to mention weather and terrain.

darkwave wrote:

Mine is hilariously inaccurate. A few months ago, I ran a half-marathon (on a certified, record eligible course with no net drop) in 1:26. Garmin updated my projected race times to 1:28 for the half.

Some time later, I ran a 5K in 18:51. Again, accurate course, no net drop. Based on that, Garmin predicted a mid-19 5K.

My Garmin has absolutely no faith in me.

That is funny, cause it is exactly opposite for me. I've run two 5ks recently on certified courses. 19:05 and 19:11. My Garmin tells me i can run 18:04.......I WISH!!!! And it has even at one point in the last month told me I could run 17:48......and yes i was running at my limit for those 5ks.

I would trust a 2 mile time trial over the watch any day.

If you want to estimate your vo2max, try this:

-Run as far as you can in 15 minutes and accurately record the distance.

-convert distance to meters (1609m per mile)

-divide total meters by 15 to get meters per minute

-the first 150m/min is equal to 33.3 mg/kg/min

-for every meter over the base of 150, multiply by .178 and add to the 33.3 mg/kg/min.

-for every meter under the base of 150, multiply by .178 and subtract from the base 33.3

Example:

Runner runs 4800m in 15min

4800/15=320

320-150=170

170*.178=30.26

33.3+30.26= vo2max of 63.56 mg/kg/min

It says my VO2 max is 68 and my race times is 15:17 for 5K.

Maybe the VO2 max is right but it usually means nothing. Because my 5K PR is only 16:46. Maybe I have horrible running economy or clear lactic acid very inefficiently?

It said my vo2max was 51, and predicted a 3:10 marathon.

I ended up running 2:58.

And it says my half marathon prediction is 1:10. I ran a 1:21.

Predicted marathon time 2:42, ran 2:56, and I am an mid 40ies hobbyjogger who does substantially better at long distance 10k upwards.

Whatever garmin uses for it's calculations for VO2max, performance condition, training load (sum of epoc) includes pace per mile. I run a lot on singletrack and it gives me super slow predictions.

All GPS watches can't come close to accurately measuring tight, wooded singletrack. My heart rate was 160 for 40min but I was running 9min/mile. Must be because my VO2max dropped 5 points overnight. If I hit one solid fast pace run on straight roads, everything shoots right back up like I became a superstar overnight.

So my experience, it might be much closer if you run dirt roads, asphalt roads that are straight. If you run trail or mountain, you are better off keeping the screens at HR and time of run.

John Clendon wrote:

So my experience, it might be much closer if you run dirt roads, asphalt roads that are straight. If you run trail or mountain, you are better off keeping the screens at HR and time of run.

true, while the issue here is not so much winding roads but incorrect treatment of uphill/downhill. For calculation puporses, algorithms translate this typically by lengthening distance by a certain factor which has nothing to do with reality.

Always predicts much faster than my current times and level of fitness. I don't pay much attention to it. The times it is showing right now are times I am capable of if in a higher state of fitness, but definitely not today as I've been injured and only now able to run and train with some consistency for the past couple of weeks.

Guess it would be good to be able to apply some custom weighting to it, like from your PRs, age, etc.

Isn't the biggest problem that it assumes a simple, mechanistic relationship between VO2Max and running speed?

Little Guy Garmin wrote:

Always predicts much faster than my current times and level of fitness. I don't pay much attention to it. The times it is showing right now are times I am capable of if in a higher state of fitness, but definitely not today as I've been injured and only now able to run and train with some consistency for the past couple of weeks.

Guess it would be good to be able to apply some custom weighting to it, like from your PRs, age, etc.

Seems like I'm the only one who is given predictions that I'm not sure I could achieve. Mine are so much faster than my PR's.

That sounds pretty accurate to me. What do you expect? It's a just a watch.

I am in the camp where my Garmin Race Predictor is WAY faster than my actual PR's. VO2 Max 64, 42 year old hobby runner trying to go sub-3 at Chicago and then hopefully get