Apologies if this has been requested already, couldn’t find it.
Runalyze has effective vo2max which determines race prediction on a day by day basis, taking into account how more or less fit I am over a season. It works well.
Can something similar be done here? I feel that it would be more accurate because intervals.icu is using my LTHR, which I keep up to date, and also considers resting HR.
So does it use that to predict your time for 5k or 10k or whatever?
Yes - any arbitrary distance which is what makes it cool. This is how it works:
effective vo2max is essentially the closest fit line of all your runs’ “performance” (eg, avg pace combined with avg HR, at its simplest). The fit line itself can be personalised with a correction factor, as you can see it fits very well my recent races/time trials (bigger circles on the right-hand side of the curve) and since my season ended, effective vo2max is going down (currently estimated at 42.9)
effective vo2max is equivalent to “VDOT”, so that’s how race prediction is calculated:
Hopefully this helps!
Tx for all this.I have creating a “pace vs distance” chart on the todo list (same as power duration curve basically). With any luck power models will work for this then it will answer best time for x distance.
Awesome, can’t wait to try them 
Here’s a nice collection of running race predictors Other distance race time predictor
Polar also does basically the same thing as @fabio.ticconi described:
They call it “Running Index”, but it’s just a vo2max prediction based on chunks of running longer than 12min where speed stays above 6km/h (but I remember reading that a couple of stoplights are also allowed). Anyway, it’s not terribly effective. On the plot above, the best predictions for 5k and HM are 18:50 and 1:26:30. I’ve run 17:00 and 1:18:20 this year.
In my experience, race times prediction works best when comparing real races. E.g. 5k <> HM conversion usually works for me up to few %
I’ve come across this article, showing the hyperbolic relationship between time & pace for different race lengths (best efforts): A Big Data Approach to Predicting Your Marathon Pace - Outside Online
The neat thing is that the corresponding **time-vs-distance plot is linear ** - and the slope of the line would be the CS in m/s. So it’s very easy to find.
Critical speed is important, because it’s the theoretical limit one could run “forever” - and one could even try to use it predict marathon time (better trained runners can use a higher % of their CS). I suspect Runalyze (and Polar) are using something like this for their “effective vo2max” / “running index”.
Might be of use maybe? A Critical Speed calculator taking in best efforts (three distances chosen by user?) in a certain date range would be neat, although it wouldn’t be a moving average (eg, would not represent your daily race readiness, but your season’s or all-time CS).
You might find this useful for calculating your critical speed. I’d add a word of caution when using CS for predicting anything above about 10k though for us amateurs.
Hey that’s very cool - it seems like I was already registered though, and forgot the password. There’s no password reset mechanism, I feel like that is pretty important to implement 
Is there a support email I can write to, to get it reset?
Yeah something I’m going to fix in 2022! Email me at john@endura.fit and I’ll reset for you.
Just reviving this thread to let folks know there is still interest! Critical Speed is really bad at predictions if you have faster times in shorter distances. For example I’ve run a 5k at 6:03 pace, and because my 2mi record was also set during that run at ~6:01 pace, CS R2=0.9999 thinks I can run a half marathon at 6:06 pace, whereas Vdot would predict 6:35 pace which is obviously more reasonable.
Yeah, I think power law should be an alternative. Essentially finding your own individual riegel exponent
Or just implement Vdot 
I ran a 5K 2 weeks before a HM, both all-out, and vdot predicted my performance on the HM within one second. I didn’t believe I could run it and started much more conservatively, but negative split to a 1:23:54 which was a good HM debut for me.
t2 = t1 × (d2 / d1)^b could work if you try to estimate what the exponent is for the person (I definitely think the riegel b=1.06 is too aggressive for me.
Vdot calculation is this, for reference if anyone looks later!
VO2 Max = (−4.60 + 0.182258 × S + 0.000104 × S2)/(0.8 + 0.1894393 × e(-0.012778 × T) + 0.2989558 × e(−0.1932605 × T))
where:
S is speed in metres per second
T is time in seconds
My understanding is that to predict a different time based on this, one then best-fits several different times for the pre-set distance to approximate the S where the V02 max matches the athlete’s Vo2 max. Complicated, but extremely effective I’ve found! It’s how I set all my running paces and has led to success for me including PRs at 1mi, 5k, and HM for me in the past 3 1/2 months of racing.
Congratulations on the PRs! 
A couple of months ago I was intrigued about the VDOT system and how Daniels’ paces come to be. It’s not that complicated and revolves around the two equations you shared. I created a notebook that tries to be comprehensive about the mathematics/approach.
The “official calculator” is most likely using a more sophisticated approach (particularly for the lower ranges of VDOT). After all, those equations are based on a book from 1979. 
please don’t let this thread die lol!
as i go deeper on running i really miss the intelligence of the bike metrics for evaluation and updates for training zones. as power is kind of a messy subject on running, there are plenty and very simple calculations based on paces that would save people a lot of time, specifically:
from there, would be nice to have things like:
