TL;DR: I got negative W’bal values but my calculated W’ is unchanged. How to adjust for this?
Looking at the profiles for my last race this part weekend I see that my W’bal went into the negative zone twice. See graph below. In the past when that happened the W’ value calculated in my power curve would change and I would update the number in my Power settings. This time however the calculated W’ value was unchanged. How do I adjust for this? Is this manual adjustment of W’ value in my settings the correct approach?
Your current W’ + the vale of your negative W’ value
From the above this would be 15.3 + 4.7 = 20k
The other alternative is to do a FTP test or similar to attain where you are at and a more accurate W’ - eg. could you of gone even harder/had a greater negative W’ value
Thank you both for the input. Yes, adding the portion that went below zero to my W’ works. In the past my W’ was automatically recalculated in the power curve when that happened, and I’d use that value. Did something change in the implementation or is this a weird power profile that happens to not update the model? Cheers.
I think you got to the root of the issue. My minimum duration in settings is 180s. This was a ~40min cyclocross race, with bursts of efforts, but it wasn’t sustained like a more traditional road race. My power curve for the season was updated in the 10-40min range due to this effort, but it didn’t update the eFTP.
Anyway, I was under the impression that the W’ calculation was based on my input FTP, not the eFTP, but it looks like I’m wrong. I guess there is a lot I don’t understand yet about how the W’ and W’bal are implemented in intervals.icu. Is there documentation anywhere that I can refer to?
I’m afraid I don’t have anything specific but this thread has lots of snippers of info in etc. including the algorithm that intervals.icu uses to calculate W’
This post from within the thread might also be useful…