Negative W'ball and how to adjust

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?

just click the pencil icon next to W’Bal at the workout summary and input the new number.

yes. for now it is

Which new number? My W’ is unchanged.

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

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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.

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The W’ is only updated in the power curve when a new eFTP is detected I believe.

As such, the effort you did to achieve the negative W’ probably was not long enough to qualify as triggering a change in your detected eFTP.

What is your ‘minimum eFTP duration’ in Setting set as and what was the duration of the effort above?

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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 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 uses to calculate W’

This post from within the thread might also be useful…

Caveat: info might be outdated…

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