How is W'bal replenishment rate calculated?

1

I’ve been using the W’bal chart on my rides and it seems to be pretty accurate in terms of when I dig deep and empty the tank.

What I’m less sure about is the replenishment rate? How is that calculated? Surely it will be different for everyone? Is there a way to “personalise” it? e.g. We all know younger people seem to “recover” more quickly from intense efforts.

Just interested to know. I couldn’t find anything about it.

2

check the thread. The entire code is actually provided by David

3

I’ve read that entire thread and seen the JavaScript code before posting.

I couldn’t find the replenishment formula in it, hence my question.

4

let deltaW = cp - data[i]
if (deltaW > 0) {
for (let j = 0; j < secs; j++) wb += deltaW * (wPrime - wb) / wPrime
} else {Preformatted text
wb += deltaW * secs
}

The key is basically these

when current power > cp, then wPrime gets depleted. When power < cp then wPrime gets replenish.

HTH…

edit: the replenishment rate is based on time and power below CP. There are 2 methods of calculating… integral vs differential.)

intervals uses the differential algorithm and that’s also what I use in my BreakAway: Indoor Training App

3 Likes
5

OK I think I get it now. Thanks.
So for each second below cp, W’bal is increased by…

deltaW * (wPrime - wb) / wPrime

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6

Slightly related question… I took my CP and W’ parameters from the intervals.icu estimates but they are clearly wrong because my W’Bal repeatedly goes negative even though I am no where near my limit. Is there a way for intervals.icu to automatically update its estimates when the W’Bal goes negative?

7

currently not yet. it’s in david’s todo list… for now, you do it manually

8

Any suggestions on how best to do that? Increase CP or W’ or both?

9

on a ride which you see the -ve value, then it’s time to change your W’ number. Either in the /SETTINGS page or within the specific activity (and it will carry forward for future)

10

Why W’ and not CP?

11

I’ve found the w’bal from zwiftracing.app to be pretty close, but I suppose it does depend on the data it gets fed from your racing results. (All this assumes Zwift and Zwift racing though).

12

Yes it could also be that your CP needs a tweak if you’re regularly going negative on w’bal