Hi there.
I have just done a workout where my W’bal is over max amount.
I can max set 60000j in here but after race tonight I says I’m -14.2kj. Max amount 74.2kj.
How can I set it to show my true max?
//Christian
You can change it on your settings page.
70k w’bal is a huge amount…what does it say your w’bal is for 90d on your power page?
Not sure how this works then.
If I’m under 20kj, why is my race then telling me I’m using 74kj?
Then I’m pretty much riding at 400% capacity??
w’ is not the whole work you can perform during a workout or activity, but, simply speaking, the maximum anaerobic work that you can perform over your critical power (CP), if your power output is constantly above that CP. For example, if your CP is 200 w and you output 220w for 1 min, your comsumption of w’ will be (220 - 200)·60=1200J
Moreover, w’ models consider that if you come back to power outputs lower than CP, w’ will be recharged.
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This may seem like a stupid question… But what have you got set as your FTP for that ride (shown near the top of each activity page, can be changed through the /settings page)? The W’(bal) calculations will be based off of that, so if you have not updated your FTP in settings for a long time and it is significantly lower than your eFTP / that shown on your power profile, that would explain what you are seeing here.
My FTP was set to 321w, and was upgraded to 333 in this race.
Maybe I just don’t understand the concept of W’ prime.
Is this not a value untill complete depletion?
Because if you can push through your anaerobic total balance, then the value is off.
I thought this was a value I could use for a race. When I hit 0% I’m all out. But if I can work the numbers into negative, then when is my body all out.
Does it make any sense what I’m saying??
If you hit -ve then it’s time to reassess your W’Prime number and extend it to the new number.
I may have missed it but I don’t think intervals will automatically update your FTP (or W’) in /settings as used for this calculation, or at least mine doesn’t get automatically updated!
Another consideration though if your FTP is set “correctly” is that it might still be too low and you need to do a consistently paced FTP test to determine what your actual FTP is right now - considering this ride gave you a “new” FTP even though it was very surgy.
FTP is also not a static number, and can change daily. In a race, the ability to go that little bit extra is usually higher than in training.
Is 75 kJ a plausible number though? Seems to me rather high, is there any lab statistics on this parameter?
If I iterate through the models on the power page, I can get wildly different fit values for both W’ and CP. On the other hand, computing W’ from the activities is very simple and should be reliable — unless the FTP is very wrong as mentioned above.
By the way, is this your usual power meter?
I always remember the case when a top professional triathlete Lionel Sanders bragged about his very high power intervals on a trainer until he discovered that his bike power meter reads 30+ watts lower
I guess it is possible if you don’t manually update FTP.
I updated my FTP and yesterday’s race showed a more accurate picture (I guess).
I turned the W’bal down to 20400 as shown on my power page.
Set my FTP to 333w.
I scored a new FTP yesterday on 335w.
It said my total W’bal was 26kj
I guess I’m closing in…
Thanks for all your replies. Keep them coming, if there is more to be learned here. 
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Hehe. I use this:
Garmin vector on Garmin Edge.
Wahoo Kickr on Zwift.
I usually compare the 2 on Zwift power and they aline with +/-1%'ish.
Vector get calibrated every time before use.
Kickr ones a week.
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