zFTP unfairly high

I recently did a race up the Grade and when I hit the top I saw an FTP
that worried me about moving up into A category from B. Then I realized for ZRL the threshold between B and A is 4.2w/kg so I thought I’d be in the clear. Then I checked my Zwift feed and it makes no sense. Somehow my zFTP is higher than my 20minute peak power and nearly as high as my 15 minute peak… which for reference is on a ~11minute climb, in an all out race, so fairly accurate. Anyone else have this happen with the Grade? Any way this can be adjusted?


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It’s because you’ve got a flat power curve from 5 to 20 minutes.
zFTP uses a degradation curve built from various points along your power curve. Look up Critical Power if you want more details.
Long story short, smash out a 5 minute maximum effort and your zFTP will get lower.

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Thanks Tom, so it’s basically the lack of data on best effort between 3-6minute. Tonight’s ZRL in A should help that!

You can win or lose A races with these numbers. Ability to draft and knowing when to follow attacks is going to dictate which.