Racing performance improving (B->B+), zFTP in a tailspin

Over the last few weeks I have moved from a typical B rider, to a B+ rider. I can almost always finish in the first group in any race and make all the splits.

My racing average w/kg is usually around 3.9 for shorter races and 3.5 for longer races like the Zwift epic races.

Recently I have hit some personal bests on 1m and 5m power in races.

I have also ridden some A races, and, well…finished not last, hanging in the main group well into the second half.

However, my zFTP has declined from 315 to 291.

I’m wondering how this can be?

Because zftp is not ftp, it is an evaluation of a kind of critical power. When your 1 to 5 minutes power gats higher, it makes your zftp a little lower. If you continue to improve you will however get to A… I have been hanging on the upper side of B cat for years, with the last few months my zftp going up to 244 to 249w… and a little longer effort in a race took me to 250w and A cat, even with my very good power numbers in 1 to 5 minutes efforts.
If you go on getting better you’ll be A.


You can see my answer here for an explanation of what the critical power model is, and you should also be able to see why it is that if you did a fresh short duration effort, your zMAP estimate would increase but your zFTP estimate would decrease.