This has probably been beaten to death already, sorry. But even after reading the definitions and a few discussions I still would like to be enlightened.
Before yesterday it’s been a year since I did an FTP test, the 20 min short test, and I ended up with 258W. Yesterday I did The Grade at a 282W average and saw 254W on the roadside sign. That’s fair, I’m a year older and am in the beginning of a cold.
Then I checked the data at intervals.icu, imported from Strava, and they claim my FTP went up to 263W. Still fair I guess, different platforms/sites may use different methods.
But where I get lost, is that my Zwift zFTP level went up to 264W – almost identical to my intervals.icu level. And, this is the value that really matters to Zwift, as this bumped me up to Cat B.
Don’t get me wrong, I fine with either of these values. And as a very, very old man I bear my Cat B stamp with pride and try to sneak it slyly into conversations. But I’m still confused what my FTP value «really» is. Also, where is it at all relevant, as it’s the zFTP that counts?
There’s so many ways people estimate FTP these days, ultimately choose a method and repeat it as your pin the tail on the donkey ballpark.
Apparently if using the 95% of your best 20mins method, most can hold that number for approx 40-55mins, with pros usually holding it towards that higher duration.
For racing, zFTP and zMAP are both relevant. FTP is not.
For workouts, FTP is relevant. zFTP and zMAP are not.
If your zMAP is relatively low that will tend to inflate zFTP, so ask yourself if your 90 day 5 minute PR (seen on my.zwift.com) is really the best you can do. If you do a better 5 minute PR, zFTP will most likely go down. But if zMAP goes up beyond the C category limit you may remain in B since you can get to B by exceeding either the zMAP or zFTP threshold.
Thanks for taking the time, appreciated. It’s getting clearer, I get that zFTP is fixed until you improve it or drop back, while FTP can be manipulated by user for harder or easier workouts.
My current zMAP and also my 5 min PR is 290W (3,8W/kg), I have no idea if that is high or low. But I have started wondering if my ageing legs and 77 kg heavy body are actually quite good at doing 15-20 min flat out climbs with total exhaustion at the top (in a relative sense, compared to for instance 60 min long races with several climbs): It is after doing one of the shorter climb portals or like now The Grade that I have been bumped up. It has never happened in other circumstances.
You can do an experiment where you warm up and ride for 5-6 minutes pacing at say 4W/kg and see if you can hold it. If you do that there is a fair chance zFTP will go down. Whether that will shift your category depends on the details.
I am about your weight, my best zFTP this year was around 250W, currently 231W because those numbers are only from racing, not FTP tests. My zMAP is 324W which puts me around 4.2W/kg - meaning my recent PR moved me to B based on zMAP alone. I don’t regret it since it was an all-time best 5 min and I got a tiny trophy to go with it. Plus that was from an uphill finish after an hour of racing so in theory I might do better if I had the proper motivation and preparation.
zftp is - with some differences in the nuances - based on CP/W’, or critical power if you want something easier to google. The numbers don’t align exactly, but the principle behind how it works and why it works that way is the same. Just in case you’re interested in learning about the concept, since a lot of people do find that to be a useful training metric
Just coming to this as someone whose zftp fell (significantly) after a 10min power pb.
Now that ZRS is in place will zftp be consigned to the dustbin? I trust intervals eftp much much more.
I’m a punchy rider with no endurance background but i can do 2x30 at my zftp and its not more than an 7.5/10 workout, because it is 25W too low! I don’t want to do a full ftp test, and frankly can tell by feel where i am with my progress on different types of effort.
I love zwift but this constant reinventing of things and doing it badly is becoming an organisational habit.
If course, I’ll happily sit some way from the pace group limits for ZRL…