Ramp test vs FTP test inaccuracies

General Discussion
21

Zwift can also update your FTP outside of ramp/FTP tests if you happen to do a strong 20min session at some point within Zwift. Is it possible you did 20mins at about 238W? If so Zwift would update your FTP to 226W for instance.

22

That’s entirely possible, thanks for pointing that out. It’s hard to see (for me at least) how Zwift determines your FTP and which FTP value it uses for workout plans (zFTP? latest ramp-test? random previous short session?). Would be great if the app could be more transparent and/or give choice to the user.

23

Perhaps your FTP is set too high or overestimated by the test, but it’s also possible that the test result is good but the demands of the training plan you’re on are too great and it’s either designed badly or you need more recovery between the hard efforts. This is one of the weaknesses of a static plan that does not respond to your state of recovery. There are smarter training systems out there. A lot of the Zwift plans are quite optimistic about how much intensity you can handle, and even when they’re not, it’s expected that you may need to adjust the frequency or intensity of the workouts based on how your body responds.

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24

It is slightly confusing.

So there are basically 3 FTP related things in Zwift.

  1. FTP tests: If you take an FTP test (ramp test, 20 min test etc) and you improve your FTP based on this test Zwift will change the default FTP the game uses for workouts. This might or might not affect your zFTP depending on the effort and your current zFTP.
  2. Automatic FTP detection: Zwift keeps track of your best 20min power, and if you do a strong 20min average power Zwift can update the FTP used for workouts based on that. What Zwift does in this case is take the best 20min power you have and multiply it by 0.95. If that is higher than your current FTP Zwift should show a banner in the game saying ‘FTP increased’ and that will update the FTP used for workouts.
  3. zFTP: This has nothing to do with the FTP used for your workouts, which can be confusing. zFTP (along with zMAP) is used primarily for determining your racing category. This uses multiple points on your power curve (for instance one shorter effort - such as 5-6mins, and one longer effort such as 12-15mins) to calculate a value used for category enforcement. This will be entirely separate to the FTP you proactively set, get from an FTP test, or from 95% of your best 20mins in Zwift.

Note: You can always change the FTP used for workouts in your settings, but you cannot just change your zFTP or zMAP which is what is used for setting your race category.

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