So, first off, I know my FTP is somewhere around 287. I recently signed up for Xert, so my fitness signature for FTP was something like 214. I did a hard workout a couple days ago to see if I had improved beyond 287, and used the ‘What’s my FTP’ app to track my progress. I hit 292 on the app, but then when I uploaded the workout to Xert, it showed my new FTP as being…266. Why the discrepancy? Should I now manually adjust my fitness signature?
Check the FAQ on how to assess if your signature is correct. This should help. Without looking at your profile, I would imagine your PP and HIE are quite high. This might be normal for you or may be due to invalid data in your progression history.
Also, the Garmin app is using only one ride, whereas the system online benefits from far more data.
I have a similar issue - I did a 30 km Zwift race yesterday - my old FTP was at ~200 W, but I felt really strong so I managed to keep the average at 226 W for 52 minutes. At the end, I felt like I easily could have continued at at least 210-215 W for another 8 minutes. Zwift estimated my FTP at 219 W.
However Xert states my 1 hour FTP is 198 W, and FTP at 200.8 W. In this case, I think Zwift is closer to the truth. I estimate PP to be slightly lower than actual.
What can I do to make the Xert FTP more accurate?
You can normally tell by all the yellow dots on your chart that something didn’t quite go right. See blog help section on checking your fitness signature. In your case, if you open the activity and go to Advanced, at the bottom, increase you PP to say 800W and click extract, you’ll see the correction. Simply save that signature and you’ll be all set for your next activity. Cheers.