So i just got a power meter and did an ftp test, two actually. A 20 minute one and the 2x8 minute one. With the 2x8 one being 4 watts higher.
Now for my questing.
The standerd training zones percentages and the corresponding duration’s are WAY off. I can hold the high stuff for way longer then the charts say and my ftp feels about right while doing the 2x10mile tt test.
My ftp is 330W with me weighing 97kg at about 18-20% body fat. I do think that my PM is reading high but I went back to the store with it and told me it was on point. I started cycling in februari of this year.
Could you also do a Ramp test? It takes some practice to get these longer FTP tests right but during the Ramp test you will suffer really hard only for about 3 minutes. Just make sure you are rested before doing it.
Ramp test should give you about the same number as you got before. If it is much higher, that means you have under-performed in your previous tests (which is fine).
Depending on your individual power curve it could be skewed towards the shorter durations. For workouts with these types of intervals you might need to bump the intensity up a bit.