Before I started TR, I would do the dreaded 20 min outdoor test for FTP. Started TR 2 months ago and the ramp test showed an FTP 20 watts or so lower, BUT that seemed accurate for indoor workouts, and my higher outdoor FTP seemed accurate for outdoor workouts too.
So, I lived with 2 FTPs. Now, I think I have grown stronger. So, I’ll redo the ramp test, but outdoors, would the 8min test be OK? I HATE the 20 min test.
Also when I import an outdoor ride to TR, I edit the FTP in that to my outdoor FTP, so that the TSS would reflect accurately.
And, if I import an indoor ride to TodaysPlan, I edit the FTP there to match my indoor FTP [TP has ftp set as my outdoor FTP].
If you truly feel that your indoor and outdoor FTPs are misaligned, I’d recommend looking at how much difference there is between your indoor and outdoor, and then carry that offset to the next time you test. You don’t want to be doing two tests every time you need to reassess your FTP.
For example, if your outdoor FTP is 20 watts higher than your indoor FTP, just add 20 watts to your next Ramp Test results. This will get you as close as you need, and it saves you the added stress and complication of testing twice.
If you do want to test both independently, then the 8 minute test is a totally valid way to test. It may not line up perfectly with your 20 minute test results though depending on your strengths as a cyclist, so if you are looking for maximum consistency, it is best to stick with the 20 minute test. If you’re just looking for a good number to train based on, then the 8 minute test works great.