I assumed that both tests accurately measure ftp. So what am I missing? For the last two months the result was the same, just with different tests. I had hoped to see a higher number based on how much I was riding and how many long rides I have been doing.
A lot to unpack in the 4 sentences you wrote.
Before I get any further I think you need to determine what you want to test. Is it your 2x8 min power or 20 min power both of which can be inflated if you have a high FRC /anaerobic capacity. Is it your FTP? The amount of watts you can hold for 20min, 45 min 75min? What are your performance goals? Knowing those will before you test and start a training block will guide your testing & training choices.
The 20 min test x .95 is accurate for about 60% of people. Are you in the 60% or 40%? 8 min tests - your anaerobic capacity will cover some of that which can artificially inflate your FTP # that you get. This depends on how much capacity you have. You will get some of that anaerobic capacity recharged in that 4 min rest between 8 minutes. In the first test you may have depleted it in 3 minutes and in the second test 1:21. Plus you allow some recovery between those testing bouts.
An 8 min test with rest then repeated does not = a 20 min test. As duration increases even at a steady state power, the physiological response will increase. How many people on ST do the 20 min test x .95 = FTP yet can’t hold that same effort for 40k or an hour?
A fuck load. Which is a lot.
Then they go try to do something like 3x15 min or 2x20 min intervals and fail. Why? Bc they’ve over estimated their FTP. 2x20, 3-5x15 ~ 96-102% FTP isn’t that hard of a workout. It’s hard, don’t get me wrong but it’s not as bad as say 4-5x6 min @112 -120% FTP.
I’d bet you $50 that you can’t go out and hold 275 (or what ever the # was, I forgot) for 60 min by Saturday. I’ve never lost that bet to anyone doing a 20 min x.95% test in all the years I’ve been on ST. 3 or 4 have taken me up on it.
If you did 2 shorter tests w/ some recovery between them and got the same # on a 20 min test I’d actually argue that your fitness is better with the 20 min test. Again holding an near/at/slightly above FTP effort becomes harder as the duration increases.
Just bc you’ve been riding a lot and doing a lot of long rides doesn’t mean you are going to see an increase. Sure riding a lot helps. If you’re normally riding 125 miles/wk and bump that to 150 you’ll get a small bump. Bump it to 200 and be consistent and you’ll get a larger bump in fitness. I had athletes during the early part of the pandemic increase the amount of watts they could sustain for 60 - 400 minutes by 15 -30 watts on a 3-4 week bike focus with < 4 interval workouts during that time. They increased riding by 75-125% and maintained that for 4 weeks.
Anyway hope that gives you something to think about before you test again or think your training isn’t working. it may be, you might not be assessing it accurately.