Hi all.
I did a ramp test yesterday, and, compared to the previous one 6 weeks ago, my FTP went from 247 to 262, so I was quite pleased with that (4W/kg, yay! 
). Today we had bad weather, so I decided to “test” my new FTP on the trainer by attempting to hold 262 watts for an hour, which, by the very definition of FTP, should theoretically be possible. However, I was only able to (just!) hold 262 for 30 minutes; I had to lower the power to 240 for the remaining half hour in order to be able to finish the workout. Average power over the hour was 251. Two questions: 1) Did the ramp test overestimate my FTP, and as such is it actually 250? 2) Should I manually lower my FTP value for the upcoming workouts, or attempt them as they come and see how it goes (I have a hunch that I will not be able to complete them; for example VO2 max intervals will go from 285W (hard but doable) to 305W…). Or if I fail, persist until I can complete them? Thanks.
Yes it has overestimated your FTP and no it is not necessarily 250W. As FTP is 40-70 min i would think it is in the middle around 255W maybe.
Yes. The VO2 should not necessarily need to be approached by power but rather by feel but longer, steady workouts can be painful. As you work in the zones 255 W is inly 3% reduction so you will get exactly the same benefits but you will be not working harder than you can.
There are lots of posts on this topic. You might search and find some other discussions to help you feel better. First, I’d say, take what the test says. If you can complete the workouts at that FTP, then that’s the most important thing. The actual number is kind of a vanity thing. Second, as far as being able to hold it for an hour, that may take work. It may be your FTP, but your fitness may not be well trained to hold any amount of power for an hour. There are some here who view that as a challenge and are practicing to work up to that. Bottom line is, stick with 262 as long as you can do the work the plan prescribes for you.
There’s a time-to-exhaustion component to doing the sustained 60minute test. If you’ve not been doing lots of longish sweetspot/threshold intervals you’re going to have a hard time holding on for a full hour. At the end of the day the plans and workouts are arranged to build off one of the ftp tests, and if you’re completing the workouts then I’d leave it alone. On the VO2 side of things coach chad is very clear: some people are vo2-inclined, and some aren’t, and there’s no shame in scaling them down a few %. Now, if you’re having trouble with the vo2 workouts AND the sweetspot/threshold, then you’ve got a problem and have overestimated your ftp (but if all you’re doing is z2 workouts that’s not going to tell you anything).
In my opinion FTP TTE of 30 minutes is the absolute minimum you should be able to hold your FTP, so for me you just make it. You should be okay to go forward with training at that level without adjusting it down (although it does depend on your experience and overall power profile, if gaining fitness quick you can sometimes outrun the progressions in some TR plans anyway.) Stick and see how you go.
I’d say its only a touch over, but not much (on a really good day could you have got to maybe 40 minutes.) Anyway nowhere near as bad as some people when they can’t even hold their ramp test FTP for 20 minutes.
As someone else said if the ramp was aligning well with your more realistic FTP you would be able to hold it for 40 - 70 minutes but don’t sweat it, should be okay for TR plan purposes.
Edit: if worried about it and start struggling with workouts look at the average for the first 40 minutes, I would say your FTP is NOT as low a 251w not that many people have an FTP (as I see it) around 60 minutes.