Personally, I just guesstimate it based on recent "full gas" efforts - eg, I'll take 80-ish% from a full gas 6 minute climb, or 95% from a 24 minute climb, or whatever in between (where the anaerobic contribution in terms is the same in terms of kJ). That, rounded, gives me about 265W as a recent estimate. So, then I go out to train and do, say, 4 x 8 minute climb intervals at around 108%, which is in the 285-290W range, and that's just about the most what's doable for me. Trying to kick them up a notch to 300W didn't quite work out and I started to fade. So, that's how I know the figure is roughly appropriate, at least from a training perspective. Hopefully in a month or so I'll be able to do them at 295W-300W and then I'll know I made some progress.
Would I be able to hold this power for a hour? That's a different question - probably yes, but I'm not sure if it's really relevant to whether it's appropriate for setting training zones and figuring out what power to hold for what interval duration. If 2021 sees racing return to something resembling normal I'll certainly try.
So, anyway, take the ramp test figure and just do the training based off it; if you can't do the higher intensity stuff properly, the number is too high. If you can do it with some power to spare, then try it and if it works out, mentally readjust the number a bit upwards. If you're not going to train, the number isn't even all that important anyway. If it comes to pacing a TT type effort, the worst thing which can happen if you use the number you've got is that you can fade a bit towards the end, and then you'll know that it was a bit optimistic.
In time you get a feel for what you can do.
Last edited by Branko D; 03-03-21 at 06:56 AM.