Not sure if this has been asked before but here goes.
Say i've just been on a nice long ride, legs are feeling pretty cooked having done some hills and on the flat stretch on the way home I do 2 * 20 minute pieces, is this going to have any sort of relation to L4 work? Obviously my power output would be much lower than standard L4 intensity, probably be somewhere in the middle of L3, so will the adaptations this sort of work causes be similar to those of L3 (as power would suggest) or L4 as it the feeling of exertion is very similar to that of 2 * 20 at L4. I'm guessing at L3 but I would like to know what you think. (Levels are as in ACs training levels).
Not sure if this has been asked before but here goes.
Say i've just been on a nice long ride, legs are feeling pretty cooked having done some hills and on the flat stretch on the way home I do 2 * 20 minute pieces, is this going to have any sort of relation to L4 work? Obviously my power output would be much lower than standard L4 intensity, probably be somewhere in the middle of L3, so will the adaptations this sort of work causes be similar to those of L3 (as power would suggest) or L4 as it the feeling of exertion is very similar to that of 2 * 20 at L4. I'm guessing at L3 but I would like to know what you think. (Levels are as in ACs training levels).
You'd have to seriously, seriously cooked to not be able to manage to do your levels in l3. Remember the low side on l4 is 91% of ft, so I really don't see you being that far off.
But, I understand what you're saying, and I think that the adaptations to intervals done "underpowered" are pretty low. After all, I can ride in low l4 for 2+ hours, so what's the point of doing 40 minutes of it? But put into the context of the total ride, which might have included lots of long l3/l4 chunks, and the whole workout has serious benefits.