I completed Week 9 Day 4 last night and failed to hit all the intervals (the 4th workout I couldn't complete all intervals since I started). The 90-minute workout had 6x5mins at FTP at the end, I got to the end of the 3rd interval and I knew that was all my legs had... I limped through the last 3 intervals. I'm not sure why I can't complete all the blocks. Is it the double-red blood cell donation I did last month (that left me really drained - ), or is the FTP set too high, or should the workout be difficult enough you can't always complete???

Here's the Strava graphic for last night's ride, I added marks to show where I feel short.



I'm really interested to see how I do when the summer bike hits the road... that will give me a better idea about the answer to my question.

I'm interested to know if anybody else had completed the 10-12 week FTP builder, what was your experience?