If you're doing "intervals" over 1 hour (hills, burst of effort, etc), such that the VI is significantly higher than 1.0 (say above 1.15 maybe?), you're no longer working your FTP, so you cannot use that to correlate the NP to your FTP. However, if on your rides your NP is frequently over your FTP over 1 hour, and assuming you're trying to keep a reasonably steady effort, then this is an indicator that your FTP is under-estimated. Rob
Your "true" FTP is not worked out by multiplying anything by 0.95. Your true FTP is ascertained by finding out what you can do 'all-out' for ~1hr on a regular basis.
I'm actually surprised to read this.... I figured, for example, that if a person does high intensity interval repeats for one hour (say 2 mins on, 2 mins off), NP would not necessarily be a good indicator of FTP (I thought I'd read that somewhere). I don't question you at all (have and love your book) - but I'm really surprised.acoggan said:
As its difficult for me to do true 60min TT-type rides ar more or less even intensity to determine my FTP, knowing that I can use NP on irregular terrain is actually good news! Do you have any online articles I can read about this? Thanks! Rob
Indeed the higher the (ugh) VI is, the more likely NP (from a hard hour) is a better indicator of FTP than AP.
VI is an acronym for Variability Index, a term coined to represent the ratio of Normalised Power to Average Power.
Actually, it is even predictable. Let's say that your FTP is 250W and you do interval sets as you describe (2mins on + 2mins off) for an hour. If you do the "on" segments at, say, 275W, you should be able to do your "off" segments at 213W. You can always back into this calculation by using the NP formula in which you compute the weighted average of watts to the fourth (exponential) power. I sometimes do an FTP ride exactly like this on my trainer to break up the monotony of constant power rides.
No worries (to/for Rick, either), I just figured that if I didn't say anything, people would be even more likely to think we are one-and-the-same person. (Not that that would happen in real life, since I'm much better looking. /img/vbsmilies/smilies/ROTF.gif)
