Originally Posted by
PeteHski
Given the definition of IF = NP/FTP, wouldn't it imply that your FTP was artificially low? I tend to record an higher IF on rides that involve repeated hard efforts with periods of recovery (e.g. Zwift races) where my NP is often higher than my steady state FTP. But 4 hours at at an NP equal to my FTP is never going to happen. I very much doubt pros can do that either, although they would get a lot closer - maybe 0.9 ish.
Just looking at some pro data, Paris-Roubaix was won last year with an NP = 341W over nearly 6 hours. I would expect Van Baarle's FTP is well north of 400W, so that would be at an IF = 0.85 at best. With a shorter 4 hour effort, maybe he could hit 0.9?
Dr. Chung explained it.
I don't have the paper at hand but a well known exercise physiologist showed that W' could be recycled faster than expended and that this asymmetry could result in higher IF than might be predicted by FTP alone, ostensibly (my guess) due the the nature of the VO2 slow component in the moderate, heavy, and severe domain. I was thinking Pros might be able to go briefly into the severe domain before the slow component rises much and then recover quickly in the moderate domain. Let's say a 2 minute or 120 second hard effort at 100 watts into the severe domain (beyond FTP range)or 12Kj. The idea is this 12kJ could be restored quicker than 120 seconds. Rinse/repeat. Since Pros probably have closer to 30kj, this effect would be greater than what I wrote. ( IF is based on Normalized Power). My interest in the topic started when I tried to explain obvious differences on a very reclined recumbent compared to an upright. I wish I could remember the guy, he posted sometimes in wattage and on slowtwitch. Anyway, I am wrong
Pros are known to be able to go really hard above threshold and recover, I thought this might explain the chart.