Sorry, but this is the biggest crock of shit. The guy who is finishing an IM in 16:50 may very well have the ability to suffer greater than you or even Patrick Lange. In fact, when I started triathlon (shortly after my rowing career ended), I would have put my ability to suffer up against anybody, including pros. But yet 15 years later Iâ€™m actually faster even though I will candidly admit my ability to suffer has diminished. Because I have trained a lot more more and the numbers are much better.
Sure, the ability to suffer is helpful and necessary, but itâ€™s not even close to the #1 requirement. I think the rest of your post is valid and underscores the point that power at 5 hours is more important than FTP. But, that is still a quaintifiable number.