Interesting question. I'm 23 year old, top of pack in most races I enter but nowhere near elite (raced Lisa Nordén in a short race, 800/14/3,3k and was 4 minutes behind her. During her plantar fascitis..) Last winter I had a minor knee surgery and couldnt bike for 2 weeks and run for 4. When I came back I couldnt run for 2 km straight. I did 400m repeats at 5:30/k pace. 4 weeks later I did my first 5k tests and managed 23 minutes. This was on running twice weekly (which I still do). I was swimming 400LCM in 6:20 something.

Now a good year later without any real setbacks (worst was the flu and some annoying shin problems) I swim a 400LCM in 5:40, my FTP is problably somewhere at 4w/kg and my open 5k is probably around 19. I dont even feel like I'm close to my potential. I've been into endurance sports, transitioning from martial arts and gym training, for 2-3 years now. My first tri was 2011 and with only bike training and I did a 1:22 sprint.

I cannot for my life understand why a healthy male would plateu - genetically - at 19k/3,75w/kg ftp/6:30 500y. Its just too mediocre. For females I can believe it. The general weekend warrior has so much potential to tap into if they would be allowed a few years (say 4, an olympic cycle) of elite training with training camps, weekly massages, qualified coaches, good equipment, motivating people around them etc. I'll say for a healthy male to NOT reach these numbers with 4 good years of training would be suprising and certainly an outlier on the low end of the bell curve.