google: juniors, doping, Carmichael.

Some people deserve shunning.

As far as riding and/or training into geezerhood, I do not think intensity of short efforts is your enemy. It appears to me that -- with proper preparation -- HIIT may be the fountain of youth. There is, on the other hand, enough evidence of irreversible damage accruing (we think) due to extreme endurance effort that we ought to pay attention. Multiple hours at threshold is what I am speaking of. Not the sort of thing your average fit or even fast-after-50 athlete is doing.

I'm nowhere near Friel's preferred level of organization and planning, but I can vouch for the basic approach: a lot of Z2 base training followed by a build period incorporating a variety of HIIT, more Z2 "recreational" riding and (always) adequate recovery time. If you are fortunate to still be basically healthy, and have the work ethic and discipline to do this stuff... and the sense to back off and recover when any part of the bod says "enough", you will be amazed at what is possible. Set the clock back, fitness wise, a few decades.