For athletes who didn't think possible to train with the new system because the intensity combined with the volume were too hard, so they cant recovery, doping was the reason that allowed them to train more.
But the fact is that it's possible to train at high intensity and extension without doping too.
The above athletes NEVER TRIED to train with the modern system BECAUSE SUPPOSED NOT TO BE ABLE TO RECOVERY, but the reality is they didn't try.
Athletes believing possible to train in this way without fearing volume and intensity are able to reach HIGHER PERFORMANCES in clean way.
So, it's not true that blood doping is the only way for being at the top of the world : it's training that brings athletes to that level. And this is the reason because normally doped athletes are not the number one, but number 50 - 30 that look at doping as the way for becoming stronger. These athletes are mentally more weak, and normally NEVER can become the strongest Champions.
It's absolutely possible to be the best in clean way in all the endurance event, while is almost impossible to be the best in short events, throws and many women events where the muscle strength is the most important physical quality, without doping with some family of steroids.
This doesn't mean the best women or thrower today are doped, but that the old WR are at the moment very far.
Some example for women : High Jump 2.09 (1987) today 2.02-2.05, Long Jump 7.52 (1988) today around 7.10, Shot put 22.63 (87) today less than 21m, Discus 76.80 (1988, I was there) today about 70m, Javelin 80.00 and after had to change the javelin (today 66m), 400m 47.60 in 1985) today more than one second slower, 800m 1'53"28 (1983), today around 1'55". And for men, Hammer 86.74 (1986) now max 82m, Discus 74.08 (1986) now max 71m, and Javelin (old implement) 104.80.....
So somebody has to explain why these record last from 35-40 years, while in long endurance we continue to improve.