Mindweak, you answered my question with a general vision of training.
My question was different, and I go to formulate the same question in different way.
I have an athlete who doesn't use any drug, looking at training only (I think that, in spite of what you suppose, somebody clean in the world there is...).
This athlete run 10000m in 31' and a Marathon in 2:20.
He trains with a volume of 60 miles per week, including one track session based on 400m and 600m for a total volume of 6 km a little faster than the pace of the race (for example, 10 x 600m in 1'50" with 1'30" recovery) and one session on the road long at maximum 15 miles a little bit slower than his Marathon Pace.
After two months, his long run becomes faster (at his Marathon pace) or longer at the same speed used before (till 18 miles). His track session becomes longer, using in alternated weeks or a higher number of repetitions (for example, 15 x 600m with the same time and the same recovery used before) or longer tests (for example, 7 x 1000m in 3'05"). His total weekly volume raises till 80 miles per week, and at the end he runs 30'20" and the Marathon in 2:18.
After some month, he uses a total volume of 100 miles per week, including a session of 18 miles at Marathon pace, and a session of 22 miles at 85% of Marathon Pace. On track, he goes for a total volume of 12 km, alternating long tests (for example, 3 x 2000m in 6' + 6 x 1000m in 2'55" with 2' recovery) and short tests faster for a total volume of 6 km (15 x 400m in 65" recovering 1').
At the end of this period, he is able running in 29'40" and the Marathon in 2:15.
Finally, the next year he goes for a total volume of 120 miles per week. His long run easy is at 80% of his Marathon Pace, but becomes longer (till 30 miles), the long-specific run for Marathon (used only 3 or 4 times) developed at Marathon Pace becomes 18 miles - 20 miles - 22 miles - 24 miles, his longest track sessions arrive at 15 km including longer tests (for example, 2 x 3000m in 9' + 4 x 2000m in 5'55" + 5 x 1000m in 2'52"), and when are of 6-8 km are very much faster (15 x 500m in 1'20" - 1'22" with 1'30" recovery).
At the end of this period, the athlete is able running 29' and 2:12 in Marathon.
My question is : WHY INCREASING TRAINING HE CAN INCREASE HIS PERFORMANCE ?
What you explained about training is correct but is very simple. The problem is that, increasing training, we continue to increase the physiological modifications in our body, and this is the reason because the athlete can run faster.
You wrote :
"The mean Hct of the six subjects before rhEpo treatment was 45.7 ± 0.5%, increasing to 48.3 ± 0.8% within 1 week with the 35000 IU dose of rhEpo. After the 8 week intervention period, the mean Hct for the whole group was increased significantly to 51 ± 1% (Figure (Figure1).1). Three of the six subjects received full treatment dosage with a total of 70.000 IU rhEpo over 8 weeks, while two subjects were administered 67.500 and 62.500 IU, respectively. The remaining subject exhibited a strong response to the rhEpo injections, and received a total of 50.000 IU. Epo treatment increased VO2 max by 8.3 ± 2% from 54 ± 3 to 58 ± 3 ml·kg−1·min−1 (Table (Table1).1)."
I don't know if you understand that these 6 subjects, without any rhEPO but increasing their basic training, could not only reach the same results (not about the level of Hct, but about the level of their VO2 max, which can reach with LOWER HCT than the level they had before training).
So, what this research (of course carried out for normal people, not trained) can show ? That with EPO people NOT trained can reach, without training, the SAME level they can reach with some basic training, without any doping.
You clearly underrate the effects (and not the AFFECTS) of training, thinking anything depends on the strength of some drug.
But the history of methodology in any sport can show that training changes the physiology of every human, the real question is TILL WHERE WE CAN CHANGE.
I know, for personal experience, that with high talented athletes is possible to change TILL THE WR.
I don't have any proof that, giving EPO, they could run also faster. But, looking at how fast talented athletes training in clean way are able to reach the highest levels, frankly I doubt that, at that level of talent and training, EPO can add some fuel to the engine.