Bengt Saltin was with me in some specific seminar about training in altitude and methodologi for Marathon runner. For example, in 1998 we were together in Baden Baden, and we had occasion to well know each other, and to speak about real training experinces.
So, I don't have any doubt what he says is true. But I don't share his conclusion.
Till 2008, regarding the track season, many of the best athletes could stay in Europe for about 3-4 weeks in order to compete in several meetings, since the calendar was very much more full than today, and the prizes were more consistant. In many studies I did in the period 1992-2001 in Italy, with Kenyan too (since we had a good budget from the University of Torino for researching about every type of parameter regarding blood variations, and the possibility to use as "examples" long and middle distance runners, Italian and/or Kenyans, was very interesting for the researchers), I saw classic parameters (as Hct and Hgb) increasing after one week of stay at sea-level, for decreasing again after 3-4 weeks.
I already said normally Kenyan athletes, staying in altitude, when are tested in altitude don't have very high level of Hct and Hgb. Instead, they have a big MCV, very much higher than in people living at sea level.
I spoke about this fact with many specialists (hematologists and clinic professors), and nobody was really able to give an answer to this strange fact : the values of athletes (may be of normal people, too) living in altitudes BECOME HIGHER IN THEIR FIRST PERIOD AT SEA LEVEL.
Now, athletes come directly from Kenya, and goes back immediately after the race. This happens because there are no more meetings very close one another, and the top runners don't want to stay too long time at sea level, fearing to lose thier shape (as many times can happen, because not always in Europe their stay can be well connected with the possibilities of a good training).
I think the difference in the values can depend on this factor. Otherwise, if before 2008 there values were lower, while the best results are from the years before ?
You understand that, who looks at doping only, cant have any evidence from the real results of the athletes.
The EPO doping is from 1990 and 2002, according to many people. How is that the WR of steeple, 5000, 10000, HM and Marathon (for not speaking about 800m) men, and of steeple, 5000, HM and Marathon women, are ALL after this period ?
For other people, the fact performances on track didn't improve after 2006 is a clear mark that, after a better antidoping system, athletes needed to be clean, so their performances slowed down. But during the same period there was the explosion of HM and full Marathon, "because clearly everybody can use doping". So, for antidoping is possible to detect the doping of 5000 and 10000 runners, but not of HM and Marathon runners ?
And NOBODY speaks about the development of the training methodology. This development happened for long distances ONLY, because probably, about 1500m, the best methodology is still what we used 30 years ago.
So, for the most part of people, the improvement in some performance depends on doping only. In every human field there is some improvement, BUT NOT IN ATHLETICS. We are still thinking for running a record the only important point is TO RUN. We still hear somebody saying athletes don't need any coach, "because nobody can know his body as the athlete himself". But the problem is not to know your body, but "what you have to do for using in the right way your body", and this is another issue. You know your body also when you are sick, why do you go to a doctor ?
I don't say nobody uses doping. I know many athletes, in any sport, try to increase in artificial way their qualities. My position is different. But I cant accept the idea that, without any evidence, the only fact an athlete can run fast is, for many people, "the evidence" the athlete is not clean.