About Ronald : he is one of the athletes having natural very high Hct, and this is of course an important characteristic, but not fundamental. I several times pointed out that, when I was the head coach in Italy for middle and long distances, we had athletes winning Olympic in Marathon like Gelindo Bordin with 12.9 Hb and 39.7 Hct, and athletes bettering the National Record of 1500m like Gennaro Di Napoli with Hct 52 and Hb 18.8, and when was at 17.5 had problems of anaemia.
So, we can have in the same event athletes at the top with complete different blood values. Since there is no doubt that, with higher Hct, you can have a higher ability to transport Oxygen, if with this superior characteristic you are not able to run faster than somebody with a very lower value, is because there is some other factor in the body that goes to limit the performance.
And no, athletes taking EPO don't have lower heart rate because have a stronger stroke volume. The stroke volume is directly connected with the dimension of the heart, and the heart becomes bigger because of the aerobic activity, not because the assumption of EPO without activity. So, EPO can help the activity, but is not able to increase the stroke volume.
Remember that the heart is a muscle, and, how any other muscle, can increase size with the activity. Other problem is to look not at the size of the heart, but also at the cardiac wall thickness : the elasticity of the cardiac walls have great importance for determining the stroke volume, and this has nothing to do with EPO.
This means that there is no reason because athletes taking EPO have a lower heart rate than athletes NOT taking EPO, other than the increased viscosity, that means increased peripheral resistance to the blood circulation, with reduction of the velocity of the circulation (that is a limiting factor).
What you explain as "product of EPO" is exactly what happens as "product of training".
So said, I go again to the PRATIC preparation of scientists and researchers, when we speak about training methodology.
When I give some workout to an athlete, I well know the final effect ON HIS PERFORMANCE : so, I can say that with the combination of training A + B + C, in a proper proportion, and in different volume and intensity looking at the different period of preparation, I know what I go to produce under technical point of view. However, I don't know WHY. It's clear this training produces physiological variations, in combined way, BUT NOBODY IS ABLE TO EXPLAIN WHY.
Why what is perfect for one athlete, can be dangerous for another, able to run the same distance in the same time ?
Why we speak about INDIVIDUALISATION of training as one of the most important factors ?
So, I know which performance I go to produce with my training, but I don't know the scientific reason.
On the other side, scientists and researchers DON'T know what a specific training can produce, but also don't know the scientific reason, simply because they NEVER went to study the training and the INDIVIDUALISATION of it.
This is called METHODOLOGY, and is something belonging to the PRACTIC ABILITY to coach.
And, again, scientists and researchers don't have any formal preparation in that direction. If they had, didn't do so many researches without any final clue, repeating thousand times the same tests and the same protocols.