We have two studies, one on Scottish 11:08 runners, improving 5.7%, and the other on Kenyan 9:00 runners, improving 4.46%.
From these we can already see a reduction of effect for the more talented 9:00 runners.
Like you said, we need the same experiment on 7:40 runners to best characterize any diminishing return.
I thought athletes inject directly in the vein, and not subcutaneously. I’m surprised anyone is taking CERA, after the publicity surrounding Riccardo Ricco and Ramzi busts, where drug maker Roche worked with anti-doping labs to develop a test for it “turning over proprietary compounds, called reagents, that would help officials test for their drug”.
One thing we know about Ramzi is that he was able to increase his training with the move of nationality to Bahrain. “ex-runner” didn’t automatically rule it out, but gave EPO partial credit, as it was one of several known changes.
Looks like there is something new there. Your meta-study said there were many other mechanisms to consider.
In the Scottish study “the authors suggest that while the increased blood O2 transport capacity can entirely explain the improvement in VO2max, it does not explain the increase in time trial performance.”
“Otherwise rHuEpo should have different mechanism that affects positively the sub maximal performance. Unsurprisingly, Boning et al. proposed many other factors that could account for the ergogenic value of rHuEpo.”
The sub-max performance seems to be a linked to a Thomsen study, where cyclists increased time to exhaustion at 80% peak power by 54% from 22 minutes to 33 minutes.
We have to speculate how a 54% increase in TTE at 80% peak cycling power would translate to elite running, or how well a 33 minute experiment represents longer events, like the marathon, where there are other known limiting factors.
I could not find the justification for saying the sub-max performance effect was “larger than expected by the increase in blood carrying capacity”. But they did note:
“Nevertheless, it should be considered the exponential relationship between fraction of vO2max employed and the time to fatigue as possible reason explaining the huge improvement in TTE.”
Some more interesting comments in the conclusions:
“Notwithstanding further research would be warranted to clarify some unclear points.”
“First of all, further studies should evaluate the effects of rHuEpo in top-class athletes.”