can't find the study yet but here' s a report on it
Microdosage of blood can have a significant effect - and it can be difficult to track. This is the conclusion of a new Danish study from the Department of Sport and Nutrition at the University of Copenhagen.
In the research project, they took a group of nine well-trained men with an average age of 29 years and doped them with 135 milliliters of red blood cells corresponding to 'half a bag of blood'.
The result was not to be mistaken. Their performance in a time drive by bicycle was improved by 4.7 percent.