Published in The Lancet Haematology journal, the research found that while the drug recombinant human erythropoietin - commonly known as EPO - improved high-intensity lab test scores, it barely affected endurance and road race performances, which were similar for cyclists given EPO and those given a placebo.
Doping, or the use of performance enhancing drugs, is a major problem in many competitive sports worldwide, and professional cycling has been plagued for decades by high-profile cases of cheating.
Yet scientific evidence about what banned substances do or don't do is scarce, partly because it is impossible for scientists to conduct trials with professional cyclists, who are subject to anti-doping regulations.
For this study, researchers recruited 48 well-trained amateur male cyclists aged between 18 and 50 and, in a blinded trial, gave half of them weekly injections of EPO, and the other half placebo injections over a period of eight weeks.
The doses used were consistent with known practices in professional cycling, the researchers said.
EPO promotes the production of red blood cells, and it is assumed it will lead to increased delivery of oxygen to the muscles and therefore improve performance.
The cyclists then underwent a series of tests to evaluate different types of performance parameters. The first was a high intensity ride in a laboratory involving a ramp test, where pedalling resistance was increased every five minutes until exhaustion. The second, similar to a time trial, was a 45-minute lab-based endurance test at the highest power output.
The third test, 12 days after the final injections, involved a 110-km (68-mile) ride followed by a 21.5-km road race up Mont Ventoux, which often features in the Tour de France.
"We found that while (EPO) increased performance in a laboratory setting on high intensity tests, the differences largely disappeared in endurance tests, and were undetectable in a real-world cycling race," said Jules Heuberger, who co-led the study at the Centre for Human Drug Research in the Netherlands.
He said the findings, which go against claims in some sports literature that EPO can have great effects, may reduce the incentive for athletes to consider blood doping.
(Editing by Andrew Roche)
