Athletes in the Vancouver 2010 Winter Games are likely to use blood-doping to boost their performances, experts have warned.
The banned practice involves getting a blood transfusion near game time to get more, richer blood than nature can produce.
Some athletes practice this because blood carries oxygen to the muscles, so more blood means more oxygen-and potentially better performances.
There are two known types of blood doping. One uses ordinary transfusions, and that's easy to catch today, says Harvey Klein, chief of transfusion medicine at the U.S. National Institutes of Health.
"You can look for the foreign cells. They have different proteins on their surfaces, and we have very sensitive methods of detecting those," National Geographic News quoted Klein as saying.
Don Catlin, an anti-doping researcher who spent 25 years as head of an anti-doping laboratory at the University of California, Los Angeles, said a more sophisticated method is for an athlete to withdraw some of his or her own blood during training and store it.
The body then builds up replacement blood and, shortly before an event, the extra blood is injected back into the body.
This method can sometimes be caught by tests that can tell if a person's haemoglobin-the protein in red blood cells that carries oxygen to tissue-is suspiciously high.
But athletes using this version of blood doping have been known to inject blood in the morning, race, then have the blood withdrawn later, thereby reducing their chances of being caught by random tests.
In the Vancouver 2010 games, blood doping would "probably help almost everybody, even figure skaters. But the target group is cross-country skiers. They have had episodes of blood doping [in the past]," Catlin said.
Blood doping isn't just illegal, it's dangerous. Transfusions done at home, for example, can incur the risks of contracting blood-borne diseases and getting sick from bacteria growing in poorly stored blood.
Klein said that doping can also make the blood dangerously thick. In fact, he said, some athletes have died from efforts to overly enrich their blood.