In particular, Armstrong's doping program, revealed in an October report by the United States Anti-Doping Agency (USADA), gives Mr. Catlin pause. While scientists are better than ever at identifying banned substances, athletes still can game the system.
"We thought we had this whole problem nailed," he says. "We spent a lot of time trying to find the drugs and get them in pure form. But that doesn't deal with how you get the drug into the athlete, or the athlete sending in someone else's urine."
Others agree that the cat-and-mouse game of doping has changed from decades ago, when athletes were using cutting-edge PEDs that scientists couldn't detect. "I think the doping athlete today is looking to use tried-and-true doping agents in a manner to avoid detection, rather than find something currently undetectable," Dr. Stray-Gundersen says.
The financial advantage is clearly with the athletes.
"The annual budget for WADA [the World Anti-Doping Agency] is $28 million, which is the price of one good baseball player," Catlin says. "How do you expect to really catch guys with that kind of money?"
In the wake of numerous doping scandals in track and field and cross-country skiing, among other sports, the Olympics adopted WADA's World Anti-Doping Code in 2003. Its recommendations include having an independent third party (not the league itself) conduct the drug tests, a routine of rigorous and random in-season testing, and harsh punishments for athletes who are caught.
Under the code, athletes can be banned for two years for the first infraction and banned for life for the second. They also have to pick one hour a day, seven days a week, to be available for unannounced testing.
Scientists say frequency and timing are key to effective testing, and testing at the 2012 summer Olympics was more aggressive than ever. Half of all competitors were tested, as well as every medal winner.