Reports of doping by Russia’s Olympic athletes continue to grab headlines. Just yesterday, officials confirmed that 14 of the country’s athletes from the 2008 Games had been implicated by the I.O.C. in a re-testing of samples. But doping in sports is not new. As early as the 8th century B.C., Greek athletes found ways to boost testosterone to enhance performance, says Northeastern’s Rui Li, an expert on exercise physiology. Here, she talks about the science of doping and possible measures to stop it.