The World Anti-Doping Agency (Wada) has said it hopes to soon have technology to combat the threat of "gene doping".
The move follows concern that gene therapy - used to treat chronic medical conditions - could be misused by unscrupulous athletes and trainers.
Professor Geoff Goldspink of University College, London, said he felt testing technology was "almost there".
"We can already detect illicit DNA and introduced gene products," he said at a doping conference in Athens, Greece.
Although there is no recorded evidence of athletes using gene therapy, professor Goldspink said it was important to be alert to the threat.
"We can put genes into mice and create 'Arnold Schwarzenegger' mice," he told delegates at the conference, organised by the International Olympic Committee.
"If it can be done on mice, it can be done on humans."
Professor Goldspink said laboratory mice had proved that gene transfer could lead to a 25% leap in muscle mass inside two weeks.
"It's inevitable that we will have this (kind of doping) if we don't already have it," he added.
"Once the technology exists for medical use disreputable people will be putting the stuff in athletes."
Congress delegates warned that gene doping presents a "clear and present danger" and that international sports authorities are facing the next generation of sports cheats.
Current testing methods to catch athletes using banned substances such as anabolic steroids are powerless to catch gene cheats, the conference was warned.