The skeptics are wrong and the cheaters are right — human growth hormone does enhance athletic performance, new research suggests.
The Australian researchers who conducted the study said the work shows HGH, as it is called, might shave 0.4 seconds off a 10-second time in a 100-metre sprint or 1.2 seconds off a 30-second time in a 50-metre swimming event.
But beyond the basic fact that the study shows HGH works, experts warned against drawing too many conclusions about the magnitude of the edge it gives cheaters and the range of sports in which it might enhance performance.
That's because the study was done in recreational athletes who weren't following the rigorous training regimes of elite athletes, and who weren't taking the high doses the elite cheats use.
"Obviously they used dosages that might be a little bit tame compared to some of the insanity that may go on in the meathead locker room," said Dr. Doug Richards, director of the University of Toronto sports medicine clinic and a former team physician for the Toronto Raptors basketball team.
"It is difficult to do this kind of study, given the shady nature of some of the use of these things. The people who are abusing them in the sense that they're cheating in sport aren't exactly A, doing controlled science or B, publishing their results."
The researchers said they chose to test the substance in recreational athletes because it would not be ethical to conduct this kind of study in elite athletes. The World Anti-Doping Agency's rules bar them from using human growth hormone.
But that doesn't mean some aren't taking it. In fact, HGH has been something of a doping agent of choice for years, because the sole test currently available for it can only detect the substance in blood for a few days after someone injects it.
There has only been one athlete caught for using HGH, British rugby player Terry Newton. His positive test last November was seen as a major victory for the anti-doping effort.
Still, the fact that there has only been one detection in what is known to have been decades of use points to how big a challenge HGH has been for those trying to stop doping in sport.
"It's been the drug of choice partly just because it's been scot-free," said Richards, who is team doctor for Canada's national women's basketball team and the national beach volleyball teams.
"The word on the street is 'Use this one and you won't get caught.' Period. End of story."
The study was funded by the World Anti-Doping Agency, which goes by the acronym WADA. Its director general, David Howman, said the findings will support the agency's push for HGH testing in U.S. professional sports leagues, particularly major league baseball.
Skeptics have claimed HGH doesn't really help athletes, so there's little reason to test for it.
"Our take home (message) is we're pleased that the study has shown that those skeptical people who said that human growth hormone didn't increase performance have been shown to be wrong," Howman said.
"I think what we've done now is prove that that is pretty silly," he said of the reluctance to test. "You really should have your eyes wide open for this."
Howman said WADA hopes to have a better test for HGH up and running by the end of this year or early next. That test would stretch the detection window to weeks from the current days, he said.
The study was done by researchers at the Garvan Institute of Medical Research in Sydney.
They randomly assigned 96 recreational athletes to get either HGH injections or salt water shots, which served as a placebo. Men in the study group were further assigned to receive either saline, HGH, HGH and testosterone (an anabolic steroid) or testosterone alone for eight weeks.
The researchers ran a variety of before and after tests on the participants to see whether improvement in performance could be measured. Participants were tested in their ability to pull a weight, perform a standing jump and sprint while cycling.
They saw no statistically significant improvement in the standing jump or weight test results, but the sprint capacity improved significantly. In fact, in men taking HGH and testosterone, it nearly doubled.
Participants who got HGH also lost fat and gained lean body mass, effects long attributed to growth hormone. Those effects were amplified in the men who got HGH in combination with testosterone.
But there was a high incidence of side-effects, including joint and muscle pain. Dr. Don Catlin, a leading expert in anti-doping, was puzzled by that, especially given the low dose of HGH used in the study.
Catlin, who ran the anti-doping labs at the Los Angeles, Atlanta and Salt Lake City Olympics, said he felt the researchers could have and should have done the study in elite athletes.
"The proper study of athletes is top level athletes," he said from Los Angeles, where he runs Anti-Doping Research Inc.
"Those are the ones you want to see because those are the ones who are taking the damn stuff. You can't compare these kind of athletes to NFL football players."
As for the of lack of impact for the weight pulling and jumping tasks, Richards said the findings don't prove growth hormone wouldn't help there. The findings might have been different if the dose used reflected how growth hormone is used by athletes who are training many hours a day every day, he said.
"These people weren't training like weightlifters," said Richards.
"In other words, they haven't looked at the interaction effect of Olympic level exercise with appropriate doses."
He and others said sports cheats combine banned substances in regimes more intensive and varied than what was tested here.
Dr. Gary Wadler, chair of the committee that compiles WADA's prohibited list, welcomed the findings, but fretted about the consequences of having scientific proof HGH works, particularly in combination with testosterone.
He said the news could give athletes the idea of using lower doses of testosterone in combination with HGH in the hopes they might slip through the testing net.
"I think this is good science, but it underscores the problems that we all deal with in trying to control this," said Wadler, author of "Drugs and the Athlete" and an associate professor of medicine at New York University.
"I'm always afraid to say this because people will say 'Aha! I never thought of that one.' It worries me to a degree." he said. "They're playing Russian Roulette with their lives."