A new study suggests the skeptics are wrong and the cheaters are right about human growth hormone — it does enhance athletic performance.

The study, by researchers in Australia, suggests modest doses of growth hormone can improve sprinting capacity in sports that require bursts of speed.

The researchers suggest at the levels they were testing, athletes might shave nearly a half-second off their time in a 100-metre sprint or 1.2 seconds off a time in a 50-metre swimming race.

The study was done on recreational athletes because elite athletes could not take part in a study that required them to take banned substances.

"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 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 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 only test currently available for it can only detect the substance in blood for a few days after someone injects it.

1 athlete caught

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.

Experts say the results confirm the general belief among athletes that growth hormone helps, but they say elite athletes who cheat probably take the substance at higher doses than were tested in the study.

World Anti-Doping Agency 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."

Dr. Gary Wadler, chair of the committee that compiles WADA's prohibited-substance 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."