MONDAY, May 3, 2010 (HealthDay News) -- Human growth hormone, a substance frequently implicated in sports doping scandals, does seem to boost athletic performance, a new study shows.
Australian researchers gave 96 non-professional athletes aged 18 to 40 injections of either HGH or a saline placebo. Participants included 63 men and 33 women. About half of the male participants also received a second injection of testosterone or placebo.
After eight weeks, men and women given HGH injections sprinted faster on a bicycle and had reduced fat mass and more lean body mass. Adding in testosterone boosted those effects -- in men also given testosterone, the impact on sprinting ability was nearly doubled.
HGH, however, had no effect on jumping ability, aerobic capacity or strength, measured by the ability to dead-lift a weight, nor did HGH increase muscle mass.
"This paper adds to the scientific evidence that HGH can be performance enhancing, and from our perspective at WADA [World Anti-Doping Agency], lends support to bans on HGH," said Olivier Rabin, WADA's science director.
The study, which was funded in part by WADA, is in the May 4 issue of the Annals of Internal Medicine.
Human growth hormone is among the substances banned by the WADA for use by competitive athletes. HGH is also banned by Major League Baseball, though the league doesn't currently test for it.
HGH has made headlines in the sports world. Recently, American tennis player Wayne Odesnik accepted a voluntary suspension for importing the substance into Australia, while Tiger Woods denied using it after the assistant to a prominent sports medicine expert who had treated Woods was arrested at the U.S.-Canada border with HGH.
However, based on anecdotal reports and athlete testimonies, HGH is widely abused in professional sports, said Mark Frankel, director of the scientific freedom, responsibility and law program for the American Association for the Advancement of Science.
Prior research has suggested HGH reduces fat mass, Rabin said, as well as help the body recover more quickly from injury or "microtraumas" -- small injuries to the muscles, bones or joints that occur as a result of intense training. That type of a boost could put athletes at a competitive advantage, Rabin said.
But research as to whether HGH is actually performance-enhancing -- that is, making athletes stronger or faster -- has been limited, according to the research ream, led by Dr. Ken Ho, of the department of endocrinology at St. Vincent's Hospital, Sydney.
In the study, Ho's team found that the improvement in sprinting speed for athletes on HGH was the equivalent of a 4 percent gain. In runner's terms, that means an athlete who typically runs the 100-meter dash in 10 seconds could shave off a bit less than half a second of time. Or, in swimmer's terms, it's the equivalent of shaving off 1.2 seconds from a 50-meter swim normally done in about 30 seconds.
"For athletes, it is sufficient to make a very significant difference in terms of winning or losing a competition," Rabin said. "It's the difference between being the winner and the last one in the finals."
Sprint capacity returned to normal six weeks after participants stopped receiving injections, according to the study.
Yet the study has limitations, Frankel said. Researchers could not say with certainty whether the athletes improved sprint ability because of HGH or because they trained harder during the 8 weeks of the study. And many athletes take HGH believing it will boost endurance, strength, power and other physical abilities -- effects the study did not find.
"Athletes may be taking HGH as a means of trying to improve their performance, even though there is some concern about whether it really does that," Frankel said. "If it does, and that is a big 'if,' it is certainly in the class of enhancement drugs that change the playing field."
Among the reasons WADA bans HGH are health concerns. In the study, athletes who received HGH were more likely to complain of swelling and joint paint more than those who received the placebo. Side effects could be more severe at the higher doses probably taken illicitly, researchers said.
Currently, blood tests are used to detect excess HGH circulating in the body that can indicate an athlete is taking it, Rabin said.
The World Anti-Doping Agency has more on the issue.