Injections of human growth hormone (HGH) can unfairly transform an Olympic also-ran into a gold medallist, an Australian study has confirmed.
Research funded by the World Anti-Doping Agency has determined the time advantage that unscrupulous athletes can reap from the "extensively abused" natural substance.
"We found a four per cent improvement in sprint capacity," said Professor Ken Ho from Sydney's Garvan Institute of Medical Research.
Produced in pituitary gland
"So, over a 10-second (100-metre) sprint that would equate to a .4 second advantage ... For sprinters that's a long gap."
Human growth hormone, or HGH, is produced by the pituitary gland and it is vital for healthy bone, muscle and organ growth.
It is used legitimately to treat growth disorders in children or as hormone replacement therapy for people with a deficiency.
Anti-doping officials also suspect the abuse of HGH by athletes has been going on "over many decades", Prof Ho said, while an ability to detect this has only emerged over the past six years.
'Extensively abused'
Athletes were "supplementing the body with huge amounts of a natural hormone" to gain a performance benefit in training that would carry over to the track, field or swimming pool, he said.
"It is widely believed that it is quite extensively abused ... and if you take a hormone which is identical to what the body makes it becomes very difficult to detect it."
Prof Ho's study into the effect of HGH on physical performance involved 103 fit people, aged 18-40 and Sydney-based, who had daily injections of either HGH or a placebo.
Those given the HGH had a dose "on the low end" compared to levels typically used in sports doping, and over eight weeks they reported the expected symptoms of fluid retention and joint pain.
Strength, endurance not affected
They did not improve in scientifically controlled tests of their strength or endurance as, Prof Ho said, the "only measure which changed was the measure of sprint capacity".
"This is the first time that anyone has demonstrated that growth hormone has a positive effect on performance, but not in the way that most people expected," he said.
"The advantage comes not with greater power or strength but the provision of energy required for muscle to perform at the start of a burst of activity."
A test capable of detecting HGH abuse by athletes was in limited use for the 2004 Athens Olympics and was more widespread for the 2008 Beijing Olympics.
UK anti-doping authorities reported the first confirmed case of HGH doping by an athlete in February this year.
Driven by 'glory'
Prof Ho said elite athletes were often driven by the "glory" of a world record or gold medal win, and it was hard to see how they could relish such a result if doping was involved.
"People who will cheat always try to stay one step ahead of the law, so they are not easily caught but eventually they will be caught," he said.
His study is published in the international journal Annals of Internal Medicine.
