Researchers have shown a positive effect of growth hormone on athletic performance in a new study.
It showed a .4 second improvement in a 10-second sprint, enough to turn a last-place Olympic athlete in a sprint event - running or swimming - into a Gold medal winner.
The study justifies growth hormone being a banned substance, even though evidence of its performance enhancing effect has been very poor until now.
Growth hormone, produced naturally in the body, is important for growth and metabolism. Injectable growth hormone is available for people who have growth hormone deficiency. Many athletes use the drug because they believe that it bulks up their muscles and improves their physical performance (growth hormone "doping"). Until this study, no scientific research had been undertaken to show that growth hormone improves physical performance.
Researchers at Sydney's Garvan Institute of Medical Research demonstrated that growth hormone increases an athlete's ability to sprint on a bicycle, but has no effects on fitness, weight lifting or jumping. The effect on sprint capacity nearly doubled in men who received testosterone injections in addition to growth hormone supplementation.
The study looked at 103 healthy recreational athletes, aged 18 to 40 years, who had engaged in regular athletic training for at least a year. It was double-blind and placebo-controlled, meaning that neither the investigators nor the participants knew who was receiving the drug or dummy injections (salt water).
Professor Ken Ho, head of pituitary research at Garvan, as well as Chairman of the Department of Endocrinology at St. Vincent's Hospital, undertook the project with Drs Udo Meinhardt and Anne Nelson, as members of a larger team.
Their findings are published in the prestigious international journal, Annals of Internal Medicine.
"Those athletes given growth hormone improved their sprint capacity by 4-5 percent," said Professor Ho.
"Growth hormone recipients did not increase their muscle mass. They did, however, retain body fluid and experienced swelling and joint pain, unlike those who received salt water injections."
"We used lower doses of growth hormone than athletes are reported to use, and for a shorter time. We can speculate, therefore, that the drug's effects on performance might be greater than shown in this study, and its side effects might be more serious."
"In conclusion, growth hormone increases athletic sprinting when given alone or in combination with testosterone. This is the first demonstration of improvement in a selective aspect of physical performance with growth hormone. We believe that this effect may bring a competitive advantage to athletes engaging in sprint events."