Human growth hormone significantly increases sprint capacity in healthy recreational athletes

During the eight-week study, 96 recreationally-trained athletes ages 18 to 40 (63 men and 33 women) were randomly assigned to receive either an inactive placebo or HGH injections. At the same time, half of the male participants were also randomly assigned to receive an additional injection of placebo or testosterone. Participants, investigators, and those who measured outcomes and analyzed data were blinded to interventions.

At eight weeks, the researchers found that HGH injections increased the athletes' ability to sprint on a bicycle but had no effects on fitness or their ability to pull a weight or jump. The effect on sprint capacity was nearly doubled in men who also received testosterone injections.

"We found the enhancement in sprint capacity would correlate to a 0.4 second improvement over 10 seconds in a 100-meter dash." said Dr. Ken Ho, Head of the Department of Endocrinology at St. Vincent's Hospital in Sydney, and lead author of the study. "This improvement could turn the last place finisher in the Olympic finals into a gold medal winner."

In addition to improvements in sprint capacity, researchers found that HGH significantly reduced fat mass among the athletes, but did not increase muscle mass. Sprint capacity returned to normal six weeks after participants stopped receiving injections. Athletes who received HGH complained of swelling and joint pain more than those who received placebo.

"In our study, we used doses of growth hormone on the low end of what is believed to be abuse in sports," said Dr. Ho. "And for that reason, we think that the real effects of growth hormone could be far greater than what's reported in our study. Equally, the side effects could be much more serious, as well."