A recent study shows that athletes who take growth hormones do not necessarily obtain an improvement of their performance.

While growth hormone helps athletes add muscle, it doesn’t seem to boost strength or exercise capacity. This could mean that sport stars such as New York Yankees pitcher Roger Clemens may risk their reputation for nothing.

The Stanford University studied published today in the Annals of Internal Medicine reveals that the artificially added muscle actually tires athletes and causes them to get hurt easier.

The healthy people involved in the experiment were aged from 13 to 45. After taking growth hormone under medical supervision, they gained around 5 pounds in weight, but nothing in physical force. Moreover, they were more likely to suffer from joint pain and carpal tunnel syndrome.

Human growth hormone is naturally produced by the pituitary gland in the body, in order to regulate height and muscle and organ growth. A synthetic version, approved by the Food and Drug Administration is also available. It is recommended for children who suffer from growth disorders or AIDS patients who have lost weight, and it was banned for other uses. The hormone is very popular among athletes as it is undetectable in tests and it can also be obtained easily, from distributors who sell it illegally. It can usually be bought from the Internet and can be ordered through mail.

"The Internet is so huge, most kids and people know that unless you're buying huge amounts, they're not going to prosecute you,'' said Charles Yesalis, a Pennsylvania State University professor of health and human development, in a telephone interview for Bloomberg.