PARIS — Seven-time Tour de France champion Lance Armstrong submitted a hair sample for a surprise doping test in France.

The French anti-doping agency Wednesday published hair test results suggesting widespread use among French athletes of DHEA, a banned substance that can be used to boost testosterone levels.

Armstrong was approached for a hair sample Tuesday in Beaulieu-sur-Mer, where he is training, AFLD chief Pierre Bordry said. This was the first time the AFLD has tested Armstrong since he came back to cycling.

"He needs to know that he is like everyone else," Bordry said. "To have done this test yesterday was a good way to make him realize that he is like everyone else."

Anti-doping authorities have not traditionally examined hair samples, instead focusing on urine and blood tests. Hair tests are allowed under French law but not under regulations of cycling's governing body UCI.

"Yet another 'surprise' anti-doping control. 24th one. This one from the French. Urine, blood, and hair!" Armstrong wrote on his Twitter feed Tuesday.

"So I'm clear — never complaining about these tests," he added. "Anything to prove I'm clean."

Doping accusations, especially from the AFLD, have dogged Armstrong since the beginning of his run to a record seven straight Tour de France victories. He has never tested positive. He plans to compete in this year's Tour after a three-year hiatus from cycling.

The AFLD, meanwhile, announced the results of hair sample tests conducted on 138 French soccer players, rugby players, track and field athletes and cyclists.

Twenty-two tests, or about 16 percent, showed signs of DHEA or testosterone use. Body builders have long used DHEA, but until now it was assumed to be limited among other athletes.

Bordry called the results "quite worrisome," but said French athletes with "abnormal results" would not be sanctioned because this is the first time the AFLD has conducted hair tests.

"We hope that those who are taking these products stop taking them, because it's very bad for their health," he said. "It's more important to tell them to stop taking them than to sanction the athletes."

The World Anti-Doping Agency prohibits DHEA, but urine and blood tests have proved ineffective in detecting its use.

"We have essentially no chance of finding this substance," AFLD scientific expert Michel Rieu said.

It can be detected in urine or blood only within 24 to 48 hours of its administration, he said. Hair tests are more effective.