After repeated testing of a sample of Tour de France winner Floyd Landis's urine revealed apparent doping with testosterone, one detail seemed to seal the case: The sample suggesting there were artificially high levels of the hormone in his body was collected immediately after his stunning come-from-behind performance on the 17th stage of the 20-part race.
A lot isn't known yet about what Landis took and when he took it. But a lot is understood about testosterone, the naturally occurring hormone that makes males men. And none of it suggests that it would have helped Landis much if he had binged on a synthetic form of the man-juice right before his comeback ride.
Testosterone's abilities to enhance performance when taken at high doses accrue gradually, so athletes who abuse it usually do so over an extended period, experts say. This stuff is not Popeye's spinach.
The conventional wisdom is that "you need a while for it to work," says Linn Goldberg, an internist at the Oregon Health and Science University in Portland and a spokesman for the Endocrine Society.
When taken over time, testosterone can confer a number of athletic advantages: increased muscle strength and size, improved bone strength and a higher count of red blood cells, which transport oxygen to demanding tissues. Source.