Bears wide receiver Brandon Marshall caused a great engorgement in the wit of the sports commentariat when he admitted that he's "heard (of) guys using like Viagra, seriously" to gain a competitive edge on the field.

It wouldn't be the first time. Cyclists, runners, and football players have been allegedly popping the little blue pill to improve their athletic ability for years--but does it help? The short answer is that no one knows for sure. Correlations between Viagra and better performance (on the field) have been found in some studies, but not in others.

Here's the theory of why it would work: Viagra chemically relaxes muscles and opens arteries to help blood flow more easily. (To help it flow easily all over the body, but, you know, there's the primary mission.) With the blood flowing more easily, oxygen moves to the muscles more easily, which can (theoretically) improve endurance during competition. That's something like the idea that altitude training will improve your oxygen flow and help you move longer distances without tiring, which it does.