It’s explained in the article:

The drug works by suppressing an enzyme that controls blood flow, allowing the vessels to relax and widen. The same mechanism facilitates blood flow into the penis of impotent men. In the case of athletes, increased cardiac output and more efficient transport of oxygenated fuel to the muscles can enhance endurance.

ESPN also have the story, less intelligently but pointing out some adverse effects (some of which have been hard not to notice):

How badly must you want to win to suffer the lingering effects of one Viagra too many? Have none of these athletes seen Chris Rock’s I Think I Love My Wife? The scene where even The Economist can’t tamp down expectations? He had to go to the hospital for that, and doctors did something there that cannot be repeated in polite company. This scares off no one?

Last months, Victor Conte explained the use of Viagra to USA Today:

Oxygen is transported into the heart to be pumped out to rest of the body. Viagra vasodilates (widens) the lungs and pulmonary arteries. This is where the exchange of carbon dioxide and oxygen occurs. So more red blood cells carrying oxygen get into the heart and more carbon dioxide is pumped out. It gives you stamina and endurance. Viagra could possibly accelerate the removal of fatigue acids and prolong the onset of fatigue. Would it help an offensive lineman who is making play after play after play? Yes. Would it be performance enhancing for a major league pitcher who’s throwing pitch after pitch after pitch? I believe the answer is yes. Would it help a sprinter? Maybe not in competition, but in training. They run one sprint, they walk one sprint. If you enhance your recovery in repeat sprints, ultimately you run faster in competition. The cardiovascular system is a two-way street. Blood is not only delivering oxygen it is removing waste. That keeps you from tiring more quickly, lacking endurance – and your pitches slowing down at the end of the game. IHT [intermittent hypoxic training] is growing at a rapid rate and it is of value to all types of athletes. It now seems that moderate exercise in a hypoxic training tent or while using a mask for just 30 minutes a day and three times per week can provide significant benefit to athletes. Viagra’s main benefit to athletes may turn out to be that it accelerates recovery.

Basic sciences only, academic / research center. Nor am I familiar with viagra in any other way [wink].

But remember, viagra’s main “effect” was originally a side-effect. The whole-body effects (hypertension) were one of the two original goals of the research. The blood pressure results were moderate, not terrible. They just realized that the side effect was a total gold mine, and moved that up to goal #1 for approval and sale.

I’m posting about this because it makes total physiological sense. Even if all the stuff does is to drop blood pressure under extreme exertion, while maintaining blood flow, it seems that should help the heart/lung process.

Heck, even if all it does is to make their skin flush, and dump excess heat faster, that could be an advantage. More blood deeper to tissues? Advantage.

We know the effect is dead obvious at extreme altitude. We also know that testers do not simulate “the best athletes in the world winning the sprint at the end of a long day’s racing.” That level of physiological stress would kill the average study participant, and the institutional review board would never pass that extreme a study design. It is inconceivable to me that it has no effect at the extremes of performance.

The downsides? (Besides chafing?) I’d expect it would exacerbate end-of-race blood-pressure drop / blackout. (Yes we’ve seen some of that this year. And yes, I am a Cancellara fan. And no, I’m not going to complain, so long as it’s legal.)