U.S. scientists, looking for a way to help soldiers perform in Afghanistan's mountains, have found a miracle pill that safely helps the heart and lungs work at high altitudes - Viagra.
In tests on cyclists in the thin air of high altitudes, it helped may men ride taller in the saddle, though it didn't boost the performance of everyone.
Viagra was invented as a drug for high blood pressure, and works by making some blood vessels relax and carry more blood. It was only while testing it for safety in volunteers that doctors recognized its happy sexual side-effects - which went on to become the main reason for prescribing the little blue pills.
Pfizer and its investors have never looked back.
But the heart benefits are still there. And scientists from Stanford University Medical Center and the U.S. Department of Veterans' Affairs set out to test a theory that by helping the heart and lungs circulate oxygen-rich blood, it might help athletes or workers at altitudes where the air is thin.
They set cyclists pedalling, comparing their performance with the drug and with a placebo.
At sea level, Viagra didn't help. But, as the researchers made the air thinner in a test chamber that simulates mountain conditions, they found some men using Viagra could circulate oxygen to their muscles so well that it raised their ability to work by as much as 45 per cent. Overall, this group improved by 39 per cent, as measured in time trials on a stationary bicycle.
Other men, for unknown reasons, found no benefit at all. And women haven't been tested yet.
And would there be side-effects with Viagra?
``Oh yeah!'' affirmed Roger Pierson, a fertility researcher at the University of Saskatchewan.
The drug expands many blood vessels, he said. And if it's helping the lungs, it's creating an erection too. 
``It's also going to leave you with a headache,'' he said.
The 3,874-metre altitude in the test is similar to peaks in central Afghanistan, or the Swiss Alps.
Viagra helped four of the 10 men in the study, reports Anne Friedlander, a hormone researcher with Stanford and Veterans' Affairs. (All the men were strong cyclists). Oddly, the ones it helped most were the ones who had the most trouble with the thin air in the first place, suggesting that the drug could be of great help to people who suffer altitude sickness.
Some of the cycling men took the usual one-pill dose, while some took a double dose. The study was ``double blind,'' meaning the men weren't told who had the real pills. But it's a safe bet that some figured it out on their own.
Results are now published in the Journal of Applied Physiology.
But Dr. Alvaro Morales, a urologist at Queen's University, cautions that Viagra doesn't stay long in the body.
The report ``doesn't sound out of whack to me,'' he said. But ``for a soldier who has to work not just for an hour or two hours, like having an erection, but may have to work for six or eight hours, the effect of the medication may be very short-acting.''
It's the second recent news about Viagra. Last week, doctors in Los Angeles reported the drug has ``hardly any'' bad side-effects, but does have good ones.
Cedars-Sinai Medical Center found it helps to fight primary pulmonary hypertension, and improves blood flow and oxygenation to the heart muscle.
Doctors caution, though, that they have only short-term data, and still want to do multi-year studies.
Meanwhile, officials at National Defence headquarters in Ottawa turned down a chance to comment on the cycling study
