'At low altitude, peak exercise performance of subjects was significantly above age- and gender-adjusted normal values, indicating superior fitness in these subjects,' noted Fischler.

All participants were randomized to take either tadalifil, dexamethasone or a placebo, beginning the day before a cable-car ascent from Alagna, Italy, at 1,100 metres (3,609 feet), to 3,200 metres (10,499 feet).

They then ascended on foot to Capanna Gnifetti at 3,650 metres (11,975 feet). After an overnight stay at Capanna Gnifetti, the climbers finally ascended to Capanna Regina Margherita at 4,559 metres (14,957 feet).

A second round of cardiopulmonary exercise tests were performed 4-5 hours after arrival, and echocardiographic examinations were performed the next day.

'Reduced oxygen content in the air is the major limiting factor at high altitude. Reduction in exercise capacity goes in parallel to the reduction in oxygen up to an altitude of approximately 4,000 metres, said Fischler.

The results are slated for publication in the Aug 15 issue of the American Journal of Respiratory and Critical Care Medicine.