Earlier research, including a 2004 German study at Everest Base Camp, has found Viagra can counter the effect of low oxygen at extreme high altitudes. Scientists at the University of Miami are trying to determine if Viagra is helpful at lower altitudes, those where major sports events might be held, The New York Times reported Sunday.

At Marywood University in Scranton, Pa., athletes have been recruited for a study on whether Viagra can help overcome the effect of air pollution.

Viagra, or sildenafil citrate, suppresses an enzyme regulating blood flow, which relaxes blood vessels. The same mechanism that can help men overcome impotence could help athletes by improving cardiac performance.

The drug has not been banned from athletic competition, and regulators do not know how widely it is used. One Italian cyclist was ejected from the Tour of Italy after Viagra pills were found in his father's car, but he was not formally charged with doping.

Depending on the outcome of the new studies, the World Anti-Doping Agency, based in Montreal, may issue a ban.