EurekAlert:

Sildenafil (Viagra) significantly improved the cardiovascular and exercise performance measures of trained cyclists at high altitude, mostly because the drug helped some participants improve a lot — up to 45% — while others showed little change. Sildenafil provided no benefit at sea level.

Ten cyclists who took sildenafil at altitude collectively lowered the time it took to cover six kilometers by 15% compared to placebo trials at altitude. The cyclists also significantly improved stroke volume (the volume of blood moved out of one ventricle of the heart per beat) and cardiac output (stroke volume times heart rate) compared to the placebo trial. Sildenafil also minimized the decline of arterial oxygen saturation of the arteries when the cyclists were at simulated altitude of 12,700 feet.

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