Kressler, J., Stoutenberg, M., Roos, B., Friedlander, A. L., Viskochill, R., & Jacobs, K. A. (2009). Sildenafil does not improve exercise performance during acute hypoxia in trained men or women. ACSM 56th Annual Meeting, Seattle, Washington. Presentation number 1097.

"Sildenafil has been shown to improve maximal exercise capacity in men during hypobaric and normobaric hypoxia (~4,300-5,800 m) by enhancing pulmonary vasodilation, thereby improving cardiovascular and pulmonary function and enhancing oxygen delivery. Sildenafil has also been shown to improve submaximal exercise performance during acute normobaric hypoxia (~3,900 m) in some, but not all endurance trained men. Currently, the effect of sildenafil on exercise performance in women at any altitude is unknown."

This study determined whether sildenafil enhanced exercise performance in endurance trained men (N = 20) and women (N = 15) during acute normobaric hypoxia. Following determination of peak exercise capacity (Wpeak) at sea level and acute normobaric hypoxia (12.8% FIO2 , ~3,900 m), trained cyclists and triathletes completed two consecutive cycling exercise tests (30 minutes at 55% Wpeak + 6-km time trial) at normobaric hypoxia one hour following the ingestion of either placebo or 50 mg of sildenafil citrate. Cardiovascular hemodynamics (heart rate, stroke volume, cardiac output) were measured continuously by noninvasive impedance cardiography while arterial oxygen saturation (SaO2 ) was measured by pulse oximetry.

There were no differences in cardiovascular hemodynamics during steady state exercise between the placebo and sildenafil treatments for either men or women. Sildenafil resulted in significantly higher SaO2 values compared to placebo during steady state exercise only in women. Sildenafil did not affect 6-km time trial performance time, average power output, or SaO2 in either men or women. The average intensity during the 6-km time trial was ~70% Wpeak for men and women.

Implication. Sildenafil does not enhance exercise performance for a majority of endurance trained men or women during acute normobaric hypoxia due to its inability to alleviate hypoxia-induced decrements in oxygen delivery during high intensity exercise.

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