Abstract
<p>Sildenafil increases oxygen delivery and maximal exercise capacity at very high altitudes (greater than or equal to 4300 m) and has been shown to improve short-duration exercise performance in some individuals at simulated high altitude (3900 m). It is unknown whether sildenafil improves maximal exercise capacity and longer duration exercise performance at moderate and high altitudes where competitions are more common. Additionally, the effects of sildenafil on women exercising at altitude have not been examined. The purpose of this study was to determine the effects of sildenafil on cardiovascular hemodynamics, arterial oxygen saturation (SaO2), peak exercise capacity (Wpeak), and 15-km time trial performance, in endurance-trained men and women at simulated moderate (MA; 2100 m, 16.2 % FIO2) and high (HA; 3900 m, 12.8% FIO2) altitudes. Eleven male and 10 female subjects completed two HA Wpeak trials following the ingestion of placebo or 50 mg sildenafil in randomized, counterbalanced, and double blind fashion. Subjects then completed four exercise trials (30 min at 55% of Wpeak + 15-km time trial) at MA and HA following the ingestion of placebo or 50 mg sildenafil in randomized, counterbalanced, and double blind fashion. Sildenafil had little influence on cardiovascular hemodynamics for either gender at MA or HA, but did result in higher SaO2 values compared to placebo during steady state and time trial exercise in men at HA only. Sildenafil did not affect Wpeak or 15-km time trial performance in either gender at MA or HA. We conclude that sildenafil is unlikely to exert beneficial effects at altitudes < 4000 m for a majority of the population.</p>