Sildenafil does not improve steady state cardiovascular hemodynamics, peak power, or 15-km time trial cycling performance at simulated moderate or high altitudes in men and women

Abstract

Sildenafil improves oxygen delivery and maximal exercise capacity at very high altitudes (≥ 4,350 m), but it is unknown whether sildenafil improves these variables and longer-duration exercise performance at moderate and high altitudes where competitions are more common. The purpose of this study was to determine the effects of sildenafil on cardiovascular hemodynamics, arterial oxygen saturation (SaO(2)), peak exercise capacity (W (peak)), and 15-km time trial performance in endurance-trained subjects at simulated moderate (MA; ~2,100 m, 16.2% F(I)O(2)) and high (HA; ~3,900 m, 12.8% F(I)O(2)) altitudes. Eleven men and ten women completed two HA W (peak) trials after ingesting placebo or 50 mg sildenafil. Subjects then completed four exercise trials (30 min at 55% of altitude-specific W (peak) + 15-km time trial) at MA and HA after ingesting placebo or 50 mg sildenafil. All trials were performed in randomized, counterbalanced, and double-blind fashion. Sildenafil had little influence on cardiovascular hemodynamics at MA or HA, but did result in higher SaO(2) values (+3%, p < 0.05) compared to placebo during steady state and time trial exercise at HA. W (peak) at HA was 19% lower than SL (p < 0.001) and was not significantly affected by sildenafil. Similarly, the significantly slower time trial performance at MA (28.1 ± 0.5 min, p = 0.016) and HA (30.3 ± 0.6 min, p < 0.001) compared to SL (27.5 ± 0.6 min) was unaffected by sildenafil. We conclude that sildenafil is unlikely to exert beneficial effects at altitudes <4,000 m for a majority of the population.