Effect of Sildenafil Citrate on Exercise Capacity in Athletes With Spinal Cord Injury

Ingestion of sildenafil citrate has performance-enhancing effects at high altitudes above 3800 m in able-bodied individuals. It is unknown whether it can improve the performance of athletes with spinal cord injury (SCI) at moderate altitudes (<2200 m), relevant to Paralympic competitions. As most men with SCI suffer from erectile dysfunction of neurologic origin and use sildenafil on a regular basis, it seems important to study the impact of sildenafil on exercise capacity. The outcome of this study is also relevant to the antidoping community.

Twenty-seven healthy male wheelchair athletes with a motor-complete SCI participated in this prospective double-blind, randomized, placebo-controlled study. The participants performed arm cranking exercise to exhaustion at sea level and moderate altitude (2200 m) after ingestion of 50 mg sildenafil citrate or a placebo. Peak power output, peak oxygen uptake, peak heart rate, rating of perceived exertion, oxygen saturation, and lactate concentrations at exhaustion were measured.

Friedman analysis showed that peak power output at sea level was significantly higher (P = .004) under placebo treatment (median [minimum; maximum]: 120 W [35; 170]) compared with sildenafil (115 W [40; 165]). Blood oxygen saturation under sildenafil treatment at sea level (98% [81; 100]) was significantly higher (P = .006) compared with sildenafil treatment at moderate altitude (94% [85; 100]). All other parameters revealed no impact of sildenafil or altitude.

In this study, the ingestion of sildenafil citrate in athletes with SCI demonstrated no positive effects on peak arm-cranking-exercise capacity compared with placebo either at sea level or at moderate altitude.