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

Purpose: 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. Methods: 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. Results: 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. Conclusions: 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.

Moderate-intensity Arm-cranking Exercise may not Improve Arterial Function in Healthy Adult Men

Endurance exercises, such as cycling or running, are useful for improving arterial function. However, people suffering from partial paralysis or arthritis are unable to perform these kinds of lower-limb exercises. In the present study, we explored the acute effect of upper-arm exercise on arterial stiffness in healthy men. Fourteen healthy adult men performed two experimental trials. The order of experiments was randomized between a 30-min arm-cranking exercise at 50% V̇O2max (A-trial) and a 30-min leg-cycling exercise at 50% V̇O2max (C-trial). The brachial to ankle pulse wave velocity (baPWV), brachial systolic/diastolic blood pressure and heart rate were obtained with subjects in the supine position. The baseline hemodynamic values were not markedly different between the two trials. Compared with the baseline value, the baPWV was significantly reduced at 30 and 60 min after the C-trial. In the A-trial, however, there were no significant changes in the baPWV throughout the trial. These results indicate that acute 50% V̇O2max arm-cranking exercise induced relatively little change in the baPWV, which was the opposite of the finding observed with leg-cycling exercise. Therefore, in order to improve arterial function via aerobic upper-arm exercises, the exercise mode/intensity or other approaches should be considered.

VO2 Kinetics during Moderate Effort in Muscles of Different Masses and Training Level

Purpose. To examine the relative importance of central or peripheral factors in the on-transient VO2 response dynamics to exercise with “trained” and relatively “untrained” muscles. Methods. Seven professional road cyclists and seven elite kayak paddlers volunteered to participate in this study. Each completed two bouts of constant-load “square-wave” rest-to-exercise transition cycling and arm-cranking exercise at a power output 50–60% of the mode-specific VO2peak presented in a randomized order. Results. In the cyclists, the mean response time (MRT) as well as the phase II VO2 time constant () was significantly slower in the untrained compared with the trained muscles. The opposite was the case in the kayakers. With respect to the relatively untrained muscle groups, while both demonstrated faster VO2 kinetics than normal (moderately fit) subjects, the kayakers evidenced faster VO2 kinetics than the cyclists. This suggests that there is a greater stabilizing-counterforce involvement of the legs in the task of kayaking than of the arms for cycling. Conclusions. The results of the present study provide no support for the “transfer” of a training effect onto the VO2 on-transient response for moderate exercise, but rather support earlier reports demonstrating that peripheral effects may be important in dictating this kinetics.