Purpose: Supplementation with inorganic nitrate has been suggested to be an ergogenic aid for athletes as nitric oxide donor. The purpose of this study was to determine whether ingestion of inorganic sodium nitrate benefits well-trained athletes performing a 40-min exercise test in laboratory conditions. In addition, we investigated the effect of this supplement on plasma levels of endothelin-1 (ET-1) and in nitrated proteins.
Methods: Thirteen trained athletes participated in this randomized, double-blind, crossover study. They performed a 40-min cycle ergometer distance-trial test after two 3-d periods of dietary supplementation with sodium nitrate (10 mg·kg−1 of body mass) or placebo.
Results: Concentration of plasma nitrate (256 ± 35 μM) and nitrite (334 ± 86 nM) increased significantly (P < 0.05) after nitrate supplementation compared with placebo (nitrate: 44 ± 11 μM; nitrite: 187 ± 43 nM). In terms of exercise performance, there were no differences in either the mean distance (nitrate: 26.4 ± 1.1 km; placebo: 26.3 ± 1.2 km; P = 0.61) or mean power output (nitrate: 258 ± 28 W; placebo: 257 ± 28 W; P = 0.89) between treatments. Plasma ET-1 increased significantly (P < 0.05) just after exercise in nitrate (4.0 ± 0.8 pg·mL−1) and placebo (2.4 ± 0.4 pg·mL−1) conditions. This increase was significantly greater (P < 0.05) in the nitrate group. Levels of nitrated proteins did not differ between treatments (nitrate: preexercise, 91% ± 23%; postexercise, 81% ± 23%; placebo: preexercise, 95% ± 20%; postexercise, 99% ± 19%).
Conclusion: Sodium nitrate supplementation did not improve a 40-min distance-trial performance in endurance athletes. In addition, concentration of plasma ET-1 increased significantly after exercise after supplementation with sodium nitrate.
1Research Group on Sport Sciences, National Institute of Physical Education (INEFC), University of Barcelona, Barcelona, SPAIN; 2Performance and Health Research Group for High Level Sports, High Performance Center of Barcelona, Sant Cugat, SPAIN; 3Laboratory of Physical Activity Science, Research Group on Community Nutrition and Oxidative Stress, University of the Balearic Islands, Palma de Mallorca, SPAIN; and 4Department of Physiology and Biochemistry, School of Physiotherapy, University of Valladolid, Valladolid, SPAIN
Address for correspondence: Raúl Bescós, Ph.D., Physiology Laboratory, National Institute of Physical Education (INEFC), Av., de l’Estadi s/n, 08038 Barcelona, Spain; E-mail: email@example.com.
Submitted for publication April 2012.
Accepted for publication July 2012.