Background: Ergogenic nutritional supplementation is sought by professional athletes for improving physical performance; nevertheless, scientific evidence to support the chronic use of L-Arginine among water polo players is missing.
Methods: Seventeen male professional water polo players were randomly assigned to assume 5 grams per day of L-Arginine ( = 9) or placebo ( = 8) for 4 weeks. The players' fitness level was assessed in the maximal speed swimming test.