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To assess the effect of diet enrichment with L-arginine or supplementation at high doses on physiological adaptation during exercise, 9 athletes followed 3 different diets, each over 3 consecutive days, with a wash-out period of 4 d between training sessions: control diet (CD), 5.5 ± 0.3 g/d of L-arginine; Diet 1 (rich in L-arginine food), 9.0 ± 1.1 g/d of L-arginine; and Diet 2 (the same as CD but including an oral supplement of 15 g/d), 20.5 ± 0.3 g/d of L-arginine. Plasma nitrate levels of each participant were determined on the day after each treatment. Participants performed a submaximal treadmill test (initial speed 10–11 km/hr, work increments 1 km/hr every 4 min until 85–90% VO2max, and passive recovery periods of 2 min). Oxygen uptake and heart rate were monitored throughout the test. Blood lactate concentration ([La]b) was determined at the end of each stage. Repeated-measures ANOVA and paired Student’s t tests were used to compare the various physiological parameters between diets. The level of significance was set at p < .05. [La]b showed a significant effect at the 5-min time point between CD and Diet 2 (CD 3.0 ± 0.5 mM, Diet 2 2.5 ± 0.5 mM, p = .03), but this tendency was not found at higher exercise intensities. No significant differences were observed in any of the cardiorespiratory or plasma nitrate levels. In conclusion, dietary L-arginine intake on the days preceding the test does not improve physiological parameters during exercise.

Bescós and Esteve are with the Physiology Laboratory, National Institute of Physical Education, Barcelona, Spain. Gonzalez-Haro is with the Pharmacology and Physiology Dept., University of Zaragoza. Pujol, Drobnic, Ruiz, and Galilea are with the Physiology and Nutrition Dept., High Performance Center, Barcelona, Spain. Alonso and Santolaria are with the Dept. of Biochemistry and Molecular Biology, University of Valencia, Valencia, Spain.