The Acute Effects of Arginine Supplementation on Vasodilatation, Nitric Oxide Production and Muscle Performance

Abstract

Nutritional supplements based on the amino acid arginine (Arg) have been used mainly by recreational resistance exercise trained subjects, under the claim that improvements will occur in muscle performance due to an increase on nitric oxide (NO) and on blood flow to muscles in exercise. However, NO supplementations studies have demonstrated controversial results in literature. PURPOSE: To evaluate the effects of supplementation with Arg on vasodilatation, NO production, and muscle performance in recreational resistance exercise (RE) trained man. METHODS: Sixteen subjects (18 - 29 years), randomly assign to 4 days of oral supplementation (3.2 - 9.6 g/day) of Arg or placebo (Pla) in a double blind crossover design, with washout of 2 weeks between phases. They were submitted to 3 sets of biceps curl with 65% of 1RM (maximum repetition) when blood lactate (LAC) and vascular parameters were measured by EcoDoppler on the right bracquial artery (arterial diameter - mean of longitudinal and transversal measures - AD, velocity time integral - VTI, peak systolic ventricular - PSV, vascular resistance - RI, systolic flow index - SFI), at rest, after occlusion, post-exercise biceps curl (1, 5 and 10 min). NO production was estimated by nitrite serum post exercise. The muscular performance and fatigue ratio were measured by the maximum number of repetitions in the 3 bout of exercise. RESULTS: Almost all vascular parameters (DA, PSV, VTI, SFI, RI) and LAC differed from the rest of other periods for both groups (P<0.05), although the SFI and RI did not differ from rest to post-occlusion on Pla and Arg group, respectively. The ANOVA with repeated measures showed no significant differences between Arg and Pla groups when compared the mean vascular parameters registered, except for AD on post-exercise 1 min (AD: PLA= 0.434 ± 0.035; Arg= 0.446 ± 0.036; p= 0.023). No effect of Arg was found in muscle performance from number of exercise repetitions, or LAC and NO production. The short period supplementation of oral Arg does not result in vascular changes, improvement in RE muscle performance, or increased production of NO. CONCLUSIONS: Although long-term studies are needed to better elucidate these mechanisms, our findings suggest no ergogenic effects of Arg supplementation in recreational resistance exercise trained men.