Abstract
BackgroundAthletes are increasingly exploring ways to enhance their physical performance. Increasing blood flow to the working tissues through endothelium-dependent vasodilation is one factor athletes use to realize these results. Sports supplements such as pre-workouts tout this benefit; however, many have not been tested under laboratory conditions to examine the effects of commonly used supplements on vasodilation. Two popular supplements are Nitrosigine® and citrulline malate (CM). Thus, the purpose of this experiment was to determine the effects of Nitrosigine and CM on vasodilation using ultrasound and flow mediated dilation (FMD).MethodsHealthy, normotensive, and physically active male (n = 16) and female (n = 8) young adults participated in the present investigation. We utilized a randomized, double-blind, within-subjects design where participants reported for three trials, each preceded by a 7-day washout period. Baseline FMD measurement was obtained for each visit, followed by consumption of one clinical dose CM (8 g), Nitrosigine (1.5 g), or dextrose placebo (8 g). Following a 60-min digestion period, FMD was repeated. Supplementation order was randomized controlling for potential order effects.ResultsRepeated measures ANOVA yielded a significant supplement (3) x time (2) effect (p < .001), such that Nitrosigine and CM yielded a greater improvement in FMD response than placebo. After supplementation, Nitrosigine and CM increased FMD by 31 and 34%, respectively, compared to a decrease of 2% during the placebo trial. After allometric scaling of the FMD values, supplement x time effect remained significant (p = .001) and changes were similar to non-scaled results. Nitrosigine (23%) and CM (25%) generated significantly greater allometric scaled FMD values when compared to the placebo trial (0.60%).DiscussionBoth Nitrisigine and CM increased endothelial-dependent vasodilation as measured by a change in FMD. Increased vasodilation leads to an increase in skeletal muscle blood flow resulting in potential improvements in exercise performance.
Highlights
Athletes are increasingly exploring ways to enhance their physical performance
A summary of the means, standard deviations, and analysis of variance (ANOVA) results for the flow mediated dilation (FMD) and estimated macronutrient intake data are located in Tables 2 and 3
Post-hoc analysis showed that Nitrosigine and citrulline malate (CM) supplementation resulted in significantly greater increases in FMD% when compared to the placebo trial; there was no significant difference between the two supplements or between sexes (Fig. 2)
Summary
Increasing blood flow to the working tissues through endothelium-dependent vasodilation is one factor athletes use to realize these results. Sports supplements such as pre-workouts tout this benefit; many have not been tested under laboratory conditions to examine the effects of commonly used supplements on vasodilation. The use of ergogenic dietary supplements has become increasingly popular among both recreational and competitive athletes, but the sale and use of such supplements has far outpaced evidence of their effectiveness. Substances that reportedly increase endotheliumdependent nitric oxide (NO) production are among the most commonly included in pre-workout supplement blends. L-arginine must first be metabolized by the liver before entering circulation, rendering it less bioavailable and less effective than other substances at increasing NO production. Inositol-stabilized arginine silicate (Nitrosigine) and L-citrulline, have since replaced L-arginine in many pre-workout supplement
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