Abstract
PurposeOral l-citrulline (Cit) increases plasma l-arginine (Arg) concentration and the production of nitric oxide (NO). NO dilates blood vessels and potentially improves sports performance. The combination of oral Arg and Cit (Arg + Cit) immediately and synergistically increases plasma Arg and nitrite/nitrate (NOx) concentrations more than either Cit or Arg alone. This prompted us to assess the effects of oral Arg + Cit on 10-min cycling performance in a double-blind, randomized, placebo-controlled crossover trial.MethodsTwenty-four male soccer players ingested either Cit + Arg or placebo (both 1.2 g/day each) for 6 days. On day 7, they ingested Cit + Arg 1 h before performing a 10-min full-power pedaling test on a bicycle ergometer. Plasma NOx and amino acid levels were measured before and after the test, as well as the participants’ subjective perception of physical exertion.ResultsPower output was significantly greater with Cit + Arg than in the placebo group (242 ± 24 vs. 231 ± 21 W; p < 0.05). Plasma concentrations of post-exercise NOx (p < 0.05), Cit (p < 0.01) and Arg (p < 0.01) were significantly higher in the Cit + Arg than in the placebo group, whereas exercise upregulated plasma NOx concentrations in both groups (p < 0.05). Cit + Arg also gave improved post-exercise subjective perception of “leg muscle soreness” and “ease of pedaling” (both p < 0.05).ConclusionSeven days of oral Citrulline (1.2 g/d) and Arginine (1.2 g/d) ingestion improved 10-min cycling performance and the perception of physical exertion in male collegiate soccer players.
Highlights
Nitric oxide (NO) dilates blood vessels, enhancing circulation and improving mitochondrial efficiency (Albrecht et al 2003; Tschakovsky and Joyner 2008; Larsen et al 2011)
We have recently demonstrated that Cit supplementation exhibits several beneficial effects on the cardiovascular system and endothelial function by enhancing NO production (Ochiai et al 2012; Yabuki et al 2013)
A comparison of plasma Cit and Arg levels before and after the exercise showed that plasma Cit levels did not change after the test in the placebo group, whereas plasma Cit (35.7 ± 1.4–147.4 ± 7.5 μM; p < 0.01) and Arg (96.9 ± 5.0–158.5 ± 6.1 μM; p < 0.01) levels were significantly higher in the Cit + Arg group post-exercise (Fig. 2b, c)
Summary
Nitric oxide (NO) dilates blood vessels, enhancing circulation and improving mitochondrial efficiency (Albrecht et al 2003; Tschakovsky and Joyner 2008; Larsen et al 2011). In. European Journal of Applied Physiology (2019) 119:1075–1084 addition, NO exerts a range of physiological functions [e.g., enhancing muscle contractile efficiency, improving exercise tolerance, and regulating oxygen consumption (Shen et al 1994; Larsen et al 2007; Bailey et al 2010; Petróczi and Naughton 2010; Lansley et al 2011a; Bescós et al 2012; Jones et al 2013)] acting as an intercellular messenger as well as forming reactive nitrogen species (Quijano et al 2016). Some researchers have focused on the beneficial effects that dietary nitrate (NO3−)-containing supplements, such as beetroot juice, have on exercise performance (Bailey et al 2009; Lansley et al 2011b; Cermak et al 2012a; Wilkerson et al 2012; Jones 2014). Efforts have been directed towards strategies that promote NO production
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