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Randomized Controlled Trial
. 2016 Feb 19:13:6.
doi: 10.1186/s12970-016-0117-z. eCollection 2016.

Oral L-citrulline supplementation enhances cycling time trial performance in healthy trained men: Double-blind randomized placebo-controlled 2-way crossover study

Takashi Suzuki  1 , Masahiko Morita  1 , Yoshinori Kobayashi  2 , Ayako Kamimura  1
Affiliations
Randomized Controlled Trial

Oral L-citrulline supplementation enhances cycling time trial performance in healthy trained men: Double-blind randomized placebo-controlled 2-way crossover study

Takashi Suzuki et al. J Int Soc Sports Nutr. .

Abstract

Background: Many human studies report that nitric oxide (NO) improves sport performance. This is because NO is a potential modulator of blood flow, muscle energy metabolism, and mitochondrial respiration during exercise. L-Citrulline is an amino acid present in the body and is a potent endogenous precursor of L-arginine, which is a substrate for NO synthase. Here, we investigated the effect of oral L-citrulline supplementation on cycling time trial performance in humans.

Methods: A double-blind randomized placebo-controlled 2-way crossover study was employed. Twenty-two trained males consumed 2.4 g/day of L-citrulline or placebo orally for 7 days. On Day 8 they took 2.4 g of L-citrulline or placebo 1 h before a 4-km cycling time trial. Time taken to complete the 4 km cycle, along with power output/VO2 ratio (PO/VO2), plasma nitrite and nitrate (NOx) and amino acid levels, and visual analog scale (VAS) scores, was evaluated.

Results: L-Citrulline supplementation significantly increased plasma L-arginine levels and reduced completion time by 1.5 % (p < 0.05) compared with placebo. Moreover, L-citrulline significantly improved subjective feelings of muscle fatigue and concentration immediately after exercise.

Conclusions: Oral L-citrulline supplementation reduced the time take to complete a cycle ergometer exercise trial.

Trial registration: Current Controlled Trials UMIN000014278.

Keywords: Ergogenic; Human; L-Citrulline; Nitric oxide (NO); Sport performance.

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Figures

Fig. 1
Fig. 1
Study design
Fig. 2
Fig. 2
Changes in plasma NOx before and after a 4 km TT. Values are means ± S.E.M. n = 22
Fig. 3
Fig. 3
Completion times of the 4 km TT after placebo or L-citrulline supplementation. Values are means ± S.E.M. n = 22, * p < 0.05, indicating a significant difference from placebo
Fig. 4
Fig. 4
PO profile during the 4 km TT (a) and mean PO (b) of the 4 km TT after placebo or L-citrulline supplementation. Values are means ± S.E.M. n = 22. * p < 0.05, indicating a significant difference from placebo
Fig. 5
Fig. 5
PO/VO2 during the 4 km TT after placebo or L-citrulline supplementation. Values are means ± S.E.M. n = 22
Fig. 6
Fig. 6
Subjective feelings immediately after exercise. Values are means ± S.E.M. n = 22. * p < 0.05, indicating a significant difference from placebo
See this image and copyright information in PMC

References

    1. Albrecht EW, Stegeman CA, Heeringa P, Henning RH, Van Goor H. Protective role of endothelial nitric oxide synthase. J Pathol. 2003;199:8–17. doi: 10.1002/path.1250. - DOI - PubMed
    1. Petroczi A, Naughton DP. Potentially fatal new trend in performance enhancement: a cautionary note on nitrite. J Int Soc Sports Nutr. 2010;7:25. doi: 10.1186/1550-2783-7-25. - DOI - PMC - PubMed
    1. Bescos R, Sureda A, Tur JA, Pons A. The effect of nitric-oxide-related supplements on human performance. Sports Med. 2012;42:99–117. doi: 10.2165/11596860-000000000-00000. - DOI - PubMed
    1. Jones AM. Dietary nitrate supplementation and exercise performance. Sports Med. 2014;44(Suppl 1):S35–45. doi: 10.1007/s40279-014-0149-y. - DOI - PMC - PubMed
    1. Shen W, Xu X, Ochoa M, Zhao G, Wolin MS, Hintze TH. Role of nitric oxide in the regulation of oxygen consumption in conscious dogs. Circ Res. 1994;75:1086–95. doi: 10.1161/01.RES.75.6.1086. - DOI - PubMed

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