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J Int Soc Sports Nutr. 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.

Author information

1
Healthcare Products Development Center, KYOWA HAKKO BIO CO., LTD., 2, Miyukigaoka, Tsukuba, Ibaraki 305-0841 Japan.
2
Laboratory of Pharmacognosy, School of Pharmaceutical Sciences, Kitasato University, 5-9-1, Shirokane, Minato-ku, Tokyo, 108-0861 Japan.

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

PMID:
26900386
PMCID:
PMC4759860
DOI:
10.1186/s12970-016-0117-z
[Indexed for MEDLINE]
Free PMC Article

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