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

Suzuki T, Morita M, Kobayashi Y, Kamimura A - J Int Soc Sports Nutr (2016)

Bottom Line: This is because NO is a potential modulator of blood flow, muscle energy metabolism, and mitochondrial respiration during exercise.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.

View Article: PubMed Central - PubMed

Affiliation: Healthcare Products Development Center, KYOWA HAKKO BIO CO., LTD., 2, Miyukigaoka, Tsukuba, Ibaraki 305-0841 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.

No MeSH data available.


Related in: MedlinePlus

Study design
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Fig1: Study design

Mentions: The study was conducted at Fukuda Clinic (Osaka, Japan). After enrollment, the subjects were randomized into two groups to receive the following treatments once a day for 1 week before the experimental day in a double-blind fashion: 9 capsules consisting of 2.4 g of L-citrulline (KYOWA HAKKO BIO CO., Ltd., Tokyo, Japan) or 9 placebo capsules consisting of 2.4 g of cornstarch (Nippon NSC Co., Ltd., Tokyo, Japan) before bedtime. The indistinguishability of the capsules was confirmed by the Ethics Committee of Fukuda Clinic (Osaka, Japan). The purity of L-citrulline was analyzed by using an amino acid analyzer (L-8900 Hitachi High-Technologies Corporation, Tokyo, Japan) [23, 24]. There is no recommended dose for L-citrulline intake to enhance sport performance, but a dose of 6 or 8 g of L-citrulline malate has been used in other studies [25, 26]. On the day before each test day, subjects were all given the same meals, which they were required to finish by 9:00 PM; they then fasted overnight. The following morning, blood pressure and heart rate were measured and blood samples were collected. Thereafter, the subjects had breakfast (a rice ball, about 180 kcal) to provide energy 1 h before intake of the 9 capsules of placebo or L-citrulline. After the intake of placebo or L-citrulline, the subjects rested quietly before takingpart in a 4-km cycling time trial (TT). Before the TT, each subject completed a warm-up. The TT was performed on a cycle ergometer (Aerobike 75XL2; Konami Sports & Life Co., Ltd., Tokyo, Japan) [27] 1 h after of the intake of placebo or L-citrulline. After the TT, blood samples were collected from the brachial vein. The study design is summarized in Fig. 1.Fig. 1


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

Suzuki T, Morita M, Kobayashi Y, Kamimura A - J Int Soc Sports Nutr (2016)

Study design
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4759860&req=5

Fig1: Study design
Mentions: The study was conducted at Fukuda Clinic (Osaka, Japan). After enrollment, the subjects were randomized into two groups to receive the following treatments once a day for 1 week before the experimental day in a double-blind fashion: 9 capsules consisting of 2.4 g of L-citrulline (KYOWA HAKKO BIO CO., Ltd., Tokyo, Japan) or 9 placebo capsules consisting of 2.4 g of cornstarch (Nippon NSC Co., Ltd., Tokyo, Japan) before bedtime. The indistinguishability of the capsules was confirmed by the Ethics Committee of Fukuda Clinic (Osaka, Japan). The purity of L-citrulline was analyzed by using an amino acid analyzer (L-8900 Hitachi High-Technologies Corporation, Tokyo, Japan) [23, 24]. There is no recommended dose for L-citrulline intake to enhance sport performance, but a dose of 6 or 8 g of L-citrulline malate has been used in other studies [25, 26]. On the day before each test day, subjects were all given the same meals, which they were required to finish by 9:00 PM; they then fasted overnight. The following morning, blood pressure and heart rate were measured and blood samples were collected. Thereafter, the subjects had breakfast (a rice ball, about 180 kcal) to provide energy 1 h before intake of the 9 capsules of placebo or L-citrulline. After the intake of placebo or L-citrulline, the subjects rested quietly before takingpart in a 4-km cycling time trial (TT). Before the TT, each subject completed a warm-up. The TT was performed on a cycle ergometer (Aerobike 75XL2; Konami Sports & Life Co., Ltd., Tokyo, Japan) [27] 1 h after of the intake of placebo or L-citrulline. After the TT, blood samples were collected from the brachial vein. The study design is summarized in Fig. 1.Fig. 1

Bottom Line: This is because NO is a potential modulator of blood flow, muscle energy metabolism, and mitochondrial respiration during exercise.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.

View Article: PubMed Central - PubMed

Affiliation: Healthcare Products Development Center, KYOWA HAKKO BIO CO., LTD., 2, Miyukigaoka, Tsukuba, Ibaraki 305-0841 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.

No MeSH data available.


Related in: MedlinePlus