Oral L citrulline supplementation enhances cycling time trial performance in healthy trained men: Double blind randomized placebo controlled 2 way crossover study
BackgroundMany 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.MethodsA 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.ResultsL 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.ConclusionsOral L citrulline supplementation reduced the time take to complete a cycle ergometer exercise trial.Trial registrationCurrent Controlled Trials UMIN000014278.
Journal of the International Society of Sports Nutrition