Acute Citrulline-Malate Supplementation and High-Intensity Cycling Performance.
Level 2 - randomized trial
Randomized, double-blind, placebo-controlled crossover trial in humans
PubMed 26808848 · doi:10.1519/JSC.0000000000001338
What was done
In a double-blind, placebo-controlled crossover trial, 10 well-trained males ingested either 12 g of citrulline-malate (in 400 ml) or a sugar-free cordial placebo 60 minutes before testing. The exercise protocol comprised 10 repeated maximal cycle sprints (15 seconds on, 30 seconds rest) followed by 5 minutes of recovery and a cycling time-to-exhaustion test at 100% peak power. Plasma amino acids, heart rate, power output, time to exhaustion, rating of perceived exertion, gastrointestinal symptoms, and blood acid-base markers were measured.
What was found
Citrulline-malate ingestion caused significant plasma increases in citrulline (8.8-fold), ornithine (3.9-fold), and glutamine (1.3-fold) after 60 minutes (p ≤ 0.05), with no gastrointestinal side effects reported. Exercise heart rate was significantly higher in the citrulline-malate trial compared to placebo. However, no significant differences (p > 0.05) were found between trials for time to exhaustion (120 ± 61 s citrulline-malate vs. 113 ± 50 s placebo), peak power, mean power, power fatigue index (36 ± 16% vs. 28 ± 18%), rating of perceived exertion, or acid-base parameters including blood pH, lactate, bicarbonate, and base excess.
Why it matters
Despite substantial increases in circulating amino acids and a higher exercise heart rate, high-dose acute citrulline-malate did not enhance repeated sprint capacity, anaerobic endurance, or buffering capacity in trained athletes.
Limits
The study was limited by a very small sample size (n = 10) consisting solely of well-trained males, preventing generalization to females or untrained individuals. It tested only an acute single-dose protocol (12 g taken 60 minutes prior) under a specific cycling sprint-and-exhaustion model, leaving chronic supplementation effects unmeasured.
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- contradicts Gastrointestinal distress is a well-documented side effect of beetroot and citrulline supplementation.