Highlights: Citrulline supplements are effective in reducing post-exercise rating of perceived exertion (RPE) and muscle soreness. A total of 3-4 g of L-citrulline or 8 g citrulline malate (CM) are recommended 1 h before exercise. Citrulline supplements are especially recommended for power and strength athletes for them to adequately recover and subsequently train at their desired intensity level. Background: Citrulline is one of the non-essential amino acids that is thought to improve exercise performance and reduce post-exercise muscle soreness. We conducted a systematic review and meta-analysis to determine the effect of citrulline supplements on the post-exercise rating of perceived exertion (RPE), muscle soreness, and blood lactate levels. Methods: A random effects model was used to calculate the effect sizes due to the high variability in the study design and study populations of the articles included. A systematic search of PubMed, Web of Science, and ClinicalTrials.gov was performed. Eligibility for study inclusion was limited to studies that were randomized controlled trials involving healthy individuals and that investigated the acute effect of citrulline supplements on RPE, muscle soreness, and blood lactate levels. The supplementation time frame was limited to 2 h before exercise. The types and number of participants, types of exercise tests performed, supplementation protocols for L-citrulline or citrulline malate, and primary (RPE and muscle soreness) and secondary (blood lactate level) study outcomes were extracted from the identified studies. Results: The analysis included 13 eligible articles including a total of 206 participants. The most frequent dosage used in the studies was 8 g of citrulline malate. Citrulline supplementation significantly reduced RPE (n=7, p=0.03) and muscle soreness 24-h and 48-h after post-exercise (n=7, p=0.04; n=6, p=0.25, respectively). However, citrulline supplementation did not significantly reduce muscle soreness 72-h post-exercise (n=4, p=0.62) or lower blood lactate levels (n=8, p=0.17). Conclusion:Citrulline supplements significantly reduced post-exercise RPE and muscle soreness without affecting blood lactate levels.
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