Supplementation with Citrulline (Cit) has been shown to have a positive impact on aerobic
exercise performance and related outcomes such as lactate, oxygen uptake (VO2
) kinetics, and the rate
of perceived exertion (RPE), probably due to its relationship to endogenous nitric oxide production.
However, current research has shown this to be controversial. The main objective of this systematic
review and meta-analysis was to analyze and assess the effects of Cit supplementation on aerobic
exercise performance and related outcomes, as well as to show the most suitable doses and timing
of ingestion. A structured literature search was carried out by the PRISMA® (Preferred Reporting
Items for Systematic Reviews and Meta-Analyses) and PICOS guidelines in the following databases:
Pubmed/Medline, Scopus, and Web of Science (WOS). A total of 10 studies were included in the
analysis, all of which exclusively compared the effects of Cit supplementation with those of a placebo
group on aerobic performance, lactate, VO2
, and the RPE. Those articles that used other supplements
and measured other outcomes were excluded. The meta-analysis was carried out using Hedges’ g
random effects model and pooled standardized mean differences (SMD). The results showed no
positive effects of Cit supplementation on aerobic performance (pooled SMD = 0.15; 95% CI (−0.02 to
0.32); I
2
, 0%; p = 0.08), the RPE (pooled SMD = −0.03; 95% CI (−0.43 to 0.38); I
2
, 49%; p = 0.9), VO2
kinetics (pooled SMD = 0.01; 95% CI (−0.16 to 0.17); I
2
, 0%; p = 0.94), and lactate (pooled SMD = 0.25;
95% CI (−0.10 to 0.59); I
2
, 0%; p = 0.16). In conclusion, Cit supplementation did not prove to have
any benefits for aerobic exercise performance and related outcomes. Where chronic protocols seemed
to show a positive tendency, more studies in the field are needed to better understand the effects.
