The effect of citrulline use on sports performance: Meta-analysis

Citrulline, which is thought to have positive effects on exercise performance by increasing nitric oxide production, is a dietary supplement product that is widely used especially in people doing sports. Citrulline is a non-essential amino acid that is thought to be effective because of its regulatory properties in metabolism and important roles in nitrogen homeostasis. Many researchers have investigated results that may have a positive or negative impact on strength and endurance performance, but complex results have been reported. The aim of this thesis is to determine the limit values on the effects of citrulline support in athletes during exercise to increase the power output-performance by using meta-analysis method and also by compiling the effects on muscle development as well as quality of life. In this study, a comprehensive systematic literature review such as PubMed / Medline, Sciencedirect, Google Scholar and Web of Science was conducted to find peer-reviewed, English, original research studies to evaluate the effect of citrulline supplementation on healthy male and female individuals in high-intensity exercise performances. Independent investigations have been carried out to determine which of the 148 existing scientific studies required for the meta-analysis method and which has been obtained as a result of the literature review, should be included in the method. As a result of these examinations, 12 studies that can be used for analysis were distinguished because they were found suitable for the meta-analysis conditions. A total of 12 independent studies that meet the inclusion criteria to apply the meta-analysis method have been studied in detail. The studies were evaluated under two groups. As a result of the meta-analysis of the seven studies in the first group, the mean differences (MD) (MD, 95% confidence interval (CI)) compared to the model were found as -0.07 (-0.59; 0.44). As a result of the meta-analysis of the five studies in the second group, the mean effects (MD, 95% CI) were found as -0.44 (-1.10; 0.23). The random effects model was determined in the first study (τ2 = 0.2305, I2 = 67%) and in the second study (τ2 = 0.4730, I2 = 88%), since the heterogeneity test was found to be significant in the studies. For meta analysis application performed as a result of the literature review, the average differences of citrulline malate support were calculated as -0.07 for mixed-type performances compared to the placebo group, and -0.44 for explosive strength exercise performances. Although the effect size obtained from the analyzes is observed to be small, the results may be effective on high level athletes, which are determined by the differences of the competition results with small rates. In addition, according to the results of meta analysis, it was determined that citrulline malate support was effective on athletes' blood lactate levels, especially in exercises requiring explosive power.