L-Citrulline for Exercise Performance

Research suggests that L-citrulline supplementation may offer modest benefits for exercise performance, particularly for aerobic endurance and high-intensity cycling in recreationally active and moderately trained individuals, though findings across the available RCTs, systematic reviews, and meta-analyses are notably inconsistent. Studies indicate that chronic supplementation over one to two weeks appears more likely to produce measurable effects — such as improved oxygen uptake kinetics, reduced perceived exertion, and increased work output — than single acute doses, which have repeatedly failed to demonstrate performance benefits in well-trained athletes. The evidence is further complicated by variability in study populations, supplement forms tested (L-citrulline versus citrulline malate versus combination products), and outcome measures used, and at least one well-powered RCT using Bayesian analysis found statistical support for the null hypothesis, meaning the data actively favored no effect rather than simply failing to detect one. Overall, the research base remains limited by small sample sizes, short intervention durations, and a lack of studies in female participants, and reviewers consistently call for larger, more rigorously designed trials before firm conclusions can be drawn.