Effect of isolated and combined ingestion of caffeine and citrulline malate on resistance exercise and jumping performance: a randomized double-blind placebo-controlled crossover study

This randomized, double-blind, placebo-controlled crossover study investigated the isolated and combined effects of caffeine (5 mg/kg) and citrulline malate (12 g) on muscular performance in 35 resistance-trained participants. Compared to placebo, caffeine alone and caffeine combined with citrulline malate significantly enhanced 1RM bench press strength and muscular endurance in the squat and bench press. Citrulline malate alone had no ergogenic effect on any outcome. No significant differences were found for jump variables, squat strength, or pain perception. Seven adverse events were reported, all during the combined supplement condition. The study suggests caffeine is ergogenic for strength and endurance, but adding citrulline malate does not enhance these effects. Limitations include the lack of plasma concentration measurements and potential influence of habitual caffeine intake.