This randomized, double-blind, four-period crossover trial investigates the acute effects of creatine monohydrate, L-arginine, and their combined administration on anaerobic performance, jump performance, and cognitive reaction time in recreationally active adult males. Eighteen healthy male participants complete four experimental conditions in randomized order: placebo, creatine, L-arginine, and creatine plus L-arginine, with at least 72 hours between sessions. Sixty minutes after supplementation, participants perform the Stroop Color-Word Test, countermovement jump test, and Running-Based Anaerobic Sprint Test. Primary outcomes include peak power, average power, countermovement jump height, and incongruent Stroop reaction time. The study aims to determine whether acute co-supplementation produces greater ergogenic and cognitive benefits than either supplement alone or placebo.

Creatine monohydrate and L-arginine are widely used ergogenic supplements that may influence performance through different physiological mechanisms. Creatine contributes to rapid adenosine triphosphate resynthesis through phosphocreatine availability, whereas L-arginine serves as a precursor for nitric oxide synthesis and may enhance blood flow and substrate delivery during exercise. Their combined administration may therefore produce complementary effects on physical and cognitive performance.

This study uses a randomized, double-blind, four-treatment crossover design in recreationally active adult males. Each participant completes four conditions: placebo, creatine monohydrate, L-arginine, and combined creatine plus L-arginine. Sessions are separated by at least 72 hours, and all testing is conducted at the same time of day. Supplementation is administered 60 minutes before performance testing. Creatine is provided as a single acute dose of 0.3 g/kg, L-arginine as 6 g, and the placebo as a matched control beverage.

Outcome assessments include the Running-Based Anaerobic Sprint Test for repeated-sprint power, the countermovement jump test for explosive lower-body performance, and the Stroop Color-Word Test for cognitive reaction time and accuracy. The primary objective is to examine whether acute co-supplementation with creatine and L-arginine improves anaerobic and cognitive outcomes more than placebo or either supplement alone.

Inclusion Criteria:

• Male recreational athletes aged 18 years or older
• At least 2 years of regular participation in organized sport
• Apparently healthy and able to complete high-intensity exercise testing

Exclusion Criteria:

• Known orthopedic, neurological, cardiovascular, pulmonary, or metabolic disorders
• Use of anabolic steroids or performance-enhancing drugs within the previous 3 months
• Use of psychoactive or stimulant substances during the study

An independent researcher prepared coded supplement beverages, and both participants and outcome assessors were blinded to treatment allocation. All drinks were matched for color, flavor, and appearance.