This study will examine whether caffeine improves cognitive and competitive performance in professional chess players during tournament-style games. In a randomized double-blind crossover design, participants will complete two experimental sessions in which they consume either caffeinated coffee or decaffeinated coffee before playing a standardized chess match. Cognitive performance will be assessed using attention and reaction-time tests, including the Stroop Test, Trail Making Test, and Puzzle Rush task. Chess performance outcomes such as move accuracy, time management, and error rates will also be evaluated. The study aims to determine whether moderate caffeine intake enhances focus, alertness, and decision-making during prolonged competitive chess play.

This randomized double-blind crossover trial will evaluate the effects of moderate caffeine intake on cognitive and competitive performance in professional chess players. Twelve FIDE-rated chess players will complete two experimental conditions in randomized order: caffeinated coffee and decaffeinated coffee placebo. During each visit, participants will complete standardized cognitive assessments and a tournament-style chess game under controlled laboratory conditions.

Primary outcomes will include objective chess performance metrics derived from chess engine analysis, including move accuracy, centipawn loss, error rates, and time management. Secondary outcomes will include cognitive test performance, tactical reaction time, and self-reported alertness and fatigue. Chess games will be analyzed using standardized software-based evaluation methods.

The crossover design allows each participant to serve as their own control, minimizing variability related to individual differences in skill level, caffeine tolerance, and playing style. The study aims to determine whether caffeine enhances sustained attention, decision-making, and competitive chess performance during prolonged gameplay. Findings may provide insight into nutritional strategies for cognitive performance optimization in mentally demanding competitive environments.

Inclusion Criteria:

• Male and female professional chess players aged 18-50 years
• Current Fédération Internationale des Échecs (FIDE) standard rating between 2300 and 2600 Elo, or achievement of a standard FIDE rating within this range during the previous 12 months
• Habitual caffeine consumers consuming ≤2 cups of coffee per day
• Willingness to comply with all study procedures and study visits
• Ability to provide written informed consent

Exclusion Criteria:

• Non-caffeine users
• Habitual caffeine intake exceeding 2 cups of coffee per day
• Cardiovascular disorders
• Metabolic disorders
• Psychiatric disorders
• Pregnancy or breastfeeding
• Current smoking
• Shift workers
• Use of psychoactive medications
• Participation in another clinical trial within the previous 3 months
• Known allergy or intolerance to milk proteins, dairy products, or soy
• Known red-green color blindness or other color vision deficiencies that may interfere with Stroop Test performance

Individual participant data (IPD) will not be publicly shared because this is a small pilot study involving highly specialized professional chess players, and there is potential risk of participant identification despite de-identification procedures.

The caffeinated and decaffeinated coffee beverages will be prepared and coded by a designated research team member who is not involved in participant testing, cognitive assessments, gameplay supervision, or outcome analysis. Participants, investigators, and outcome assessors will remain blinded to intervention assignment until completion of data analysis.