Acute Effects of Combined and Isolated Caffeine and Theanine Supplementation on Physical and Cognitive Performance in Competitive Athletes: A Randomized, Double-Blind, Placebo-Controlled Crossover Study
试验速览
- 阶段
- 不适用
- 状态
- 已完成
- 发起方
- 入组人数
- 20
- 试验地点
- 2
- 主要终点
- Total Distance Covered in the Yo-Yo Intermittent Endurance Test Level 1 (meters)
研究概览
简要总结
The aim of this clinical trial is to examine how caffeine and L-theanine, taken alone or together, affect both physical and cognitive performance in healthy, trained athletes. The study aims to answer whether these commonly consumed dietary ingredients can enhance strength, endurance, and hand-eye coordination under controlled laboratory conditions.
Researchers will compare four supplementation conditions:
Caffeine (CAF) - 3 mg per kilogram of body weight L-Theanine (THE) - 200 mg Combined Caffeine and L-Theanine (COM) - same doses together Placebo (CON) - mannitol (inactive substance) Each participant will complete all four test sessions in a randomized, double-blind, crossover design, with at least 72 hours between sessions. Capsules will be taken 60 minutes before testing to allow time for absorption. During each session, participants will perform a series of physical and cognitive tasks, including maximal isometric strength tests, an intermittent endurance test, and a computerized eye-hand coordination task.
The main hypothesis is that caffeine and L-theanine, alone or in combination, will improve strength and cognitive coordination compared with placebo. All participants are healthy competitive athletes between 18 and 30 years old. The study is conducted under standardized laboratory and indoor sports-hall conditions, with ethics approval obtained from the Sinop University Human Research Ethics Committee (Approval No. 2025/337).
详细描述
This randomized, double-blind, placebo-controlled, crossover clinical trial investigates the acute effects of caffeine (CAF), L-theanine (THE), their combination (COM), and placebo (CON) supplementation on physical and cognitive performance in young, healthy, competitive athletes. Each participant completed all four experimental conditions in randomized order, separated by a minimum 72-hour washout period to minimize carryover effects. The randomization sequence was computer-generated by an independent researcher, and both participants and assessors were blinded to all conditions.
A total of 20 trained athletes (12 males, 8 females; 19.9 ± 2.4 years) participated. All were actively engaged in team or individual sports at a competitive level, with no history of cardiovascular, neurological, or musculoskeletal disorders, and no known intolerance to caffeine, theanine, or placebo components. Anthropometric and body composition data were collected using standardized procedures, including multi-frequency bioelectrical impedance analysis. Participants maintained normal caffeine consumption habits to preserve ecological validity and avoid withdrawal effects.
The supplementation protocol consisted of four conditions: (1) 3 mg/kg anhydrous caffeine, (2) 200 mg L-theanine, (3) a combination of both, and (4) placebo (mannitol). All supplements were encapsulated in visually identical gelatin capsules, and participants ingested five capsules with water 60 minutes before testing. Testing sessions were conducted at 09:00 a.m. to minimize circadian variability. Participants abstained from alcohol, strenuous exercise, and dietary supplements for 24 hours before each session, and replicated their pre-trial dietary intake based on 24-hour dietary logs.
All testing sessions were performed under standardized indoor laboratory conditions (22 ± 1 °C, 50 ± 5% humidity). The test sequence was fixed as eye-hand coordination, maximal isometric strength, and intermittent aerobic endurance, with adequate rest intervals between tests.
Primary outcomes included:
研究设计
- 研究类型
- Interventional
- 分配方式
- Randomized
- 干预模型
- Crossover
- 主要目的
- Basic Science
- 盲法
- Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
入排标准
- 年龄范围
- 18 Years 至 30 Years（Adult）
- 性别
- All
- 接受健康志愿者
- 是
入选标准
- •Active participation in individual or team sports at a competitive level
- •Age between [insert range, e.g., 18-30] years
- •Absence of any known medical or metabolic disorder
排除标准
- •History of cardiovascular, neurological, or musculoskeletal disorders within the past 12 months
- •Known intolerance or hypersensitivity to caffeine or theanine
- •Allergy to mannitol or other excipients used in capsule formulation
- •Current use of prescription medications
- •Physician-directed restriction of caffeine or theanine consumption.
结局指标
主要结局
Total Distance Covered in the Yo-Yo Intermittent Endurance Test Level 1 (meters)
时间窗: 60 minutes post-supplement ingestion.
Distance (m) completed during the Yo-Yo Intermittent Endurance Test Level 1 following standard protocol.
Peak Handgrip Force (kgf)
时间窗: 60 minutes post-supplement ingestion.
Highest handgrip force obtained from three maximal voluntary contractions using a calibrated digital dynamometer.
Peak Leg Extension Force (kgf)
时间窗: 60 minutes post-supplement ingestion.
Highest value from three maximal voluntary contractions measured using a leg dynamometer.
Peak Back Extension Force (kgf)
时间窗: 60 minutes post-supplement ingestion.
Highest value from three maximal voluntary contractions measured with a back strength dynamometer.
Eye-Hand Coordination Fast Speed Reaction Time (EHC-FS)
时间窗: 60 minutes post-supplement ingestion.
Reaction time (milliseconds) during the fast-speed EHC trial.
Eye-Hand Coordination Accuracy (EHC-A)
时间窗: 60 minutes post-supplement ingestion.
Accuracy percentage (%) obtained from the computerized eye-hand coordination test battery.
Eye-Hand Coordination Slow Speed Reaction Time (EHC-SS)
时间窗: 60 minutes post-supplement ingestion.
Reaction time (milliseconds) during the slow-speed EHC trial.
Eye-Hand Coordination Distance From Ball Center (EHC-DFBC)
时间窗: 60 minutes post-supplement ingestion.
Mean deviation from target center measured during coordination task.
次要结局
未报告次要终点
研究者
Ulaş Can YILDIRIM
Assoc. Prof.
Sinop University