Study of Different Caffeine Supplementation Strategies on Resistance Training-Induced Adaptations
试验速览
- 阶段
- 不适用
- 状态
- 已完成
- 发起方
- 入组人数
- 120
- 试验地点
- 1
- 主要终点
- Change in Lean Body Mass Measured by DXA
研究概览
简要总结
This parallel-group, randomized, double-blind, placebo-controlled trial investigates the effects of three different caffeine supplementation strategies on resistance training-induced adaptations in 120 caffeine-naive, inactive young adult males. Participants will undergo a 10-week supervised resistance training program. The four supplementation strategies are: (1) constant daily low-moderate dosing (4 mg/kg/day), (2) gradually escalating dose (2 to 6 mg/kg across weeks), (3) training-day-only caffeine (4 mg/kg/day), and (4) placebo. Primary outcomes include maximal strength, body composition (lean body mass and fat mass), skeletal muscle thickness, and training volume progression. Secondary outcomes include muscular endurance, jump height, flight-time-to-contraction-time (FT:CT) ratio, mechanistic/biological variables (epinephrine, norepinephrine, cortisol, testosterone, creatine kinase, IGF-1), rate of perceived exertion, sleep/recovery parameters, and adverse effects.
详细描述
BACKGROUND: Caffeine is a well-established acute ergogenic aid that reliably improves endurance, power, and resistance-exercise performance when consumed at typical ergogenic doses (approximately 2-6 mg/kg about 60 minutes pre-exercise). However, whether caffeine exerts direct biological effects on muscle protein balance and hypertrophy remains unclear. Regular caffeine ingestion produces partial physiological tolerance, creating the possibility that chronic supplementation elicits different outcomes than acute dosing. OBJECTIVES: This study addresses three translational questions: (1) Does constant daily low-moderate dosing potentiate training adaptations? (2) Does a gradually escalating dose strategy produce greater effects by overcoming tolerance? (3) Does training-day-only caffeine preserve acute ergogenic effects while limiting tolerance and sleep disturbance? METHODS: 120 caffeine-naive, physically inactive young adult males aged 18-30 years will be randomly assigned to one of the following groups (n=30 per group): (1) constant daily low-moderate dosing (CON, 4 mg/kg/day), (2) gradually escalating dose (ESC, 2 to 6 mg/kg across weeks), (3) training-day-only caffeine (TDO, 4 mg/kg/day), and (4) placebo (PLA). All participants will undergo supervised resistance training 3 times per week. OUTCOMES: Primary endpoints include maximal strength, body composition (lean body mass and fat mass), skeletal muscle thickness, and training volume metrics. Secondary outcomes include muscular endurance, jump height, flight-time-to-contraction-time (FT:CT) ratio, mechanistic/biological variables (epinephrine, norepinephrine, cortisol, testosterone, creatine kinase, IGF-1), rate of perceived exertion, sleep/recovery parameters, and adverse effects. STATISTICAL ANALYSIS: Linear Mixed Models will be used to analyze the data.
研究设计
- 研究类型
- Interventional
- 分配方式
- Randomized
- 干预模型
- Parallel
- 主要目的
- Basic Science
- 盲法
- Triple (Participant, Investigator, Outcomes Assessor)
盲法说明
Caffeine and placebo supplements are identical in appearance, taste, and packaging. Supplements are pre-packaged and coded by an independent pharmacist not involved in the study. Neither participants, investigators conducting training sessions and assessments, nor outcome assessors analyzing DXA scans, performance tests, and blood samples will know group assignments. Unblinding will occur only after database lock and completion of statistical analysis.
入排标准
- 年龄范围
- 18 Years 至 30 Years（Adult）
- 性别
- Male
- 接受健康志愿者
- 是
入选标准
- •Male sex and age between 18 and 30 years
- •Daily caffeine intake <100 mg/day
- •resistance-training experience ≥1 year and <3 years
- •Body mass index (BMI) between 18.5-25 kg/m2
- •Willingness to attend all training and testing sessions regularly
- •Provision of written informed consent after being fully informed about the study
排除标准
- •Presence of cardiovascular, metabolic, renal, hepatic, or other serious chronic diseases
- •Diagnosed psychiatric disorders or severe caffeine intolerance/allergy
- •Use of medications affecting caffeine metabolism or muscle anabolism (e.g., beta-blockers, antidepressants, anabolic steroids)
- •Musculoskeletal injuries that prevent safe resistance training
- •Smoking or alcohol consumption at levels that could affect study outcomes
- •Concurrent participation in another exercise intervention study
- •Inability to tolerate DXA scanning or blood sampling
研究组 & 干预措施
Strategy 1: Constant Daily Dose
Participants receive caffeine at a constant daily dose of 4 mg/kg/day for 10 weeks. Supervised resistance training is performed 3 times per week for 10 weeks.
干预措施: Caffeine (Constant Daily Dose) (Dietary Supplement)
Strategy 2: Escalating Dose
Participants receive caffeine at a gradually escalating dose, starting at 2 mg/kg/day in week 1 and increasing to 6 mg/kg/day by week 10 (1 mg/kg every 2 weeks). Supervised resistance training is performed 3 times per week for 10 weeks.
干预措施: Caffeine (Escalating Dose) (Dietary Supplement)
Strategy 3: Training Days Only
Participants receive caffeine at 4 mg/kg only on training days (3 times per week) for 10 weeks. Supervised resistance training is performed 3 times per week for 10 weeks.
干预措施: Caffeine (Training Days Only) (Dietary Supplement)
Placebo
Participants receive 250 mg/day cellulose for 10 weeks. Supervised resistance training is performed 3 times per week for 10 weeks.
干预措施: placebo capsule (Dietary Supplement)
结局指标
主要结局
Change in Lean Body Mass Measured by DXA
时间窗: Baseline and post-test (after completing 10 weeks of interventions)
Change in total lean body mass measured using dual-energy X-ray absorptiometry (DXA), reported in kilograms.
Change in Fat Mass Measured by DXA
时间窗: Baseline and post-test (after completing 10 weeks of interventions)
Change in fat mass measured using DXA.
Maximal Strength
时间窗: Baseline, and post-test (after completing 10 weeks of interventions)
Measure by one-repetition maximum (1-RM) on a lower body (Smith machine Back Squat) and two upper body (Bench Press machine and Lat Pulldown machine) exercises.
Total Training Volume Load
时间窗: During the intervention period (all training sessions).
Total training volume load calculated as the sum of lifted load using the formula (kilograms × repetitions × sets) accumulated during each intervention period.
Change in Skeletal Muscle Thickness
时间窗: Baseline and post-test (after completing 10 weeks of interventions)
Change in skeletal muscle thickness measured using B-mode ultrasound, reported in mm.
Change in Plasma Proteomic Fractional Synthesis Rate (FSR)
时间窗: Baseline; End of Intervention Period 1 (Week 4); End of Intervention Period 2 (Week 4)
Change in plasma proteomic fractional synthesis rate (FSR) calculated using the deuterium oxide (D2O) method. This physiological parameter will be reported as an indicator of integrated muscle protein synthesis.
Change in Lean Body Mass Measured by DXA
时间窗: Baseline; End of Intervention Period 1 (Week 4); End of Intervention Period 2 (Week 4)
Change in total lean body mass measured using dual-energy X-ray absorptiometry (DXA), reported in kilograms.
Change in Muscle Volume Measured by DXA
时间窗: Baseline; End of Intervention Period 1 (Week 4); End of Intervention Period 2 (Week 4)
Change in muscle volume calculated based on regional muscle measurements obtained using DXA.
Change in Maximal Strength Assessed by 1RM/3RM Tests
时间窗: Baseline; End of Intervention Period 1 (Week 4); End of Intervention Period 2 (Week 4)
Change in maximal strength assessed using one-repetition maximum (1RM) or three-repetition maximum (3RM) tests performed in the bench press and squat exercises.
Total Training Volume Load
时间窗: Intervention Period 1 (Weeks 1-4); Intervention Period 2 (Weeks 1-4)
Total training volume load calculated as the sum of lifted load using the formula (kilograms × repetitions × sets) accumulated during each intervention period.
次要结局
- Muscular endurance(Baseline, and post-test (after completing 10 weeks of interventions))
- Neuromuscular function(Baseline and post-test (after completing 10 weeks of interventions))
- Resting concentrations of testosterone(Baseline, and post-test (after completing 10 weeks of interventions))
- Plasma epinephrine responses to exercise(During the first training session of Week 1 and the final training session of Week 10, at three time points: (1) pre-supplementation, (2) immediately before exercise and (3) immediately after exercise.)
- Recovery(Before each of the 30 training sessions during the study.)
- Adverse Events(From initiation of the 4-week caffeine abstinence period through completion of the post-intervention assessments, monitored throughout the study (approximately 16 weeks).)
- Sleep quality(Baseline and post-test (after completing 10 weeks of interventions).)
- Rate of perceived exertion(After each supervised training session, participants were assessed throughout the 10-week intervention period (30 training sessions).)
- Resting concentrations of insulin-like growth factor-1 (IGF-1)(Baseline, and post-test (after completing 10 weeks of interventions))
- Resting concentrations of cortisol(Baseline, and post-test (after completing 10 weeks of interventions))
- Resting concentrations of creatine kinase(Baseline, and post-test (after completing 10 weeks of interventions))
- Serum cortisol responses to exercise(During the first training session of Week 1 and the final training session of Week 10, at three time points: (1) pre-supplementation, (2) immediately before exercise and (3) immediately after exercise.)
- Plasma norepinephrine responses to exercise(During the first training session of Week 1 and the final training session of Week 10, at three time points: (1) pre-supplementation, (2) immediately before exercise and (3) immediately after exercise.)
- Change in Serum Hormonal Concentrations(Baseline; Week 2; End of Intervention Period 1 (Week 4); Baseline; Week 2; End of Intervention Period 2 (Week 4))
- Self-Reported Sleep Quality Score(Weekly during Intervention Period 1 (Weeks 1-4); Weekly during Intervention Period 2 (Weeks 1-4))
- Subjective Recovery Score Assessed by Likert Scale(After each supervised training session during Intervention Period 1; After each supervised training session during Intervention Period 2)
- Adverse Events(Throughout the entire study duration (8 weeks))
研究者
Abdullah Demirli
Assistant Professor
Istanbul University - Cerrahpasa