Resistance Training Adaptations and Caffeine Intake

NCT07410195 | Completed

• 1 other identifier: 2026/01-1792
• Study Type: interventional
• Target: 120
• Locations: 1 country
• Sites: 1

Brief Summary

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.

Conditions

Muscle Hypotrophy; Exercise Performance; Muscle Strength; Adaptation

Keywords

Caffeine; Resistance Training; Muscle Adaptation; Supplementation; Strength Training; Hypertrophy

Outcome Measures

Primary Outcomes (5)

• Change in Lean Body Mass Measured by DXA

  Change in total lean body mass measured using dual-energy X-ray absorptiometry (DXA), reported in kilograms.

  Baseline and post-test (after completing 10 weeks of interventions)

• Change in Fat Mass Measured by DXA

  Change in fat mass measured using DXA.

  Baseline and post-test (after completing 10 weeks of interventions)

• Maximal Strength

  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.

  Baseline, and post-test (after completing 10 weeks of interventions)

• Total Training Volume Load

  Total training volume load calculated as the sum of lifted load using the formula (kilograms × repetitions × sets) accumulated during each intervention period.

  During the intervention period (all training sessions).

• Change in Skeletal Muscle Thickness

  Change in skeletal muscle thickness measured using B-mode ultrasound, reported in mm.

  Baseline and post-test (after completing 10 weeks of interventions)

Secondary Outcomes (13)

• 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.

Study Arms (4)

Strategy 1: Constant Daily Dose

EXPERIMENTAL

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.

Dietary Supplement: Caffeine (Constant Daily Dose)

Strategy 2: Escalating Dose

EXPERIMENTAL

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.

Dietary Supplement: Caffeine (Escalating Dose)

Strategy 3: Training Days Only

EXPERIMENTAL

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.

Dietary Supplement: Caffeine (Training Days Only)

Placebo

PLACEBO COMPARATOR

Participants receive 250 mg/day cellulose for 10 weeks. Supervised resistance training is performed 3 times per week for 10 weeks.

Dietary Supplement: placebo capsule

Interventions

Caffeine (Constant Daily Dose) DIETARY_SUPPLEMENT

Oral caffeine capsule at 4 mg/kg body weight, consumed daily approximately 60 minutes before training sessions (on training days) or at the same time of day (on rest days).

Strategy 1: Constant Daily Dose

Caffeine (Escalating Dose) DIETARY_SUPPLEMENT

• Oral caffeine starting at 2 mg/kg/day and increasing incrementally to reach 6 mg/kg/day by week 10.

Strategy 2: Escalating Dose

Caffeine (Training Days Only) DIETARY_SUPPLEMENT

Oral caffeine capsule at 4 mg/kg body weight, consumed only on training days approximately 60 minutes before exercise.

Strategy 3: Training Days Only

placebo capsule DIETARY_SUPPLEMENT

Oral placebo capsule (250 mg cellulose), consumed daily approximately 60 minutes before training sessions (on training days) or at the same time of day (on rest days).

Placebo

Eligibility Criteria

• Age: 18 Years - 30 Years
• Gender Eligibility Details: Individuals who were assigned male at birth and identify as male.
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• 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

You may not qualify if:

• 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

Sponsors & Collaborators

• Istanbul University - Cerrahpasa: lead
• İstanbul Yeni Yüzyıl Üniversitesi: collaborator

Study Sites (1)

Istanbul University-Cerrahpasa, Faculty of Sport Sciences Performance Laboratory

Istanbul, Avcilar, 34010, Turkey (Türkiye)

Location

Related Publications (7)

• Lovallo WR, Whitsett TL, al'Absi M, Sung BH, Vincent AS, Wilson MF. Caffeine stimulation of cortisol secretion across the waking hours in relation to caffeine intake levels. Psychosom Med. 2005 Sep-Oct;67(5):734-9. doi: 10.1097/01.psy.0000181270.20036.06.

  PMID: 16204431 BACKGROUND

• Matsumura T, Takamura Y, Fukuzawa K, Nakagawa K, Nonoyama S, Tomoo K, Tsukamoto H, Shinohara Y, Iemitsu M, Nagano A, Isaka T, Hashimoto T. Ergogenic Effects of Very Low to Moderate Doses of Caffeine on Vertical Jump Performance. Int J Sport Nutr Exerc Metab. 2023 Jul 26;33(5):275-281. doi: 10.1123/ijsnem.2023-0061. Print 2023 Sep 1.

  PMID: 37414404 BACKGROUND

• Brook MS, Wilkinson DJ, Mitchell WK, Lund JN, Szewczyk NJ, Greenhaff PL, Smith K, Atherton PJ. Skeletal muscle hypertrophy adaptations predominate in the early stages of resistance exercise training, matching deuterium oxide-derived measures of muscle protein synthesis and mechanistic target of rapamycin complex 1 signaling. FASEB J. 2015 Nov;29(11):4485-96. doi: 10.1096/fj.15-273755. Epub 2015 Jul 13.

  PMID: 26169934 BACKGROUND

• Pickering C, Kiely J. Are low doses of caffeine as ergogenic as higher doses? A critical review highlighting the need for comparison with current best practice in caffeine research. Nutrition. 2019 Nov-Dec;67-68:110535. doi: 10.1016/j.nut.2019.06.016. Epub 2019 Jun 26.

  PMID: 31400738 BACKGROUND

• Grgic J, Trexler ET, Lazinica B, Pedisic Z. Effects of caffeine intake on muscle strength and power: a systematic review and meta-analysis. J Int Soc Sports Nutr. 2018 Mar 5;15:11. doi: 10.1186/s12970-018-0216-0. eCollection 2018.

  PMID: 29527137 BACKGROUND

• Guest NS, VanDusseldorp TA, Nelson MT, Grgic J, Schoenfeld BJ, Jenkins NDM, Arent SM, Antonio J, Stout JR, Trexler ET, Smith-Ryan AE, Goldstein ER, Kalman DS, Campbell BI. International society of sports nutrition position stand: caffeine and exercise performance. J Int Soc Sports Nutr. 2021 Jan 2;18(1):1. doi: 10.1186/s12970-020-00383-4.

  PMID: 33388079 BACKGROUND

• Grgic J, Grgic I, Pickering C, Schoenfeld BJ, Bishop DJ, Pedisic Z. Wake up and smell the coffee: caffeine supplementation and exercise performance-an umbrella review of 21 published meta-analyses. Br J Sports Med. 2020 Jun;54(11):681-688. doi: 10.1136/bjsports-2018-100278. Epub 2019 Mar 29.

  PMID: 30926628 BACKGROUND

MeSH Terms

Conditions

Muscular Atrophy; Hypertrophy

Interventions

Caffeine

Condition Hierarchy (Ancestors)

Neuromuscular Manifestations; Neurologic Manifestations; Nervous System Diseases; Atrophy; Pathological Conditions, Anatomical; Pathological Conditions, Signs and Symptoms; Signs and Symptoms

Intervention Hierarchy (Ancestors)

Xanthines; Alkaloids; Heterocyclic Compounds; Purinones; Purines; Heterocyclic Compounds, 2-Ring; Heterocyclic Compounds, Fused-Ring

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: TRIPLE
• Who Masked: PARTICIPANT, INVESTIGATOR, OUTCOMES ASSESSOR
• Masking Details: 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.
• Purpose: BASIC SCIENCE
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Assistant Professor

Model Details: This is a parallel-group, randomized, double-blind, placebo-controlled trial with four parallel supplementation strategies: (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. All participants undergo supervised resistance training three times per week.

Study Record Dates

• First Submitted: January 30, 2026
• First Posted: February 13, 2026
• Study Start: February 20, 2026
• Primary Completion: May 30, 2026
• Study Completion: June 7, 2026
• Last Updated: July 14, 2026

Record last verified: 2026-07

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL, SAP, ANALYTIC CODE
• Time Frame: Data requests will be accepted 6 months after the article is published; data will be accessible for 36 months.
• Access Criteria: Data sharing requests must be made by researchers with scientific justification and ethical approval. Requests will be evaluated, and those deemed appropriate will be signed with a confidentiality agreement and a data usage agreement. Requests will be received via abdullah.demirli@iuc.edu.tr e-mail address.

Locations

TU (1)