The Study
Six weeks of caffeine supplementation enhances muscle thickness without augmenting strength gains—a randomized controlled trial
This study gave some guys caffeine before their workouts and found their arms got a little bigger — but not stronger. It’s like testing if eating a special snack makes your muscles grow faster, but we don’t know if the guys knew they were getting the snack or not, so we can’t be totally sure it was the caffeine that did it.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
People who drank caffeine before lifting weights for six weeks saw their biceps and triceps get thicker, but they didn’t lift heavier weights or change their overall body shape.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 554 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes — muscles grew in specific areas without improving performance or overall physique, suggesting caffeine might help muscles grow in a way that doesn’t show up on scales or strength tests.
- 2Caffeine group: biceps grew more (p=0.009), triceps grew more (p=0.049).
- 3No difference in strength, endurance, or body fat/lean mass.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Sport Sciences for Health
Year
2026
Authors
Ahmadreza Eshaghian, M. G. Moghaddam, M. Fathi
Related Content
Claims (7)
Caffeine makes people feel like they are working harder during exercise and increases their motivation to work out, but it does not cause muscles to grow unless the physical load on the muscles is increased.
Drinking caffeine in the morning increases core body temperature and enhances physical performance. Regular caffeine use over time does not affect muscle growth because the body adapts to its presence.
Taking caffeine before resistance training does not increase strength or change body composition in recreationally active men after six weeks, but it does increase muscle thickness in the trained areas.
In recreationally active men, taking caffeine while doing resistance training for six weeks does not change total fat mass or lean mass, even though muscle thickness increases.
Taking caffeine supplements for six weeks while doing resistance training does not increase maximum strength in the bench press or bench pull, and does not improve the ability to perform repeated lifts at 60% of maximum capacity in recreationally active men.
In recreationally active men, taking 3 mg of caffeine per kilogram of body weight one hour before three weekly upper-body weightlifting sessions for six weeks results in greater increases in biceps and triceps muscle thickness compared to taking a placebo.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.