The Study
Acute and chronic regional changes in elbow flexor thickness after resistance training with dumbbell curl or dumbbell row exercises
This study watched how two different arm exercises changed the size of muscles in people's arms. It found that one exercise (curls) seemed to make the muscle bigger in some spots than the other (rows), but it didn't prove that curls caused the change — maybe the people just tried harder during curls.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
This study tested whether doing curls or rows with dumbbells makes your biceps bigger over time.
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 545 / 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 — if you want your whole biceps to grow, curls are better than rows, especially for the lower part near the elbow.
- 2After 8 weeks, curls made the top part of the biceps 5% thicker and the bottom part 11% thicker.
- 3Rows only made the top part 5% thicker — the bottom barely changed (1%).
- 4Right after one workout, curls made the top swell 19%, rows only 13%.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Sport Sciences for Health
Year
2025
Authors
B. F. Leitão, J. Albarello, G. H. Halmenschlager, P. Mannarino, J. P. Nunes, B. D. de Salles, Thiago T. Matta
Related Content
Claims (9)
When muscle thickness is measured using ultrasound after strength training, differences in thickness between the upper and lower parts of the biceps indicate localized muscle growth, not just temporary fluid buildup.
When you do bicep curls (an isolation exercise), your muscles get a bigger 'pump' right after compared to doing rows (a compound exercise), especially near the top of your arm close to your shoulder.
After 8 weeks of training, dumbbell curls lead to a small increase in muscle thickness near the elbow in the biceps area, while dumbbell rows do not produce a similar change in the distal regions, suggesting different exercises may affect muscle growth in different locations.
After 8 weeks of doing dumbbell rows, the muscles at the back of the upper arm near the elbow show almost no growth, suggesting that this exercise may not effectively build muscle in those specific areas.
After one workout session, dumbbell curls cause more temporary swelling in the upper arm muscles than dumbbell rows, suggesting that the two exercises may trigger different levels of metabolic stress or fluid buildup in those muscles.
After one workout, dumbbell curls cause a larger temporary increase in muscle thickness near the elbow compared to dumbbell rows, which may reflect differences in how much the muscles are activated or how much metabolic stress they experience during each exercise.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.