One-arm curls make one arm stronger — but not both arms or bigger muscles
Small muscle mass exercise enhances muscular adaptations? Effects of unilateral and bilateral biceps curl on maximum strength and muscle size changes.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Unilateral training improved unilateral strength but didn’t improve bilateral strength.
Common belief: if you get stronger doing one-arm curls, you should be stronger doing two-arm curls. But the study found no difference in bilateral 1RM gains (Δ -0.28 kg, not significant).
Practical Takeaways
If you want to strengthen one arm (e.g., after injury or for sports like tennis), train it unilaterally—it gives a measurable 0.75 kg edge in single-arm strength.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Unilateral training improved unilateral strength but didn’t improve bilateral strength.
Common belief: if you get stronger doing one-arm curls, you should be stronger doing two-arm curls. But the study found no difference in bilateral 1RM gains (Δ -0.28 kg, not significant).
Practical Takeaways
If you want to strengthen one arm (e.g., after injury or for sports like tennis), train it unilaterally—it gives a measurable 0.75 kg edge in single-arm strength.
Publication
Journal
European journal of applied physiology
Year
2025
Authors
Witalo Kassiano, Ian Tricoli, Felipe Gomes, Vanessa Santos-Melo, Ingrid Manske, Gabriel Kunevaliki, Felipe Lisboa, Alexandre Miguel, Aline Prado, Natã Stavinski, Edilson S. Cyrino
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Claims (6)
Whether you lift weights with one arm or both at the same time, your biceps grow about the same amount after 8 weeks of training.
Doing bicep curls with one arm makes that arm stronger for one-arm curls, but doesn’t make you stronger for two-arm curls or the other arm.
Doing bicep curls one arm at a time makes your right arm stronger than doing them with both arms together, but doesn't make your biceps bigger than using both arms.
Training one arm at a time doesn’t make you stronger when lifting with both arms together — your total strength gain is the same as training both arms at once.
Training your right arm alone makes your right arm stronger, but doesn’t help your left arm get stronger — the benefit stays on the side you trained.