The Study
The effects of shoulder extension angle on elbow flexor hypertrophy in the cable curl exercise
This study is like a fair test where each person used one arm in one position and the other arm in a different position, randomly decided. It helps us see if changing shoulder angle affects arm muscle growth when everything else is kept the same. We can be fairly confident it doesn’t make a big difference — at least for beginners doing this specific exercise.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
We tested if doing curls with arms stretched back or in a normal position changes bicep growth.
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 560 / 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.
- 1The results show that changing shoulder angle doesn’t noticeably affect muscle growth when everything else is kept the same.
- 2Both arm positions led to about 7%–9% muscle growth.
- 3The difference between them was tiny and not meaningful.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Frontiers in Physiology
Year
2026
Authors
Stian Larsen, Benjamin Sandvik Kristiansen, Nordis Østerås Sandberg, Andrea Bao Fredriksen, Roland van den Tillaar, Milo Wolf, P. Swinton, Hallvard Nygaard Falch
Related Content
Claims (10)
When the total mechanical workload is the same, training muscles while they are stretched does not consistently lead to more muscle growth than training them while they are shortened.
If new guys do a specific arm curl workout for 10 weeks — going until their muscles are totally tired — their arm muscles get about 7% to 9% thicker, no matter how their shoulders are positioned, as long as the movement and resistance stay the same.
This idea says that a smarter math method can help scientists better tell when a workout doesn’t work — not just when they don’t have enough proof either way.
Doing more than a basic set of arm exercises and using more than one type of movement does not lead to noticeably greater muscle growth compared to a minimal routine.
Just because a study doesn’t find a clear difference in arm muscle growth between two curl types, it doesn’t mean there isn’t a real difference — the study might just be too small to catch it.
In men who are new to strength training, doing cable curls until muscle fatigue for 10 weeks leads to about the same increase in bicep muscle size whether the shoulder is kept straight back or pulled slightly backward, as long as the resistance and effort level are kept the same.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.