The Claim
Untrained men who perform unilateral cable curls to momentary failure for 10 weeks, completing 6–8 sets per week, experience approximately 7%–9% increases in elbow flexor muscle thickness at both proximal and distal measurement sites, irrespective of shoulder extension angle, provided that resistance profiles and elbow range of motion are standardized.
What the research says
Supports is higher
Support is ahead, but a single strong opposing study can change this.
These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.
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.
See the scientific wording
Untrained men performing unilateral cable curls to momentary failure for 10 weeks with 6–8 sets per week experience approximately 7%–9% increases in elbow flexor muscle thickness at both proximal and distal sites, regardless of shoulder extension angle, when resistance profiles and elbow range of motion are standardized.
When the biceps muscle is stretched and pulled hard during curls until it can't move anymore, the force on the muscle fibers triggers chemical signals that tell the cells to build more muscle proteins. Over time, this causes the muscle fibers to get thicker, making the whole muscle bigger — no matter how the shoulder is positioned, as long as the same amount of force is applied to the muscle.
What the research says
1 studyStudy: The effects of shoulder extension angle on elbow flexor hypertrophy in the cable curl exercise
New guys who did arm curls until they couldn't do more, for 10 weeks, got their biceps about 7–9% thicker — no matter if their shoulders were bent back or straight, as long as they did the same curls the same way.
Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.