The Claim

Untrained men who perform unilateral cable curls to momentary failure for 10 weeks, completing 6–8 sets per week, will 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.

Source: The effects of shoulder extension angle on elbow flexor hypertrophy in the cable curl exercise

What the research says

Supports is higher

Support is ahead, but a single strong opposing study can change this.

Supports
60score
Challenges
0score

These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.

Quantitative
1 study reviewed
In plain English

If new gym guys do a specific arm curl workout for 10 weeks — going until their muscles are totally tired — their biceps 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 weekly sets 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.

Why this might work

When the biceps are worked hard until they can't do another rep, the muscle fibers stretch and pull against resistance, which sends signals inside the cells to build more muscle proteins. Over time, this makes the muscle fibers thicker, and since the exercise is done the same way every time with full movement and consistent resistance, the thickening happens evenly along the whole muscle.

Supported mechanismbased on 1 study

What the research says

1 study

  1. Study: The effects of shoulder extension angle on elbow flexor hypertrophy in the cable curl exercise

    New guys who did this specific arm curl workout for 10 weeks got their biceps about 7–9% thicker, no matter how they held their shoulders—as long as they curled all the way and pushed until tired. The study proved shoulder position didn’t matter.

Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies

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