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Claim
Strong Support
quantitative
Analysis v3

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...

60
Pro
0
Against

Mechanism

Synthesis from 1 study

How it works

When you lift a weight until your arm can't move anymore, the force on your biceps tells the muscle cells to make more building blocks for muscle. Do this enough times over weeks, and the muscle gets thicker all along its length — whether your shoulder is bent or straight — as long as you're...

Most probable mechanism

In Simple Terms

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.

Causal chain
1

Muscle fibers experience high mechanical tension during concentric and eccentric contractions under load to momentary failure, activating mechanosensitive ion channels and integrin-based signaling complexes.

Verified by multiple studies
which leads to
2

Mechanical tension triggers intracellular signaling cascades involving mTORC1, MAPK, and other pathways that increase the rate of muscle protein synthesis.

Supported by evidence
which leads to
3

Sustained elevation in protein synthesis over multiple training sessions leads to net accretion of contractile proteins within muscle fibers, increasing cross-sectional area.

Verified by multiple studies
which leads to
4

Hypertrophy occurs uniformly along the length of the muscle due to consistent mechanical loading across the full range of motion and standardized resistance profile.

Verified by multiple studies

Evidence from Studies

Supporting (1)

60

Community contributions welcome

60

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

Randomized Controlled Trial
Human
2026

Contradicting (0)

0

Community contributions welcome

No contradicting evidence found

Gold Standard Evidence Needed

According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.

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Source Study

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

Score: 60
DOI: 10.3389/fphys.2026.1750722

Merged Assertions

1

The following assertions have been merged into this one because they express the same claim:

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.

NaN% similar

Similar Assertions

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.

60
0
90%

If you're new to lifting, changing your arm position during cable curls doesn't make one part of your biceps grow more than another — both positions give you the same kind of muscle growth over 10 weeks if everything else is kept equal.

60
0
87%

In untrained men performing cable curls with the same resistance, movement range, and effort, changing the shoulder angle between neutral and fully extended positions leads to similar increases in elbow muscle thickness after 10 weeks of training.

60
0
86%

If you're new to lifting and do cable curls the same way each time, it doesn't really matter whether your arms are stretched far back or in a neutral position — your biceps will grow about the same amount after 10 weeks.

60
0
85%

Doing bicep curls with your arm in front of your body or behind your body gives you the same muscle growth and strength gains if you're using the same amount of weight and doing the same number of reps.

54
0
84%