Back to Bigger Biceps: This NEW Study Is Interesting
Claim
Strong Support
quantitative
Analysis v3

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.

60
Pro
0
Against

Mechanism

Synthesis from 3 studies

How it works

Moving your arm differently during a curl changes how stretched and squeezed your biceps muscle gets, which might make tiny differences in muscle growth. But these differences are so small that you’d need a lot of people and a long time to notice them — so just because a study didn’t find a...

Most probable mechanism

In Simple Terms

When you move your arm in different positions during a curl, the way your biceps muscle stretches and tightens changes slightly. This changes how much force each part of the muscle feels and how much energy it uses, which can lead to small differences in how much the muscle grows over time — even if those differences are too small to easily measure in short studies with few people.

Causal chain
1

Shoulder position alters the length-tension relationship of the biceps brachii, changing the degree of sarcomere strain across muscle fibers during elbow flexion.

Indirect evidence only
which leads to
2

Altered sarcomere strain modifies the distribution of mechanical tension within the muscle, leading to regional differences in fiber recruitment and force production.

Indirect evidence only
which leads to
3

Changes in tension distribution influence local metabolic demand, including calcium flux, lactate accumulation, and hypoxia, which modulate signaling pathways linked to protein synthesis.

Not yet directly tested
which leads to
4

These subtle variations in mechanical and metabolic stimuli may produce small differences in myofibrillar protein accretion over time, detectable only with large sample sizes or long durations.

Indirect evidence only

Evidence from Studies

Supporting (3)

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
54

Comparison Between Shoulder Flexed and Extended Positions in Elbow Flexion Resistance Training on Regional Hypertrophy and Maximum Strength: Preacher versus Bayesian Cable Curls

Randomized Controlled Trial
Human
2025 Apr
47

Comparison Between Shoulder Flexed and Extended Positions in Elbow Flexion Resistance Training on Regional Hypertrophy and Maximum Strength: Preacher versus Bayesian Cable Curls

Randomized Controlled Trial
Human
2025 Apr

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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Similar Assertions

Different ways of performing biceps curls lead to small but detectable differences in how much muscle grows in specific areas and how much strength improves for that movement.

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If you're a guy new to lifting, doing bicep curls with your arms in front of you or behind you doesn’t really make a difference in how much your biceps grow — both ways work about the same.

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In untrained young women, doing biceps curls with both arms at the same time or one arm at a time leads to the same amount of muscle growth in the upper arm after 8 weeks, suggesting that how much total muscle is activated during the exercise does not control how much the muscle grows.

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For guys new to lifting, doing bicep curls with your arms in front of your body works just as well for building arm muscle as doing them with your arms behind you — both give about the same 6% to 9% growth in 10 weeks.

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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.

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