The Claim

In untrained young men, performing cable biceps curls with matched resistance profiles for 10 weeks results in similar increases in biceps brachii muscle thickness across proximal, mid, and distal regions when training with the shoulder flexed at approximately 50° (Preacher curl) compared to training with the shoulder extended at approximately 50° (Bayesian curl), with relative hypertrophy ranging from 6% to 9% and moderate effect sizes (Hedges’ g: 0.49–0.73), indicating no meaningful advantage of longer muscle length positioning for regional biceps growth.

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

What the research says

Supports is higher

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

Supports
47score
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

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.

See the scientific wording

In untrained young men performing cable biceps curls with matched resistance profiles, training with the shoulder flexed at approximately 50° (Preacher curl) produces similar increases in biceps brachii muscle thickness across proximal, mid, and distal regions compared to training with the shoulder extended at approximately 50° (Bayesian curl), with relative hypertrophy ranging from 6% to 9% and moderate effect sizes (Hedges’ g: 0.49–0.73), indicating no meaningful advantage of longer muscle length positioning for regional biceps growth over 10 weeks.

What the research says

1 study

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

    The study found that both types of bicep curls—done with the arm positioned forward or backward—led to similar muscle growth, so neither has a clear edge.

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

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Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.