The Claim

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.

Source: Small muscle mass exercise enhances muscular adaptations? Effects of unilateral and bilateral biceps curl on maximum strength and muscle size changes.

What the research says

Supports is higher

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

Supports
61score
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.

Cause and effect
1 study reviewed
In plain English

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.

See the scientific wording

In untrained young women, 8 weeks of bilateral or unilateral biceps curl training results in no significant difference in muscle thickness gains of the elbow flexors at 60% or 70% of arm length, indicating similar hypertrophic responses regardless of exercise configuration.

What the research says

1 study

  1. Study: Small muscle mass exercise enhances muscular adaptations? Effects of unilateral and bilateral biceps curl on maximum strength and muscle size changes.

    Both ways of doing bicep curls—using both arms at once or one arm at a time—led to the same amount of muscle growth in the arms after 8 weeks, so neither way is better for building bigger biceps.

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

Fit Body Science verdict — we translate health claims into clear verdicts backed by peer-reviewed research.

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