Analysis Version
v1
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Back to Study: Small muscle mass exercise enhances muscular adapt...
causal
Analysis v1
61
Pro
0
Against

Training your right arm alone makes your right arm stronger, but doesn’t help your left arm get stronger — the benefit stays on the side you trained.

Scientific Claim

In untrained young women, unilateral biceps curl training improves unilateral strength in the trained right arm but not the left arm, suggesting asymmetrical neural adaptations that do not generalize across limbs.

Original Statement

“U-BC exhibited greater changes in 1RM UNI right arm [∆ 0.75 (0.22, 1.27) kg], but no between-group difference was observed in 1RM UNI left arm [∆ 0.43 (-0.24, 0.93) kg].”

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

Evidence Quality Assessment

Claim Status

appropriately stated

Study Design Support

Design supports claim

Appropriate Language Strength

definitive

Can make definitive causal claims

Assessment Explanation

The RCT design and precise measurement of left vs. right arm strength changes allow definitive conclusions about limb-specific adaptation. The confidence intervals clearly distinguish the right arm effect from the null left arm effect.

Evidence from Studies

Supporting (1)

61
61

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

Randomized Controlled Trial
Human
2025 Dec 8

When young women trained only one arm with dumbbells, that arm got stronger, but the other arm didn’t—meaning the brain learned to use the trained arm better, but didn’t pass that skill to the other arm.

Contradicting (0)

0
No contradicting evidence found

Source Study

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

Score: 61
DOI: 10.1007/s00421-025-06033-4

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