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.

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Evidence from Studies

Supporting (1)

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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.

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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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