When muscles get bigger over time, it’s not because the non-working parts inside them swell up—it’s because the actual muscle fibers that do the work grow more, and that’s what really matters.

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Evidence from Studies

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Load-induced human skeletal muscle hypertrophy: Mechanisms, myths, and misconceptions

Narrative Review

2025 Nov 21

This study says that muscles grow bigger mainly because the actual muscle fibers get thicker, not because of extra fluid or non-muscle stuff inside — so the idea that 'pump' or water swelling makes muscles grow long-term is mostly a myth.

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No contradicting evidence found

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Source Study

Load-induced human skeletal muscle hypertrophy: Mechanisms, myths, and misconceptions

Score: 1

DOI: 10.1016/j.jshs.2025.101104

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