The Claim

Myofibrillar hypertrophy, characterized by the increase in size and number of contractile proteins actin and myosin, is the primary functional mechanism underlying muscle growth, whereas sarcoplasmic expansion occurs secondarily and in proportion to myofibrillar changes without independent regulatory control.

Source: Cut out the BS. Do THIS to build muscle [3 New Studies]

What the research says

Challenges is higher

Challenge is ahead, but a single strong supporting study can change this.

Supports
1score
Challenges
39score

These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.

How it works
2 studies reviewed
In plain English

Muscle growth mainly happens because the tiny fibers that make your muscles contract get bigger and stronger; the fluid part of the muscle increases too, but only as a side effect and not on its own.

See the scientific wording

Myofibrillar hypertrophy—the increase in size and number of contractile proteins (actin and myosin)—is the primary functional component of muscle growth, while sarcoplasmic expansion occurs secondarily and proportionally without independent regulation.

What the research says

2 studies

  1. Study: Muscle fiber hypertrophy in response to 6 weeks of high-volume resistance training in trained young men is largely attributed to sarcoplasmic hypertrophy

    The study found that muscles grew bigger not because of more contractile proteins like actin and myosin, but because of an increase in fluid and energy-related proteins inside the muscle cells.

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Read analysis

Score breakdown, mechanism chain, raw evidence, ideal studies needed & 2 supporting studies

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

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