The Claim

In untrained young men, type II muscle fibers exhibit greater myofibril density than type I fibers at baseline, and resistance training maintains this difference while increasing overall fiber size.

Source: Myofibril and Mitochondrial Area Changes in Type I and II Fibers Following 10 Weeks of Resistance Training in Previously Untrained Men

What the research says

Challenges is higher

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

Supports
0score
Challenges
31score

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

Description
1 study reviewed
In plain English

In young men who don't exercise, fast-twitch muscle fibers are more tightly packed with muscle-building parts than slow-twitch fibers. When they start lifting weights, this difference stays the same, but all muscle fibers get bigger.

See the scientific wording

Type II muscle fibers in untrained young men show greater myofibril density than type I fibers at baseline, with resistance training maintaining this difference while increasing overall fiber size.

What the research says

1 study

  1. Study: Myofibril and Mitochondrial Area Changes in Type I and II Fibers Following 10 Weeks of Resistance Training in Previously Untrained Men

    The study looked at resistance training in untrained men and found that myofibril density didn't change in either fiber type, which goes against the claim that type II fibers have higher density and keep it after training.

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.

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