The Claim

Resistance training causes a decrease in type IIX muscle fibers and an increase in type IIAX hybrid fibers across all training protocols in previously untrained women over 6 weeks, regardless of training speed or intensity.

Source: Early-phase muscular adaptations in response to slow-speed versus traditional resistance-training regimens

What the research says

Supports is higher

Support is ahead, but a single strong opposing study can change this.

Supports
41score
Challenges
0score

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

Cause and effect
1 study reviewed
In plain English

When women who haven't trained before do weightlifting for 6 weeks, their fast-twitch muscle fibers change: some decrease while others increase, and this happens no matter how fast or hard they train.

See the scientific wording

Resistance training causes a decrease in type IIX muscle fibers and an increase in type IIAX hybrid fibers across all training protocols in previously untrained women over 6 weeks, regardless of training speed or intensity.

What the research says

1 study

  1. Study: Early-phase muscular adaptations in response to slow-speed versus traditional resistance-training regimens

    The study looked at women doing different types of weight training and found that all of them reduced one type of muscle fiber and increased another, just like the claim said, even though some methods worked a bit better than others.

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.