It is not that simple.

They have found first a correlation between the presence of this species of bacteria and muscle strength in humans.

Then they have made an attempt to determine whether this correlation reflects a causal relationship.

So they have fed mice previously treated with antibiotics, to remove their own gut bacteria, with this kind of bacteria extracted from humans.

They have indeed seen an increase in muscular strength at the mice that have received the human bacteria, which seems to confirm causality between the presence of this bacterium and muscle strength.

While they have also determined the biochemical changes in muscles that have caused increased strength, the mechanism of how the bacteria have influenced that remains a mystery. Perhaps this bacterium produces some substance that mimics a human hormone, e.g. a steroid.

Paywalled research article: https://gut.bmj.com/content/early/2026/03/03/gutjnl-2025-336...