How gut bacteria linked to muscle strength could help fight ageing

The trillions of microbes living in the human gut are increasingly recognised as important partners in human health. Scientists have linked the gut microbiome to several aspects of health, from metabolism and immunity to mental health .

A recent study suggests that these microbes may also influence an important aspect of fitness – muscle strength .

Muscle strength is a crucial feature of health for many reasons. It supports our joints and keeps our bones healthy, boosts athletic performance and even plays a role in metabolic health.

Muscle strength also helps us maintain independence later in life. As muscles gradually weaken as we get older, everyday tasks become harder and the risk of falls increases . Understanding what influences muscle strength is therefore an important part of healthy ageing research.

A recent study explored whether specific gut bacteria might be linked to muscle strength. Researchers analysed the gut microbiomes of two groups of adults: 90 young adults aged 18 to 25 and 33 older adults aged 65 to 75.

Participants provided stool samples so researchers could identify the microbes living in their gut. The researchers used DNA sequencing to read genetic material from the microbes in each sample. By comparing these sequences with large reference databases, they could determine which bacterial species were present and how abundant they were.

Participants also completed several tests designed to measure muscle strength, including a handgrip test. This involves squeezing a handheld device as hard as possible. Grip strength is widely used in health research because it provides a snapshot of overall muscle strength. Lower grip strength has also been linked to a higher risk of premature death.

When the researchers compared participants’ muscle strength with the microbes in their gut, one species stood out. Higher levels of a bacterium called Roseburia inulinivorans were linked to stronger performance across muscle strength measures.

Finding a link like this is interesting, but it does not necessarily mean the microbe is responsible. Many things can be associated without one directly causing the other. Ice-cream sales and shark attacks both increase during summer, for example – but eating ice cream does not cause shark attacks.

So to investigate whether the bacterium might actually influence muscle strength, the researchers carried out additional experiments in mice. After reducing the animals’ existing gut microbes, they introduced Roseburia inulinivorans into the mice’s digestive systems.

Mice that received the bacterium developed noticeably stronger grip strength in their arms than those that did not. Their muscle fibres also became larger and shifted toward a type of fibre associated with more powerful movements (called type II muscle fibres).

Further analysis suggested Roseburia inulinivorans may influence how muscles use energy. In mice given R inulinivorans, several energy‑related pathways inside muscle cells became more active.