The University of Granada participates in research linking a bacterium of the Roseburia genus with improved physical condition

This finding could lead to a probiotic for human consumption that helps maintain strength and fitness during aging

The study has been published in the prestigious scientific journal Gut

Scientists from the University of Almería and the University of Granada, together with researchers from Leiden University Medical Center (LUMC, Netherlands), have identified an intestinal bacterium of the genus Roseburia associated with stronger muscles and improved physical condition.

The results support the concept of an intestine-muscle axis. “Taken together, our findings provide solid evidence confirming the existence of an gut-muscle axis in which this identified bacterium positively modulates muscle metabolism and muscle strength,” says Jonatan Ruiz, professor in the Department of Physical Education and Sport at the UGR and researcher at the Joint University Institute for Sport and Health (iMUDS).

In addition, the scientists have observed that the bacterium is less abundant in older adults than in young adults, suggesting that its levels may decrease with age, a period in which muscle mass is lost.

“This opens up the possibility that the bacterium under investigation could be used as a probiotic to help preserve muscle strength during aging,” explains Borja Martínez Téllez, a researcher at the University of Almería.

Relationship between gut bacteria and muscle performance

The team analyzed whether certain gut microbes are associated with muscle strength and physical condition. To do this, they studied stool samples from 90 healthy young adults (18–25 years old) and 33 older adults (65 years old or older).

The participants in the experiments also performed several physical fitness tests, including handgrip strength, leg strength, and upper body strength (pectoral muscles), and their maximum oxygen consumption, an indicator of cardiorespiratory capacity, was measured.

Among the numerous bacterial groups detected, the genus Roseburia stands out, as its abundance is associated with increased muscle mass and strength. In particular, one species—Roseburia inulinivorans—shows a relationship with physical fitness.

Older adults in whom this bacterium is present have demonstrated 29% greater handgrip strength in experiments compared to those in whom the bacterium has not been detected. In young adults, greater abundance of this bacterium is associated with both greater handgrip strength and higher cardiorespiratory capacity.

Other species of the Roseburia genus offer different patterns: Roseburia intestinalis is related to leg and upper body strength in young adults, while Roseburia faecis and Roseburia hominis show no significant associations with the indicators studied.

Evaluating the gut-muscle connection

To explore whether Roseburia can directly influence muscle function, researchers have conducted experiments with mice. After temporarily reducing their gut microbiota with antibiotics, the animals were given human strains of the bacteria once a week for eight weeks.

The mice treated with the bacteria showed an approximate 30% increase in grip strength in their forelimbs compared to animals that did not receive it.

In addition, the mice developed larger muscle fibers and a higher proportion of type II muscle fibers, which are fast-twitch fibers, in the soleus muscle of the calf, which are important for strength and power. These changes were also accompanied by metabolic alterations in proteins and enzymes that are key to muscle energy production.

Limitations

The researchers point out several limitations. In experiments with mice, human strains of Roseburia did not permanently colonize the intestine, and the study did not directly evaluate certain biological mechanisms such as inflammatory pathways or neuromuscular signaling. Therefore, long-term research will be necessary to determine whether changes in R. inulinivorans levels cause improvements in muscle function or are a consequence of them.

The study was led by Ramón y Cajal researcher Borja Martínez-Téllez, from the Department of Nursing, Physiotherapy, and Medicine at the University of Almería, in collaboration with UGR professor Jonatan Ruiz and researcher Patrick CN Rensen (LUMC). Scientists from the University of Groningen (Netherlands) and other Spanish institutions in Valencia and Cádiz also participated in the work. The project was funded by the Martín Escudero Foundation, the Health Research Fund of the Carlos III Health Institute, and Leiden University Funds.

Bibliographic reference:

Martinez-Tellez B, Schönke M, Kovynev A, Garcia-Dominguez E, Ortiz-Alvarez L, Verhoeven A, Gacesa R, Vich Vila A, Ducarmon QR, Jimenez-Pavon D, Gomez-Cabrera MC, Weersma R, Smits WK, Giera M, Ruiz JR, Rensen PCN. Roseburia inulinivorans increases muscle strength. Gut. 2026. (IF = 26.2; Gastroenterology & Hepatology, D1). Doi: doi: 10.1136/gutjnl-2025-336980

Contacts:

Borja Martínez-Téllez
Department of Nursing, Physiotherapy, and Medicine
University of Almería, CIBEROBN
Email: @email
Phone: 950 21 41 15

Jonatan Ruiz Ruiz
Department of Physical Education and Sports Science
Faculty of Sports Sciences
University of Granada
Joint University Institute for Sport and Health (iMUDS), Ibs.Granada, CIBEROBN
Email: @email