Researchers from the University of Granada, the University of Almería and the Leiden University Medical Center have discovered a bacterium of the genus Roseburia that is associated with increased muscle strength and better physical performance. In particular, the species Roseburia inulinivorans showed a positive association with muscle mass and strength in the study. The results were published in the journal “Gut” on March 12, 2026.

The team analysed stool samples from 90 healthy young adults (18–25 years) and 33 older people (65 years and older). The participants completed strength and endurance tests, including hand grip strength, leg strength, upper body strength and maximum oxygen uptake. Among the numerous intestinal bacteria detected, the genus Roseburia stood out: its higher abundance was accompanied by increased muscle strength. Older people in whom Roseburia inulinivorans was detectable had on average 29 percent higher grip strength than those without this germ. In young grownups, the amount of bacteria additionally correlated with better cardiorespiratory fitness.

To test for a direct influence, mice were given human Roseburia strains for eight weeks after temporary intestinal germ reduction. The treated animals showed about 30 percent higher gripping strength in the front paws, larger muscle fibers and a higher proportion of fast-twitch type II fibers in the calf muscle, as well as favorable changes in muscle metabolism.

The researchers see this as evidence of an gut-muscle axis: Roseburia inulinivorans could have a positive effect on muscle metabolism. Since the bacteria are less common in older people, a decline could be related to age-related muscle loss. The results open up the prospect of using the bacterium as a probiotic to maintain muscle strength and fitness in old age.

The study highlights that the gut microbiome could play a role in physical performance. In the long term, further studies are needed to clarify causal relationships and validate possible therapeutic approaches.

Original Paper:

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. Good. 2026. (IF = 26.2; Gastroenterology & Hepatology, D1). doi: doi: 10.1136/gutjnl-2025-336980

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