Impact of an online-guided physical activity intervention on cognition, resting-state brain connectivity, and the gut microbiome in healthy older adults—a randomized controlled trial

Abstract Background Physical activity may enhance cognition in older adults, yet evidence from randomized controlled trials (RCTs) on mechanistic pathways remains inconclusive. Methods This single-blinded RCT examined the effects of an eight-week, online-guided, multicomponent physical activity intervention on cognitive functions, resting-state functional brain connectivity (rsFC), and the gut microbiome in 92 healthy older adults (46 per group). Participants were randomly assigned to a physical activity group performing moderate-to-vigorous-intensity aerobic exercises along with coordination and balance training, or to an active control group engaging in progressive muscle relaxation and listening to podcasts on aging-related topics. The primary outcome was the change in visual processing speed (in number of items/s) from pre- to post-assessment. Secondary outcomes included changes in further cognitive measures, rsFC, and diversity indices of the gut microbiome. Results The primary outcome showed no significant between-group differences. However, exploratory analyses revealed improvements in inhibition (η2 = .061; p = .025) and visual memory (η2 = .047; p = .040) in the physical activity group, which also showed increased rsFC between the visual and dorsal attention networks (η2 = .101; p = .009). Visual memory gains correlated with improvements in rsFC (p = .013). No between-group differences were observed in gut microbiome composition. Conclusions While visual processing speed remained unaffected, the findings suggest selective cognitive and associated brain connectivity benefits, particularly in memory and attention-related networks. The online format provided key advantages, such as minimizing social interaction as a potential confounder, ensuring broad accessibility, and enabling scalable implementation without specialized personnel. These results suggest that multicomponent physical training delivered online may support brain and cognitive health in older adults by targeting specific cognitive and neural mechanisms. Sources of funding: This project received funding from the European Union’s Horizon 2020 research and innovation program (Marie Skłodowska-Curie grant agreement no 859890)y. KF received funding from the German Research Foundation (DFG; FI 1424/2–2) and AR-R from the IZKF Advanced Medical Scientist Program of Jena University Hospital. CF and CG received funding from the Carl Zeiss Foundation IMPULS program (project number: P2019-01-006). Trial registration: The study was registered on the German Clinical Trials Register: https://drks.de/search/de/trial/DRKS00028022.