The study investigated the effect of 24 weeks of elastic band training on gut microbiota and physical function in older adults with possible sarcopenia. The resistance training group showed improved physical function and lower levels of the inflammatory marker TNF-α. The training led to changes in the composition of the intestinal microflora, specifically to a decrease in Eisenbergiella and Eggerthella bacteria and an increase in the genus Bacillus. The training group showed higher plasma concentrations of short-chain fatty acids—acetate and propionate—that are important for health. Changes in propionate levels were positively correlated with performance in tests of physical function and muscle mass. The results suggest that resistance training with elastic bands may help prevent and treat sarcopenia by modulating gut microbiota and the production of health-promoting metabolites.