Middle age is a critical time for cognitive changes that may precede dementia onset. Interestingly, studies have shown that lifestyle factors such as exercise can reverse age-related cognitive decline and improve memory function. However, the underlying mechanisms that underpin these effects are unknown. Besides a decline in physical fitness, middle age is characterized by extensive change in gastrointestinal function, gut microbiota composition, and related metabolites. The microbiota-gut-brain axis has been linked to age-associated changes, including cognitive ageing and memory performance. Notably, it has been demonstrated that exercise can modify gut microbiota composition and gastrointestinal health. To elucidate the mechanism between exercise, gut microbiota and cognition, we transplanted faecal microbiota (FMT) from human middle-aged participants undergoing physical exercise into sedentary rats.