Optimizing Combined Physical and Cognitive Activity in Community-Dwelling Older Adults.

This laboratory-based interventional study aims to determine which combination of physical activity intensity and cognitive activity difficulty yields the greatest acute cognitive benefits in community-dwelling older adults. The main question it aims to answer is: \- Which combination of physical and cognitive activity results in the greatest short-term improvement in cognitive functioning? Researchers will compare four different combinations of physical intensity and cognitive task difficulty to determine whether one combination stands out. In addition, the study examines whether these effects differ depending on baseline cardiorespiratory fitness. Participants will: * undergo a preparatory phase in which their cardiorespiratory fitness, individualized physical activity intensity levels, and cognitive activity difficulty levels are established * visit the laboratory four times, with one week between visits, to complete each combination of physical and cognitive activity (light vs. moderate physical activity × easy vs. challenging cognitive activity) * complete cognitive tests immediately before and after each condition

Inclusion Criteria: * Aged 65 years or older * Community-dwelling * Able to safely walk on a treadmill and complete the 6-Minute Walk Test * Sufficient Dutch proficiency to understand study instructions and complete study procedures Exclusion Criteria: * MoCA score \< 23 * Severe cognitive or physical impairment that would hinder participation or understanding of study procedures * Use of medication affecting heart rate * Any medical condition contraindicating engagement in physical or cognitive activity * Severe visual or hearing impairment that would prevent valid participation in the study procedures