This 18-month study tracks how physical fitness relates to executive function in older adults, aiming to determine if fitness improvements predict better cognitive performance. Participants complete assessments at baseline and 18 months, including cardiorespiratory fitness (YMCA bike test), muscle strength (chest and leg press tests), and executive function (computer tasks with brain activity recording via EEG). Additional measures include physical activity questionnaires, cognitive screening (MMSE), memory tests (digit span), demographics (age, sex, education), and blood tests for APOE ε4 gene status. No exercise program will be provided, allowing observation of natural fitness-cognition relationships in daily life.