CHARGE: Pilot Trial of Self-directed Use of Resources for Physical Activity

Inclusion Criteria: * Age 18-75 * Reports a desire to increase physical activity level * Not meeting minimum aerobic PA as indicated by L-CAT endorsement indicating level of activity below moderate (moderate defined as \>= 5x/week activity or higher) * Reports willingness to use LLMs to help with exercise goals. * Access to internet through phone data plan or home Wi-Fi. Exclusion Criteria: * Conditions warranting more extensive supervision of physical activity, including: * Any history of MI or stroke, arrhythmias, or heart failure * Uncontrolled hypertension * Type 1 or 2 diabetes * COPD or asthma * Recent orthopedic surgery or fracture * Advanced Parkinson's * Pregnant or planning to become pregnant in next 9 months * Active cancer undergoing treatment * Recent major surgery (\<12 weeks) * Use of assistive devices for ambulation * History of eating disorder diagnosis * Dementia diagnosis * Unable to read on own. * Hospitalization for mental health reasons in past year * Has used LLM to support physical activity goals in prior 3 months. * Currently enrolled in a structured program to promote physical activity or weight loss.