AMPLIFI: Adaptive Modulation of Plasticity Through Lactate and Fitness Interventions

The AMPLIFI study (Adaptive Modulation of Plasticity through Lactate and Fitness Interventions) investigates how short-term aerobic exercise influences brain plasticity and learning in older adults and stroke survivors. The study compares three groups: one performing aerobic cycling at an intensity that elevates lactate levels, one performing low-intensity exercise, and one receiving health education without exercise. All participants will complete motor learning tasks and undergo brain-stimulation testing using transcranial magnetic stimulation (TMS) to assess how well the brain responds to training. The goal is to understand whether different types of exercise can improve brain function, movement, and memory, and how the body's response to exercise (like lactate levels) might support brain health. This research may help identify low-cost, non-invasive interventions-such as targeted exercise-that improve motor and cognitive outcomes in aging and stroke recovery.

Inclusion Criteria: For All Participants: * Able to provide informed consent * Right-handed (for TMS consistency) * English-speaking * Clearance for moderate-intensity aerobic exercise * Able to safely sit and pedal a stationary cycle ergometer * No contraindications to TMS (e.g., no metal in skull, pacemakers, or seizure history) Younger Adults (18-35): * No history of neurological or psychiatric conditions * Not currently on medications that affect the central nervous system Older Adults (60-85): * No diagnosis of dementia * Independent in activities of daily living * No stroke history Stroke Survivors (40-85): * At least 6 months post-stroke (chronic phase) * Medically stable and cleared for aerobic exercise * Able to engage in motor learning task (with or without hemiparetic adaptations) Exclusion Criteria: * History of epilepsy or seizures * Current substance abuse or uncontrolled psychiatric disorder * Severe cardiovascular disease or unstable medical condition * Pregnancy * Contraindications to TMS or exercise testing (e.g., implanted neurostimulators, severe hypertension) * Participation in another interventional trial within the past 30 days