Test graduate-level understanding of physiological mechanisms (central and peripheral) by which high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) improve cardiovascular fitness in adults, and evaluate population health implications including comparative effectiveness (VO2max, endothelial function, autonomic modulation, mitochondrial adaptations), safety and risk profiles, adherence and sustainability, scalability and equity, and considerations for diverse adult subgroups and comorbidities; scope includes mechanisms, evidence synthesis, and translation to population-level recommendations.