The cardiovascular system is an energetically demanding network that relies on precise metabolic regulation to sustain continuous function. The heart primarily generates ATP through mitochondrial oxidative phosphorylation, utilizing substrates such as fatty acids, glucose, ketone bodies, and amino acids. Fatty acid oxidation (FAO) supplies 60-80% of myocardial energy under normal conditions, while glucose metabolism becomes crucial during stress or hypoxia. Ketone bodies offer an oxygen-efficient alternative, especially in heart failure, and amino acids contribute significantly under pathological states. Mitochondrial function is central to integrating these pathways, and its dysfunction leads to metabolic inefficiency and disease progression. Exercise plays a pivotal role in maintaining metabolic homeostasis, particularly during adolescence, a critical period of rapid growth and hormonal fluctuation. Physical activity enhances glucose uptake, improves lipid profiles, and induces beneficial hormonal changes, such as increased adiponectin and insulin sensitivity. Exercise also stimulates mitochondrial biogenesis, boosting oxidative capacity and resilience to metabolic stress. Acute exercise triggers immediate metabolic adaptations to meet energy demands, while chronic exercise induces long-term physiological changes, including increased mitochondrial density and improved hormonal regulation. These adaptations optimize energy metabolism, support homeostatic balance, and reduce the risk of metabolic disorders. Conversely, sedentary behavior, poor nutrition, stress, and circadian rhythm disruption can impair metabolic regulation and elevate disease risk. Regular exercise during adolescence not only confers direct physiological benefits but also fosters healthy lifestyle patterns, laying the foundation for lifelong metabolic and cardiovascular health.