Marathon running demands significant cardiovascular and energy system management. Cardiologists advise pre-race screening, especially for those over 35 or with a family history of heart disease, to detect potential issues. Understanding 'cardiac drift,' where heart rate increases with body temperature, is crucial for managing exertion. Runners should monitor heart-rate zones and avoid intense training immediately after viral illnesses due to the risk of myocarditis. Proper fueling with carbohydrates and electrolytes is essential to prevent fatigue and maintain energy levels throughout the race.