Physical activity is undeniably associated with numerous health benefits. However, performance of high intensity and/or high-volume exercise poses a significant physiological challenge to the cardiovascular and respiratory systems, which must undergo several adaptations to meet the increased metabolic demands of the organism. Repeated and prolonged exposure to training leads to long-term cardiac remodeling aimed at optimizing the efficiency of the work performed by the heart during exertion. This article discusses some of the fundamental mechanisms of cardiovascular physiology during exercise including adaptive responses to acute bouts of exercise and longer term structural and functional characteristics of the athlete's heart.