Performance of the cardiovascular system is one of the primary determinants of exercise potential. Coordinated biventricular function with the ability to augment of cardiac output underlies the ability to obtain normal and supra-normal levels of peak exercise capacity. This chapter will provide an overview of cardiac structure and function as it relates to exercise capacity. Specifically, characteristics of both the left and right ventricle will discussed with emphasis on their differential structure and function during physical activity. Mechanisms of contraction, relaxation, and chronotropic function during exercise and at rest in sedentary individuals and in trained athlete will be reviewed. Next, we will address the established findings and the areas of uncertainty regarding how the heart responds to exercise training and deconditioning. Focus topics will include structural change, functional adaptation, and underlying cellular modifications. Finally, a brief discussion about the impact and causality of intrinsic structural heart disease on exercise capacity limitations will be provided.