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Introduction
The cardiovascular (CV) benefits of regular physical exercise are well documented. Cardiorespiratory fitness is a strong predictor of CV disease and all-cause mortality, 1 2 with increases in cardiorespiratory fitness associated with corresponding decreases in CV disease risk. 3 Indeed, a 41% reduction in mortality was reported in 786 former Tour de France cyclists compared with the general French male population. 4 The effects of exercise upon the myocardium and vascular system are dependent upon the frequency, intensity and duration of the exercise itself. Following a prolonged period (>=6 months) of regular intensive exercise in previously untrained individuals, resting and submaximal exercising heart rates are typically 5-20 beats lower, with an increase in stroke volume of ~20% and enhanced myocardial contractility. 5 Structurally, all four heart chambers increase in volume with mild increases in wall thicknesses, resulting in greater cardiac mass due to increased myocardial cell size.
With this in mind, the present paper aims to review the basic science behind the CV benefits of exercise. Attention will be paid to understanding (1) the relationship between exercise and cardiac remodelling; (2) the cardiac cellular and molecular adaptations in response to exercise, including the examination of molecular mechanisms of physiological cardiac growth and applying these mechanisms to identify new therapeutic targets to prevent or reverse pathological remodelling and heart failure; and (3) vascular adaptations in response to exercise. Finally, this review will briefly examine how to optimise the CV benefits of exercise by considering how much and how intense exercise should be.
Cardiac structure and functional adaptations in response to exercise
Exercise and cardiac remodelling
The term 'athlete's heart' refers to a constellation of adaptations that affect the structure, electrical conduction and function of the heart that facilitate appropriate increases in cardiac output during exercise. There is a plethora of studies demonstrating dilatation of all four cardiac chambers and an increase in the maximal wall thickness in trained individuals compared with sedentary controls. While CV adaptation depends on the modality, intensity and volume of conditioning, even in previously sedentary individuals, intensive and prolonged endurance training leads to cardiac remodelling mimicking parameters commonly observed in athletes. 6
Athlete's heart dogma suggests that endurance athletes present with eccentric hypertrophy, while athletes whose training is predominately resistance based...