Athlete's heart is associated with left ventricular hypertrophy and supranormal cardiac function, suggesting that this is a physiological phenomenon. Hypertrophy alone cannot explain increase in cardiac function, therefore, other mechanisms, such as better atrio-arterial function, might be involved. Our study uses new and complex methods, such as 4D echo and 2D speckle tracking echo (STE), to evaluate complex changes of left atrial (LA) and left ventricular (LV) structure and function in order to test atrio-ventriculo-arterial coupling and its benefits on cardiac function. Methods: 100 subjects (22±8 years, 74 male) were enrolled: 70 endurance athletes and a control group of 30 sex- and age- matched normal subjects. Conventional and 4D auto LV quantification echo was used to assess LV and LA geometry, EF, and LV systolic deformation: radial strain (rS), longitudinal strain (LS), and circumferential strain (CS). STE was used to measure LA deformation: contraction from peak negative strain (PNS); relaxation from peak positive strain (PPS), and global strain (GS). Arterial function was assessed from augmentation index (Aix), β index, and carotido-femoral pulse wave velocity (PWV); and ventriculo-arterial coupling from amplitude of the compression wave (CW) from the carotid wave-intensity tracings. Results: Although athletes had LVH and larger LA volume (105±28 vs. 85±32 g/m2, and 48±10 vs. 41±6 ml, both p<0.05), they showed supranormal LV and LA deformation, whereas EF was similar with controls. They also had better arterial function, with improved ventriculo-arterial coupling (table). Univariate analysis showed that LS was directly related to GS (r=0.50, r2=0.31), and to CW (r=0.44, r2=0.31); and inversely related to AIx (r=-0.62, r2=0.36) and to PWV (r=-0.72, r2=0.41) (all p<0.05). View this table: Table 1. Atrio-ventriculo-arterial coupling Conclusion: Athlete's heart is a pure physiological adaptive phenomenon, associated with supranormal LV and LA deformation, due to better arterial function, with optimized atrio-ventriculo-arterial coupling.