Introduction: Speckle tracking echocardiographic analysis of myocardial strain vectors allows in-depth analysis of subtle modifi cations of global and regional myocardial mechanics that precede global myocardial function changes. The aim of this study was to evaluate functional correlates of physiological myocardial hypertrophy in young athletes using both standard Doppler echocardiographic and peak myocardial systolic strain. Methods: We studied with a GE Vivid S5 system 37 young athletes (athletes: A; endurance activity: EA, n = 30; strength activity: SA, n = 7) with 5.3 ± 3.8 y. train ing experience and 13.9 ± 5 hours/week training load, compared to 22 controls (C). We measured conventional 2D systolic and pulsed Doppler flow and tissue annular indices of left ventricle (LV) systolic and diastolic function, and global LV peak systolic longitudinal (GLSS%; apical views), and maximum radial (GRMS %), and circumferential strain (GCMS, short axis views), and right ventricular (RV) lateral wall peak systolic longitudinal strain (PLSS%, 4-chamber). Atrial compliance was calculated as (maximum volume – minimum/minimum x 100). Results: Blood pressure, age, BSA and estimated pulmonary systolic pressure were similar in athletes and C, LV end-diastolic hypertrophy index (0.36 ± 0.1 vs 0.33 ± 0.1, p <0.05) and RV mean wall thickness (mean: 5.2 ± 1 vs 4.2 ± 1 mm, p < 0.01) were increased in athletes. Increased LV wall thickness was associated with normal LV and LA anatomy and function indices, unchanged GRMS and GCMS, and reduced GLSS in both EA and SA (C: -21.5 ± 1.9%, EA: -20.3 ± 1.8%, SA: -19.1 ± 2%, p < 0.01), whereas increased RV wall thickness was associated with reduced mid-lateral wall PLSS (-30 ± 4% vs -32 ± 4, p < 0.05) and secondary increase in atrial volumes with reduced atrial compliance (107 ± 37% vs 139 ± 63%, p < 0.05), without differences between EA and SA. Conclusions: Young athletes show a mild biventricular increase in wall thickness, independent of type of exertion, which leads to more extensive functional changes in the right than in the left heart. The longitudinal component of strain is more sensitive than the circumferential or the radial in detecting these mild functional changes in response to physiologic hypertrophy.