Marked adaptation of left ventricular (LV) structure in endurance athletes is well established. However, previous investigations of functional and mechanical adaptation have been contradictory. A lack of clarity in subjects' athletic performance level may have contributed to these disparate findings. This study aimed to describe structural, functional and mechanical characteristics of the cyclists' LV, based on clearly defined performance levels. Male elite cyclists (EC) (n=69), sub-elite cyclists (SEC) (n=30), and non-athletes (NA) (n=46), were comparatively studied using conventional and speckle tracking 2D echocardiography. Dilated eccentric hypertrophy was common in EC (34.7 %), but not SEC (3.3 %). Chamber concentricity was higher in EC compared to SEC (7.11±1.08 g/(ml) vs 5.85±0.98 g/(ml) , P<0.001). Ejection fraction (EF) was lower in EC compared to NA (57±5 % vs 59±4 %, P<0.05), and reduced EF was observed in a greater proportion of EC (11.6 %) compared to SEC (6.7 %). Global circumferential strain (GCε) was greater in EC (-18.4±2.4 %) and SEC (-19.8±2.7 %) compared to NA (-17.2±2.6 %) (P<0.05 and P<0.001). Early diastolic filling was lower in EC compared to SEC (0.72±0.14 cm/s vs 0.88±0.12 cm/s, P<0.001), as were septal E' (12±2 cm/s vs 15±2 cm/s, P<0.001) and lateral E' (18±4 cm/s vs 20±4 cm/s, P<0.05). The magnitude of LV structural adaptation was far greater in EC compared to SEC. Increased GCε may represent a compensatory mechanism to maintain stroke volume in the presence of increased chamber volume. Decreased E and E' velocities may be indicative of a considerable functional reserve in EC.2/3