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)2/3 vs 5.85±0.98 g/(ml)2/3, 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 (GCe) 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 GCe 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.
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