- The effects of exercise training on cardiac structure and function have been thoroughly investigated in athletes from sport-developed nations; few data are available on sportsmen from sport-developing countries. To assess the incidence and magnitude of the "athlete heart" phenomenon in an elite group of Israeli cyclists. An echocardiography study was performed in 56 cyclists (49 males, mean age 38 +/- 10 years, weekly average training 13.1 +/- 5.9 hours); 96 sedentary subjects served as a control group. There were significant differences in left ventricular end-diastolic diameter (LVEDD) between cyclists and the control group (48 +/- 4.7 mm versus 45 +/- 4.1 mm respectively, P < 0.001), as well as in inter-ventricular septum (IVS) thickness (9.9 +/- 1.2 versus 8.9 +/- 1.2 mm, P < 0.001) and LV mass index (LVMI) (79 +/- 16 versus 68 +/- 13 g/m(2), P < 0.001). In 5% of the cyclists LVEDD exceeded the upper normal limit of 56 mm. In 7% of the cyclists IVS thickness exceeded the upper normal limit of 11 mm. LV hypertrophy defined as LVMI > or = 134 g/m(2) was absent in the entire cyclist group. Endurance sport activity in well-trained Israeli sportsmen results in a modest increment in LV dimensions and LV mass. LV dilatation and wall thickness above values compatible with primary cardiac disease are rare. These results highlight that in Israeli athletes any abnormal echocardiographic value must be thoroughly investigated and not simply assumed to be a consequence of sport activities.