Recent studies showed contrasting findings in morphological changes due to competitive soccer in adolescent players (SP). We present a prospective study in 315 consecutive adolescent (10-14 years) male elite SP and 53 healthy matched active controls (CON). All participants underwent a complete transthoracic two-dimensional echocardiography (TTE). The mean age in SP was 12.8 +/- 0.65 years compared to 12.6 +/- 0.8 years in CON. For all left ventricular (LV) dimensions, mean Z-score values were higher in SP. There was a significant Z-score increase in interventricular septum diastolic diameter (2.47z vs. 1.62z,p < 0.05), left ventricular posterior wall diastolic and systolic diameter (1.15z vs. 0.47z,p < 0.05 and 1.05z vs. - 0.4z,p < 0.05). Athletes had significant greater LV mass indexed for BSA (94 +/- 12 g/m(2)vs. 81 +/- 13 g/m(2),p < 0.05). There was no significant difference in LV function or diameters. Conclusion: Our findings suggest that elite soccer training in adolescent male is a type of sport predominantly related to cardiac resistance remodeling. Adolescent SP may develop supernormal left ventricular wall dimensions (+ 2.0 to + 2.5z). If in SP Z-scores, any LV dimension above + 2.5 is measured, primary or secondary cardiomyopathies should be excluded.What is Known:center dot Morphological cardiac adaptation in response to exercise depends on the type, duration, and intensity of training.center dot Morphological and functional changes due to competitive sports (athlete's heart) occur even in pre-adolescent athletes.What is New:center dot Our findings point out that German elite soccer training in adolescent male (10-14 years of age) is a type of sport predominantly related to cardiac resistance remodeling.center dot If in an adolescent competitive soccer player any LV dimension Z-score value above + 2.5 is measured, a primary or secondary cardiomyopathy should be excluded.