The developing athlete's heart: a cohort study in young athletes transitioning through adolescence

Athlete's heart is a term used to describe physiological changes in the hearts of athletes, but its early development has not been described in longitudinal studies. This study aims to improve our understanding of the effects of endurance training on the developing heart.

Cardiac morphology and function in 48 cross-country skiers were assessed at age 12 years (12.1 ± 0.2 years) and then again at age 15 years (15.3 ± 0.3 years). Echocardiography was performed in all subjects including two-dimensional speckle-tracking strain echocardiography and three-dimensional echocardiography. All participants underwent cardiopulmonary exercise testing at both ages 12 and 15 years to assess maximal oxygen uptake and exercise capacity.

Thirty-one (65%) were still active endurance athletes at age 15 years and 17 (35%) were not. The active endurance athletes had greater indexed maximal oxygen uptake (62 ± 8 vs. 57 ± 6 mL/kg/min, P < 0.05) at follow-up. There were no differences in cardiac morphology at baseline. At follow-up the active endurance athletes had greater three-dimensional indexed left ventricular end-diastolic (84 ± 11 mL/m² vs. 79 ± 10 mL/m², P < 0.05) and end-systolic volumes (36 ± 6 mL/m² vs. 32 ± 3 mL/m², P < 0.05). Relative wall thickness fell in the active endurance athletes, but not in those who had quit (-0.05 ΔmL/m² vs. 0.00 mL/m², P = 0.01). Four active endurance athletes had relative wall thickness above the upper reference values at baseline; all had normalised at follow-up.

After an initial concentric remodelling in the pre-adolescent athletes, those who continued their endurance training developed eccentric changes with chamber dilatation and little change in wall thickness. Those who ceased endurance training maintained a comparable wall thickness, but did not develop chamber dilatation.