ABSTRACTBackgroundIntensive training efforts are associated with hemodynamic changes accompanied by increases in cardiac output and stroke volume related to higher peak oxygen consumption and better athletic performance during exercise. These hemodynamic changes induce an enlargement of cardiac chambers, but also of the atria and may result in an athletes’ heart (AH). Data from large studies about atrial enlargement in AH are sparse.MethodsCompetitive athletes aged ≥18 years, who presented for pre‐participation screening 04/2020–10/2021 were included in this study and stratified for AH (defined as physiologically increased heart volume >13.0 in males and >12.0 mL/kg in females).ResultsOverall, 646 athletes aged ≥18 years (median age 24.0 [20.0/31.0] years; 206 [31.9%] females) were included in our study 04/2020–10/2021; among these, 118 (18.3%) had an AH. The computed absolute heart volume was 969.4 (853.1/1083.0) mL in athletes with AH and 841.3 (707.4/966.3) mL in those without AH (p < 0.001). AH was associated with larger left ventricular mass (206.6 ± 39.0 vs. 182.7 ± 44.2 g, p < 0.001). LA area (15.4 [13.7/18.2] vs. 14.3 [12.0/16.3] cm2, p < 0.001) and RA area (15.8 [13.8/18.6] vs. 14.5 [12.3/17.0] cm2, p < 0.001) were enlarged in AH versus those athletes without AH. The logistic regressions confirmed an independent association of AH on LV mass (OR 1.05 [95% CI 1.04–1.06], p < 0.001). LA area (OR 1.29 [95% CI 1.19–1.39], p < 0.001) as well as RA area (OR 1.28 [95% CI 1.19–1.38], p < 0.001) were afflicted by AH.ConclusionAn AH is accompanied by significant enlargement of the atria as well as increased cardiac muscle mass.