The long-term involution of physiological cardiomegaly and cardiac hypertrophy. Med. Sci. Sports Exerc., Vol. 21, No. 3, pp. 244-249, 1989. Forty-five former athletes in endurance disciplines, primarily Olympic medalists and World Cup, European Cup, and German champions, for whom results of an exercise ECG and radiological heart volume measurement were available from their active competitive phase, were examined. The study protocol included clinical examination, laboratory controls, resting and exercise ECG, determination of cardiac volume, and one- and two-dimensional echocardiographic examination. Of the 45 former athletes contacted, 38 appeared for examination. Of these, four presented with heart disease (two with infarction, one with aortic stenosis, and one with arrhythmia). The remaining 34 were divided into groups of still active (more than 300 kcal.wk-1) and inactive (less than 300 kcal.wk-1) athletes. The interval between the first and second examination averaged 23 yr. The active former athletes showed a weight increase of 5.2% (P less than 0.01) and a reduction of 14% in ergometric performance (P less than 0.02). The inactive group had a marked weight increase of 17.4% (P less than 0.001); the ergometric performance was lowered by 20% (P less than 0.001). The absolute heart size had decreased in the active group by 6.1% (NS) and the relative heart size by 10.7% (P less than 0.005); the corresponding values in the inactive group were 4.5% (NS) and 18% (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)