Noninvasive assessment of seasonal variations in cardiac structure and function in cyclists.

Noninvasive studies were performed in 12 male bicylists in the competitive season (CS) and in the resting season (RS) and in 12 matched control subjects to determine seasonal variations in cardiac structure and function in athletes and to compare the data with those of nonathletes.In athletes, peak oxygen uptake was 6% lower in the RS than the CS; the RS value was 40% higher than in nonathletes.The echocardiograms of athletes showed a higher left ventricular total diameter at end-diastole in the CS than in the RS; this difference was due to a greater septal and posterior wall thickness, with unchanged internal diameter.On the ECG, R-wave voltages were larger in the CS in leads I, V5 and V6.Athletes had greater left ventricular dimension and wall thickness than nonathletes, and their ratio of wall thickness to internal radius of the left ventricle was higher.Various echo-and mechanocardiographic indexes of left ventricular function were determined.During the RS, the athletes had a lower percent shortening and maximal velocity of left ventricular internal diameter, lower maximal and minimal velocities of the endocardium of the posterior wall, a longer preejection period and a larger ratio of preejection period to left ventricular ejection time.These findings are probably related to a greater left ventricular end-systolic stress, an index of myocardial afterload, in the RS.We conclude that cyclists in the CS, compared with nonathletes, have greater left ventricular internal dimension and increased wall thickness, with similar left ventricular function.During the RS, internal dimension does not change from the level in the CS, but wall thickness is somewhat reduced and left ventricular function is slightly depressed, most likely because of a higher afterload in RS.ENDURANCE TRAINING induces changes in cardi- ac structure, as revealed by the comparison of the hearts of athletes with those of nonathletesl-'0 and by longitudinal studies in which athletes'0 and nonath- letes'2-' are followed during training.Whereas radio- logic examination of the chest can only demonstrate overall enlargement of the heart of endurance athletes, echocardiographic studies (except one3) reveal that the left ventricular (LV) internal diameter is significantly increased," 2. 10 with an increase of septal and posterior wall thickness in most,2' 3 5 6, 9 10 but not all, re- ports. 1 4 7' Calculated muscle mass was greater in ath- letes.Endurance training of nonathletes may affect LV dimension and wall thickness,'21'3 although not consis- tently. 14' 1 ' Such differences are associated with higher voltages on the ECG in athletes5 6 r 9.in nonathletes after training.'2-14The structural adaptation of the heart allows the generation of a higher stroke volume, which permits a higher maximal cardiac output and oxygen uptake.1" Some studies using echocardiography5 6-12 or systolic time intervals'8 also suggest that ventricular performance is enhanced in athletes or in response to training, but others do not agree,2 4 8-11 13 15 or even report depressed LV function.3In most studies, athletes in their active season are compared with non-or less active subjects.