Noninvasive evaluation of world class athletes engaged in different modes of training.

This study evaluated by noninvasive methods the cardiac structure and functional characteristics of world class athletes participating in different types of training programs. Fourteen subjects, including 4 strength-trained (discus and shot put), 4 endurance-trained (long distance runners), 4 decathlon-trained (strength and endurance), 2 wheelchair athletes and 31 college-age control subjects were evaluated using electrocardiography, M-mode echocardiography and maximal oxygen consumption. M-mode echocardiography measurements of left ventricular structure and function were compared before and after normalization for lean body weight. As expected, endurance athletes had greater maximal O2 consumption than the other groups (p less than 0.05). Before normalization for lean body weight, there were no significant differences in end-diastolic dimensions. After normalization, the endurance, wheelchair and control subjects had end-diastolic dimensions larger than those of strength athletes. Strength athletes appeared to have a much larger posterior wall and septal thickness than all groups except the decathlon athletes. However, when normalized, there was no difference among any of the groups. Previous investigators have attempted to determine "normalcy" of cardiac hypertrophy by looking at the ratio of left ventricular wall thickness to left ventricular radius. In the present study, the thickness to radius ratio in strength athletes was 33% greater than that in endurance athletes. It appears that the left ventricular wall thickness in the strength athletes occurred without a concomitant increase in left ventricular radius and that the left ventricular hypertrophy of world class athletes is related to the total increase in lean body weight. However, ventricular dimensions may be related more to the type of overload experienced.

Heritability of cardiac size: an echocardiographic and electrocardiographic study of monozygotic and dizygotic twins.

Because of the uncertainty as to the extent to which cardiac size is determined by exercise training vs genetic endowment, this study investigated familial (genetic plus common family environment) vs nonfamilial influences on cardiac size. College-age monozygotic twins (group 1, 31 sets), dizygotic twins (group 2, 10 sets), siblings of like sex (group 3, six sets), and nonrelated subjects (group 4, 15 sets) underwent echocardiographic and electrocardiographic tests, measurement of maximum oxygen uptake (VO2max), and evaluation of pulmonary and body composition; mean intrapair differences of the four groups were compared. Mean intrapair differences in cardiac size varied as much for subjects in group 1 as for those in groups 2 and 3. However, subjects in groups 1, 2, and 3 had less variation (p less than .05) than those in group 4. After the initial testing, 14 pairs of monozygotic twins, five sets of dizygotic twins, and six sets of siblings underwent 14 weeks of exercise training (both members participated) and all tests were repeated. After exercise training, subjects in group 1 still had as much intrapair variability in cardiac size as those in groups 2 and 3. The data suggest cultural familial influences are more important in determining cardiac size than nonfamilial influences or even genetic influences alone.

Noninvasive evaluation of exercise training in college-age men.

The purpose of this study was to assess noninvasively the effects of intense aerobic training on cardiac structure and function in a group of healthy, college-age men (25 experimental and 11 control, mean age 22 years). Echocardiographic, electrocardiographic (ECG), and fitness measurements were obtained before and after a 3-month endurance training program and compared with similar measurements obtained in nonexercising subjects. The supervised training program consisted of 50-minute jogging sessions 5 days a week at 85% of maximal heart rate. Compared with the control group, echocardiography after training showed an increase in left ventricular (LV) end-diastolic dimension (p less than 0.05). LV posterobasal wall thickness, septal wall thickness and ejection fraction did not change significantly. ECG measurements revealed a decrease in resting heart rate (p less than 0.05) and an increase in R-wave voltage in leads V5 and V6 (p less than 0.01). The measured maximal oxygen consumption increased by 16% (p less than 0.001). These data indicate that intense aerobic training in college-age men results in a significant increase in resting LV end-diastolic dimension and volume. The increase in maximal stroke volume associated with exercise training may be partially explained by these changes in cardiac dimensions.