Before entering the study all subjects answered a questionnaire regarding their health, medication, and athletic history. One oarsman was treated for hypertension, which excluded him from the study. The remaining 30 subjects were free of symptoms related to the cardiovascular system and received no medication of cardiovascular consequence. None of the subjects had a family history of cardiac disease or premature cardiac death.
Two-dimensional and M-mode echocardiograms were recorded using a 3.5 MHz transducer (Toshiba, Japan). Left ventricular dimensions were obtained from M-mode recordings on the parasternal long axis view at the tip of the mitral valve (14). The following variables were recorded: left ventricle end-diastolic diameter (LVEDD), left ventricle end-systolic diameter(LVESD), septum thickness (ST), and posterior wall thickness (PWT). All echocardiograms were performed by the same investigator and recorded. Blinded off-line analysis of the echocardiograms was carried out by the same observer. For each echocardiographic parameter measurements were made from five representative cardiac cycles and a mean value was calculated.
The following formulas were used: relative wall thickness = PWT·2/LVEDD; fractional shortening = (LVEDD-LVESD)/LVEDD; left ventricular mass = 1.04·(LVEDD + PWT + ST)3 - LVEDD3)(2). Body surface area (BSA) was estimated using the formula of Du Bois (5).
On a separate day height and weight were recorded and a resting blood pressure and a 12-lead ECG were obtained. Subsequently, ergometer cycling was carried out with a work rate that was increased by 25 W every second minute until exhaustion. The ECG was continuously monitored and blood pressure measured every second minute and at the end of exercise. Horizontal or downsloping ST-segment depressions >1 mm were considered significant.
Values are median with range. Results were compared using the Mann-Whitney test. Interdependencies were evaluated by the Spearman test. A P value <0.05 was considered significant.
Between the two groups of subjects no significant differences in body weight or height were found (Tables 1 and 2). Median resting diastolic and systolic blood pressures were higher in the control group, but the differences were not significant. One oarsman had an elevated systolic blood pressure (200/85 mm Hg). The ECG at rest was normal in all control subjects (a criterion for enrollment in the population study), but a variety of abnormalities were recorded in the oarsmen: 1 AV-block(N = 2), incomplete right bundle branch block (N = 2), left ventricular hypertrophy without strain (N = 2), and one oarsman exhibited atrial fibrillation (resting heart rate: 79 beats·min-1).
The oarsmen reached a higher work rate than did the sedentary subjects(Table 1). The exercise ECG was normal in all control subjects. In the oarsmen no significant ST-segment changes were recorded during or following exercise. One oarsman exhibited ventricular premature complexes in bigeminy, which was normalized after the discontinuation of exercise.
The internal diameters of the left ventricle were similar in the two groups of subjects (Table 1). The septum and posterior wall thickness were larger for the oarsmen, and therefore the calculated left ventricular mass index was 19% larger. The left ventricular shortening fraction was higher in the oarsmen.
One oarsman exhibited a left ventricular mass of 597 g, as his septum thickness was 20 mm, the posterior wall thickness 10 mm, and the left ventricle end-diastolic diameter was 64 mm (Table 2). This subject did not exhibit elevated blood pressure (140/95 mm Hg), nor did the Doppler echocardiography reveal any cardiac valve dysfunction. Also, his systolic function appeared normal, as the shortening fraction was 0.28. If the statistical analysis on cardiac dimensions is made excluding this subject, the differences in septum thickness, posterior wall thickness, and left ventricular wall mass and index remain significant (P < 0.05). For the two groups of subjects no significant correlation was revealed between the left ventricular mass, or the relative left ventricular mass and the resting diastolic or systolic blood pressures.
Morphology of the left ventricle in young oarsmen (aged 17-36 yr) has been studied by others. Highly trained young oarsmen have greater left ventricular wall thickness and larger end-diastolic diameter than sedentary control subjects, whereas no difference in the shortening fraction was demonstrated(4,9,17). Furthermore, rowing is associated with a larger left ventricular mass than other sports. This results from the combination of both large internal diameters and wall thicknesses(4,13). Thus, 15 of 16 athletes (of 947) with a wall thickness ≥13 mm were oarsmen or canoeists (13). Also, in toplevel rowers left ventricular hypertrophy is further increased by 5 months of vigorous training (1).
Cardiac hypertrophy has been demonstrated in the senior long-distance runner (3,7) and cyclist(11,12,16), but no information is available on left ventricular hypertrophy in the oarsman of advanced age. Furthermore, only the study of Di Bello et al. (3) includes athletes of an age comparable to the subjects of this study. All these studies conclude that the left ventricular mass of active senior athletes exceeds that of an age-matched control group. However, some disagreement exists with respect to systolic function. Thus, in contrast to the other investigators, Nishimura et al. (12) detected a slightly depressed systolic function in cyclists aged 40-49 yr when compared with an age-matched sedentary control group.
In the present study left ventricular mass was considerably enlarged in the oarsmen, in particular because of a greater septum and posterior wall thickness. In contrast to the findings in the younger oarsmen(4,9,17), no left ventricular dilatation was demonstrated in the senior rowers. One may speculate that the less intense training performed by the senior oarsmen maintains the left ventricular wall hypertrophy, but fails to preserve the enlargement of the end-diastolic diameter. A tendency toward myocardial wall asymmetry, the septum being the larger, is noted in the oarsman group. As indicated, one oarsman in particular had a grossly enlarged septum, which suggests the diagnosis of hypertrophic cardiomyopathy. The calculated left ventricular mass of this individual should be interpreted with some caution, as the cube formula is less accurate when left ventricular symmetry is distorted (2).
We found that almost half of the oarsmen had abnormal resting ECG. It is well known that ECG abnormalities, including the ones observed in the oarsmen of the present study, are more frequently seen in athletes than in the normal population. These abnormalities do not necessarily imply cardiac disease in the asymptomatic athlete, but can be merely a manifestation of“athlete's heart” (8). Also, as exercise ECG was normal in all oarsmen, an overrepresentation of asymptomatic ischemic heart disease in the oarsman group would not likely explain the difference in cardiac size between the two groups.
One problem encountered in this study was the lack of equality in age between the oarsmen and the controls. Some investigators have found that ageper se is associated with an enlarged myocardial wall thickness. Thus, Gerstenblith et al. (6) detected an approximate increase of 0.04 mm·m-2·yr-1 for the posterior wall thickness in a normal aging population, although this is not a consistent finding (2). Yet, if such a correlation is taken into account, the impact of the age difference between the study groups on the posterior wall thickness would amount to no more than 0.24 mm·m-2 in this study. Thus, inequality in age would not sufficiently explain the difference observed. Therefore, we conclude that the well-trained senior oarsman has a high work capacity associated with increased myocardial thickness and a normal systolic function.
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ROWING; WORK CAPACITY©1996The American College of Sports Medicine