Of the team ball games, water polo has the longest history in the Olympic Games; it was already on the program in Paris in 1900, and it has remained continuously on it until now. Other ball games were added to the program later. In water polo, Hungary has had a prominent role: Sydney was the seventh and Athens was the eighth time that Hungary won the gold medal during the history of the Games.
Of the main characteristics of water polo, we emphasize the very long sports career, very high intensity work, long training sessions, and a mixed exercise training program that includes an extremely high amount of strength training, as summarized by Smith (29).
Like ball game sports in general, water polo requires a mixture of power, speed, and endurance as well as a high level of technique/skill, tactical ability, finesse, and combat ability. However, all the movements must be carried out in a strange environment requiring special training. That is why a 4- to 5-yr-long swimming training program is necessary before beginning regular water polo training. Top-level players have, therefore, a very long sports training history.
Playing water polo requires greater physical strength than other ball games. During a game there is a direct body-to-body contact. Players grab each other and are very often involved in grappling, tackling, and wrestling activity. To develop their combat ability, players engage in regular strength training for 6–10 h·wk−1.
As the elements of the locomotor system are less prone to injuries in water, training sessions can take much longer than with various other dry-land ball games.
Due to the very strenuous nature of water polo, it seems reasonable that players have highly developed endurance capacity. Nevertheless, because of the game’s complexity and the unusual environment the interpretation of the commonly employed dry-land work capacity estimates (e.g., treadmill or bicycle ergometer) of athletic physical condition is problematic in water polo players. The aerobic power of water polo players in water has been estimated by some investigators by using head-out, tethered swimming (23,32). Similarly to several authors (summarized in the review of Smith (29)), we also used a relatively simple swim tests to determine the players’ physical condition (19).
High endurance capacity in athletes is usually accompanied by a very well developed athlete’s heart as demonstrated by several echocardiographic studies (10,21,22,31). We hypothesized that the properties associated with performance capacity in water polo players could be demonstrated by echocardiography in addition to V̇O2max studies.
The aim of the present study was to investigate how water polo influenced cardiac dimensions and aerobic power. To this end, echocardiographic and V̇O2max data were obtained in the Olympic champion water polo players. Their data were compared with those of top-level Hungarian endurance and power athletes, with nonathletic healthy subjects, and with results obtained for water polo players published by other authors (2,31,34).
MATERIALS AND METHODS
The water polo players were members of the Olympic champion team of Hungary. Two further players were added who had prepared with the team and were left out of the final team only 2 wk before the 2000 Games. All the players (N = 15) had trained intensely for over 9 yr. The measurements were made in February and March, 1999–2000; during this period, their training protocol included 25–30 h·wk−1, mostly swimming and water polo exercises, and 5–8 h·wk−1 of gym hall strength training.
The endurance athletes (N = 16) were six road racing cyclists, five pentathlonists, and five triathlonists. The power athletes were 11 weight lifters and four judoists, also members of the Hungarian national teams (N = 15). All athletes had been involved in a high-level regular physical training program for over 8 yr, the weekly amount of training being 8–22 h for power competitors and 25–35 h for endurance athletes. Healthy sedentary university students and young employees volunteered as nonathletic controls (N = 19). Written informed consent was obtained from all subjects before the investigations. The study was approved by the Ethical Committee at the National Institute for Sports Medicine.
Measurement of V̇O2max.
The exercise test was an all-out graded run performed on a Jaeger 6000 LE motor-driven treadmill at a belt speed of 12 km·h−1. The slope of the treadmill was increased by 2.5% every 2 min. Concentration and volume of oxygen and carbon dioxide in expired air was determined by a Jaeger-Dataspir device (Erich Jaeger GmbH & Co., Würzburg, Germany). It is noted that water sports athletes are not always able to reach their maximum aerobic power on a treadmill. In addition, scaling to body weight is not advantageous for muscular, bulky persons. In the present study aerobic power refers both to body mass (V̇O2max, mL·kg−1·min−1) and to body mass2/3 related maximal oxygen uptake (mL·(kg2/3)−1 ·min−1).
Investigations were always made at absolute rest. A Dornier AI 4800 (Germany) echocardiograph with a 2.5-MHz transducer was used. Two-dimensionally guided M-mode recordings were obtained parasternally in accordance with the recommendations of the American Society of Echocardiography (26); measurements of the left ventricular wall thicknesses and internal diameter were obtained by positioning the trackball cursor on the screen. All studies were performed by the same investigator (PG). Transmitral early and late diastolic peak filling velocities (E and A) were measured by pulse-wave Doppler obtained from the four-chamber apical view. The average of 5–10 cycles was used in the final analysis.
Left ventricular (LV) wall thickness (WT) was calculated as the sum of interventricular septum thickness (IVST) and posterior wall thickness (PWT). Left ventricular mass (LVM) was calculated by cubing the respective diameters (26) as LVM = [(IVST + PWT + EDD)3 − EDV] · 1.05, where EDD is left ventricular end diastolic diameter, EDV is end-diastolic volume = EDD3, and 1.05 is the density of the cardiac wall. The ratio of WT/EDD was calculated to characterize LV geometry.
As regards the reproducibility, in our laboratory, 148 subjects were examined two times within 1 yr at a similar heart rate. Averages (± SD) of the absolute values of IVST were 9.69 ± 1.40 and 9.61 ± 1.31, of the PWT 9.12 ± 1.26 and 9.23 ± 1.23, of the EDD 48.8 ± 4.11 and 48.9 ± 4.02 mm). Typical error of measurements (coefficient of variation) were 0.607 for IVST, 0.638 for PWT and 1.618 for EDD, intraclass correlation coefficients were 0.799 for IVST, 0.737 for PWT, and 0.841 for EDD.
According to several studies (5,13,20,21), when body size varies greatly, relative cardiac measures are correct only if the exponents of the numerator and the denominator for the respective body dimensions in the formula match. In studying the influence of body size on cardiac data, we used several body size scaling variables, but all indices were constructed according to the theory of geometric similarity (TofS) (15,27), that is, exponents of the numerator and denominator were matched. Cardiac measures on the first power (WT, EDD) were related to body height (BH), and the measure on the third power (LVMM) was related to body weight (BW). Preferring to keep indices related to body surface area (BSA) as well, in this study linear variables were related to the square root of body surface area (BSA0.5), whereas volumes and masses were related to the cube of its square root (BSA1.5) (20,21). BH and BM were used to estimate BSA according to the formula of Du Bois and Du Bois (9).
All statistical analyses were performed by using the STATISTICA 6.0 software. Group differences between the control and different athletic groups were analyzed via one-way ANOVA (independent groups) with Tukey post hoc tests, differences were accepted as significant at the 0.05 level.
Age and body size data are shown in Table 1. There was no difference in the age of the different groups. Height and body surface area (BSA) were significantly higher in the water polo players than in the other subjects. Their BW was also heavier than in the endurance athletes and nonathletic subjects.
Basic hemodynamic parameters and relative aerobic power are shown in the lower part of Table 1. Mean resting heart rate was lower in the water polo players and endurance athletes than in nonathletes. There were no differences in systolic blood pressure. Mean diastolic blood pressure was lower in the endurance athletes than in all the other groups. Body weight related mean aerobic power of the endurance athletes was higher than in all the other groups, and was higher in the water polo players than in the sedentary subjects. In the BW2/3 related aerobic power differences between all the groups were significant except the difference between power athletes and sedentary subjects.
Basic individual echocardiographic data of the water polo players are shown in Table 2. There were several players who demonstrated greater wall thickness than the classical critical value of 13 mm and a LV internal diameter greater than 60 mm, but none of the players displayed wall thickness or internal diameter larger than suggested for athletes of large body dimensions (wall thickness: 15–16 mm, internal diameter: 70 mm (22,33). IVST/PWT ratio was nearly 1 in all of the players (max. 1.09, min. 0.91).
Echocardiographic data are shown in Table 3. For IVST and WT water polo players showed the highest values followed by endurance athletes, power athletes, and by nonathletes. PWT and the calculated LVMM were higher in the water polo players than in all the other groups, whereas EDD was higher in them than in the power athletes and nonathletes.
Both BH and BSA related WT was greater in all athletic groups than in the sedentary controls, and was significantly higher in the water polo players than in the power athletes. BSA related WT in the endurance athletes was also higher than in the power athletes and nonathletes. BH related EDD was similar in all the groups, BSA related EDD was larger in the endurance athletes than in the power athletes and nonathletes. Both BW and BSA related LVMM was similar in the water polo players and endurance athletes, and higher than in the power athletes and the sedentary subjects. WT/EDD was higher in all athletic groups than in the nonathletes, and in the water polo players it was higher than in the power athletes.
The only difference in the fractional shortening was that the water polo players showed higher values than the power athletes. The E/A ratio was higher in the water polo players than in the other groups; the Tukey test, however, showed only a near to significant probability (P = 0.064).
The V̇O2max values of the Olympic champion water polo players were significantly lower than in the top-level endurance athletes, but higher than in the nonathletic controls, and similar to those of the soccer and basketball players in our previous investigations (28). Other authors reported similar or lower results from laboratory tests (1,7,14,25,29), while studies using pool performances reported similar or slightly better figures (12,29). The echocardiographic data of our water polo players, however, indicated very marked cardiac adaptive response.
Individual data of our water polo players (Table 2) demonstrate that these players had quite large LV wall thickness, and there were several players demonstrating a higher wall thickness than the 13 mm critical to cardiomyopathy. We must take into account, however, that these players have extremely large body dimensions, which, together with their very high amount of training activity probably explains their extremely large cardiac dimensions. Their body size related left ventricular measures were similar to those reported by other authors (10,22,33,34). Data of our players did not exceed the limits given for athletes recently: 15–16 mm for wall thickness and 70 mm for internal diameter (22). Suspicion of a pathological hypertrophy, that is, of cardiomyopathy appears negligible also by other data. Thus the IVST/PWT ratio never exceeded the critical limit of 1.3, and no other characteristics of cardiomyopathy, such as left atrial enlargement, impaired diastolic function, or bizarre ECG patterns, were seen (11).
Cardiac hypertrophy of the water polo players was manifest in the absolute and body size related LVWT and LVMM. Their absolute EDD was higher than in the power athletes and sedentary subjects. However, when EDD was expressed in terms of body size there were no significant differences between the water polo players and the other groups.
The proportion of the wall thickness to the internal diameter provides important information regarding the character of the cardiac hypertrophy and is expressed by the index WT/EDD. This index is termed relative wall thickness in some communications (10), and in other reports as muscular quotient (6) or hypertrophy index (33), and is generally used to demonstrate the eccentric or concentric character of LV hypertrophy. According to the observations of Morganroth et al. (18), endurance sports induce mostly the eccentric type whereas power sports bring about the concentric type of hypertrophy. Several reports (10,22,24) and our previous results (21) suggested, however, that the two types of hypertrophy cannot be clearly distinguished in training-induced myocardial hypertrophy. An increase in WT can be expected with any kind of regular physical training, and it can be even more marked with very extensive endurance work than with strength training, whereas an increase in EDD seems to be caused predominantly by endurance activity.
In our material, only the endurance athletes had significantly greater EDD/BSA0.5 than the power athletes and sedentary subjects. It can be assumed that the larger body size, mainly the taller height accounted in a great part for the larger EDD and the larger WT was the predominant feature in the water polo players.
In comparison with other subjects, the ratio WT/EDD was the highest in the water polo players. It differed significantly from the values of the power athletes and nonathletes; however, the difference from the endurance athletes was not negligible either (P = 0.0615). The very long sports career and extremely large amount of high-intensity training may explain why water polo players display higher WT/EDD than the mean of the power athletes, whereas the great share of strength elements in the game and the large amount of strength training may explain the difference from the endurance athletes.
Diastolic function can be reliably characterized by the E/A quotient, the ratio of the early to late diastolic filling velocity measured by Doppler echocardiography. Although ANOVA analysis showed no significant differences among the groups, it is interesting that the water polo players had an approximately 20% higher E/A quotient than the other groups. The E/A quotient is known to decrease due to pathologic cardiac hypertrophy, cardiomyopathy, or even normal aging (11). In such cases an increased WT/EDD ratio would be expected to be accompanied by a decreased E/A. On the other hand, high-level sports activity appears to have a positive effect on diastolic function not only in older subjects but also in young adults (16,17). Previous studies have suggested that endurance type sports are the most effective activities for improving diastolic function (8,21). The relatively high value of the E/A ratio in water polo players cannot be judged simply as a direct manifestation of the positive effect of water polo on the diastolic function, especially if we take into account that the lowest heart rate of the water polo players may contribute to their highest E/A. Our findings provide evidence that the hypertrophy of the heart induced as an adaptive response to water polo training is, in contrast to pathologic concentric hypertrophy, a favorable adaptation that results in improved cardiac function.
One of the best indicators of training has been the resting heart rate. Resting bradycardia was also the most marked in the water polo players, their resting heart rate was significantly lower than that of the power athletes and nonathletes.
We attempted to answer the question: whether this very high level of cardiac adaptation was generally applicable to water polo or was a specific characteristic of our Olympic champion athletes. The best way to answer this question is to compare our results with other data obtained from male water polo players. Table 4 compares our data with studies of other water polo teams (2,31,34). The LVM and related data of the other authors were recalculated to match our calculations. The control data of Caso et al. (2) and Zakynthinos et al. (34) were very similar to our data for sedentary persons so methodologically the data seem to be comparable (WT/BSA0.5 was 12.8 in the study of Caso et al. and in our material and 13.1 in the article of Zakynthinos et al.; EDD/BSA0.5 values were 35.1, 36.3, and 34.2 respectively).
BSA-related left ventricular measures of our water polo players were very similar to those of Zakynthinos et al. (34), LVWT and LVM were larger than in the study of Caso et al. (2) and Spirito et al. (31). As discussed by Zakynthinos et al. (34), it seems likely that the subjects in the latter two studies were not world class players.
For the absolute values of the E/A quotient, our results were a little higher than those of Caso et al. (2), but they were similar in that water polo players displayed a markedly higher (1.98) value than the control subjects (1.54). For the resting HR, our players showed the lowest values, and there were no differences in the shortening fraction.
If we compare our results with reports of other authors obtained from top-level athletes of other disciplines, we can establish that the cardiac measures of our water polo players are also representative of a high international level. Only some endurance athletes, especially road cycle racers, showed higher body size related LVWT and LVMM (4,30), ball game players showed similar (30) or smaller LV measures (3,30,31), and our water polo players also displayed higher values than top-level Hungarian basketball and soccer players (28).
Water polo is a special branch of sports because of a definitely long sports career of the athletes, an extremely high amount of training exercise, and the character of the exercise material combining endurance and strength elements. The specific features of top-level water polo are manifested in the players’ echocardiographic data: the extreme amount of training and the high-level endurance activity manifested itself in greater body size related wall thickness and left ventricular muscle mass than in power athletes; the strength component of their training and competitive program was associated with an even higher share of wall thickness than in the endurance athletes. In spite of this marked hypertrophy, no functional disturbance was seen in the water polo players.
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