In the present work, we analyzed the anthropometric and body composition characteristics, nutrition habits, and laboratory parameters of athletes playing on the most successful Hungarian water polo team. The study was performed at the beginning of the championships and after the regular season. Each athlete had long training experience with international successes, as World championship, European Super Cup, Champions' League, and Olympic games. No scientific research has been published previously about the elite male FTC water polo team. Analysis on self-reported health status of the participants showed significant differences in numerous questions in the post-intervention period. Overall, their perceived health status and physical condition had changed in an unfavorable way. The explanation to this may be in connection with the increase in the number of matches during the competitive season, which requires high consistent athletic performance, and moreover, added mentally demanding technical and tactical elements to their everyday training.
We observed strong positive correlations between the anthropometric and body composition characteristics. The correlation between the body composition characteristics and the physical performance of handball players and swimmers had been studied [16, 17]. These studies found that body composition characteristics were associated with performance; therefore, these results can help the work of coaches to achieve more optimal sports performance for handball players and swimmers.
Due to the specific characteristics of water polo, results of other sports could not be directly applied. Thus, our results can be directly compared only with the results of other studies performed on water polo players. However, to the best of our knowledge, only a few studies have been published in this field. In a former study, Kondrič et al.  examined the anthropometric and body composition characteristics, physical condition and fitness of 110 junior water polo players with different playing positions. Based on their results, centers had significantly higher body weight, BMI, and larger subscapular skinfold compared to other players. In that study, the players’ physical condition was measured by swimming tests. They found that the shooters achieved the best test results in 25 m and 400 m sprints, but without significant differences . However, swimming tests are not suitable to describe the performance status of players during the training sessions and games, which both consist of technical and tactical components and thus require further skills. The swimming tests can characterize only the physical status of players. Unfortunately, the accurate monitoring of players during training and games is still unresolved, making it difficult to collect performance data.
In our analysis, using cluster analysis, we determined two significantly different clusters based on players’ anthropometric and body composition characteristics. Cluster I included goalkeepers and wingers, while Cluster II consisted of centers, shooters, and defenders. Cluster I players were 5 cm shorter on average, while their mean body weight, skeletal muscle mass and body fat mass data were lower by 19 kg, 7 kg and 7 kg, respectively, compared to height, body weight, skeletal muscle mass and body fat mass of players classified into cluster II. These results are consistent with the results described by Kondrič et al. and can be explained by the fact that the playing position of goalkeepers and wingers requires more dynamism, explosiveness and agility. In former studies, specific anthropometric differences of athletes in different playing positions have also been described for adult male elite water polo players. These studies have also confirmed that athletes playing in center or defender positions are taller and have the highest BMI within the team [18, 19]. These examples highlight significant anthropometric differences between playing positions and can give support to the development of position-specific training programs and thus, nutritional recommendations. In addition to the abovementioned results, we found a significant decrease in the mineral composition of athletes after the 4-month intervention period, which parameter represents the osseous and non-osseous mineral amounts. The decrease in the amount of minerals can be explained by the parallel decrease in vitamin D level, which has an impact on bone mass acquisition. On the other hand, the adequate protein intake is also assumed to support bone metabolism , which was lower than the recommended amount for athletes.
As performance might be strongly influenced by nutrition intake, the athletes’ dietary habits were also analyzed. Although we detected a slight differences in macronutrient consumption between the two clusters, they were not significant. However, we would like to suggest that nutrition recommendations should reflect the different physical- and, therefore, nutritional demands of Cluster I and II. We calculated that the athletes in Cluster II had higher daily protein, carbohydrate, and fat intake, which then resulted in higher overall calorie intake. Due to the high demands of elite sports, such as the high number of daily in-water and/or dryland conditioning trainings for water polo players, the level of blood sugar decreases during and/or after the exercises. Therefore, adequate carbohydrate intake can reduce the incidence of exercise-induced hypoglycemia. Muscle glycogen depletion depends on the duration and intensity of exercise, suggesting that the recommended daily carbohydrate intake for elite male athletes is 8–12 g/kg/day for optimal replenishment of glycogen stores [1, 2, 4]. Based on our results, rather alarmingly, athletes did not get close to this recommended carbohydrate intake, which was 2.09 g/kg/day in Cluster I and 2.87 g/kg/day in Cluster II. The daily protein intake also did not meet the recommended rate of 1.4–2.0 g/kg/day consumption in Cluster I, which means an average of 1.24 kcal/kg/day . According to the recommendations, athletes need to consume almost twice as much protein daily as the sedentary population to maintain appropriate protein synthesis and energy production. On the other hand, the required amount is given separately for athletes doing endurance or strength sport, as the intensity and length of training also influence the needs. In addition, optimal timing of protein intake has also an important role. It should be consumed before and after the training, and regularly 3–5 times during the day. Protein intake is especially noteworthy because the body is unable to store amino acids such as fatty acids or carbohydrates . The recommended fat intake is a maximum of 30% of the total daily calorie intake regardless of training intensity , which was appropriate in both clusters. The players’ fiber intake was also within the recommended range. In summary, lower carbohydrate and protein consumption was reported, particularly by athletes in Cluster I which suggests position-specific and/or personalized nutritional plans. However, in elite sports, it is regular for players to eat the same meal after training and matches, without paying attention to individual nutritional needs. A former study performed among elite woman volleyball players also showed that the daily average energy intake of athletes, including especially the carbohydrate consumption, was lower than the recommended amount . Therefore, it would be important for the players to receive personalized nutritional recommendations by experts. However, it is important to emphasize that these athletes achieved numerous international victories regardless the above-mentioned nutritional results. Therefore, the international nutritional recommendations should be treated with caution. In the literature, no position-specific nutritional recommendation for water polo players has been described, however the differences in anthropometric and body composition parameters highlighted the need for more specific recommendations. In the present study, the number of athletes stratified by playing positions is limited, therefore, we would like to extend the analysis to more water polo teams from Hungary. In the future, we would like to focus much more on the individual nutritional requirements of athletes according to their playing positions, considering the actual training length and intensity.
Nutritional deficiencies can be identified by monitoring laboratory parameters. During the 4-month research period, the strength endurance training was replaced with more tactical training and games. In line with this, after the end of the regular season, we detected an elevated level of triglyceride, uric acid, and potassium, and a decreased level of creatinine kinase. In addition, we measured a slightly decreased levels of urea and Vitamin D (p < 0.1). A higher triglyceride level might be caused by the relatively higher fat intake (5.44 g/kg/day), while significantly higher uric acid level by the higher training volume and exercise intensity . The high potassium concentration in the blood is a response to muscle contraction and therefore also associated with higher training volume . The insufficient protein intake can also be determined with the low urea level, while the decreased level of vitamin D may be associated with the overload of players. Vitamin D has an effect on muscle activity, a deficiency which can cause weakness and influence recovery time after exercise. Therefore, relevant vitamin intake is needed to achieve the optimal athletic performance [12, 25]. We examined the correlation between the initial anthropometric and body composition parameters and changes in laboratory parameters before and after the championship. We detected different pattern in the changes in glucose and magnesium between the two clusters. Higher glucose level may be occurred by higher carbohydrate consumption in cluster II. These results may confirm the differences between the two clusters, however further analyses are needed to reveal the factors caused the differences, which was observed mostly in cluster II.