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Wetenschap en waterpolo

Brain natriuretic peptide predicts forced vital capacity of the lungs, oxygen pulse and peak oxygen consumption in physiological condition.
Peptides. 2013 Feb 16. pii: S0196-9781(13)00041-7. doi: 10.1016/j.peptides.2013.01.017.  
Popovic D, Ostojic MC, Popovic B, Petrovic M, Vujisic-Tesic B, Kocijancic A, Banovic M, Arandjelovic A, Stojiljkovic S, Markovic V, Damjanovic SS.
Division of Cardiology, Faculty of Medicine, University of Belgrade, Visegradska 26, 11000 Belgrade, Serbia.

Brain natriuretic peptide (NT-pro-BNP) is used as marker of cardiac and pulmonary diseases. However, the predictive value of circulating NT-pro-BNP for cardiac and pulmonary performance is unclear in physiological conditions. Standard echocardiography, tissue Doppler and forced spirometry at rest were used to assess cardiac parameters and forced vital capacity (FVC) in two groups of athletes (16 elite male wrestlers (W), 21 water polo player (WP)), as different stress adaptation models, and 20 sedentary subjects (C) matched for age. Cardiopulmonary test on treadmill (CPET), as acute stress model, was used to measure peak oxygen consumption (peak VO2), maximal heart rate (HRmax) and peak oxygen pulse (peak VO2/HR). NT-pro-BNP was measured by immunoassey sandwich technique 10min before the test - at rest, at the beginning of the test, at maximal effort, at third minute of recovery. FVC was higher in athletes and the highest in W (WP 5.60±0.29 l; W 6.57±1.00 l; C 5.41±0.29 l; p<0.01). Peak VO2 and peak VO2/HR were higher in athletes and the highest in WP. HRmax was not different among groups. In all groups, NT-pro-BNP decreased from rest to the beginning phase, increased in maximal effort and stayed unchanged in recovery. NT-pro-BNP was higher in C than W in all phases; WP had similar values as W and C. On multiple regression analysis, in all three groups together, ?NT-pro-BNP from rest to the beginning phase independently predicted both peak VO2 and peak VO2/HR (r=0.38, 0.35; B=37.40, 0.19; p=0.007, 0.000, respectively). NT-pro-BNP at rest predicted HRmax (r=-0.32, B=-0.22, p=0.02). Maximal NT-pro-BNP predicted FVC (r=-0.22, B=-0.07, p=0.02). These results show noticeable predictive value of NT-pro-BNP for both cardiac and pulmonary performance in physiological conditions suggesting that NT-pro-BNP could be a common regulatory factor coordinating adaptation of heart and lungs to stress condition.

The use of contact lenses during water-polo play: A 20-year study of Japanese college players.
J Sports Sci. 2013 Mar;31(6):607-11. doi: 10.1080/02640414.2012.742957. 9.
Komori Y, Kobayashi D, Murase Y, Enomoto I, Takagi H, Kono I.
a Doshisha University , Faculty of Health & Sports Science , Kyotanabe , Japan.

This study investigated the extent of contact-lens use in Japanese college water-polo male players over 20 years (1991-2011, once every five years). Information about the use of contact lenses during play and the types of contact lens was obtained through a self-report questionnaire. The proportion of contact lens use among the players while playing water polo differed from 1991 to 2011 (?(2)(4) = 25.28, P < 0.001, Cohen's d = 0.63). Fifty-four per cent of the players used contact lenses while playing in 1991 (P < 0.001); more than 74% in 1996; 89% in 2001; 84% in 2006; and 86% in 2011. While 96% of the contact lenses used by the players in 1991 were the soft type, 74%, 92%, 86%, and 88% of the contact lenses used in 1996, 2001, 2006, and 2011, respectively, were the disposable type. These findings indicated a high percentage of players were using contact lenses while playing water polo between 1996 and 2011. This could be because the majority of players used disposable lenses. The results suggest that increasing use of contact lenses by water-polo players is beneficial.

The Validity of Session-RPE Method for Quantifying Training Load in Water Polo.
Int J Sports Physiol Perform. 2013 Nov 13.
Lupo C, Capranica L, Tessitore A.

PURPOSE: The assessment of internal training load (ITL) using the session rate of perceived exertion (session-RPE) has been demonstrated to provide valuable information, also in team sports. Nevertheless, no studies investigated the use of this method during youth water polo training. Thus, the aim of this study was to evaluate youth water polo training, showing the correspondent level of reliability of the session-RPE method.
METHODS: Thirteen male youth water polo players (age, 15.6 ± 0.5 y; stature, 1.80 ± 0.06 m; body mass, 72.7 ± 7.8 kg) were monitored during 8 training sessions (80 individual training sessions) within 10-days. The Edwards summated heart rate zone method was used as a reference measure of internal training load; the session-RPE rating was obtained using CR-10 scale modified by Foster. The Pearson product-moment was applied to regress the Edwards' heart rate zone method against CR-10 session-RPE for each training session and individual data.
RESULTS: Analyses reported overall high (r=0.88; R2=0.78) and significant (P<0.001) correlations between Edwards's heart rate and session-RPE methods. Significant correlations were also shown for each training session (r range: 0.69-0.92; R2 range: 0.48-0.85, P<0.05) and individual data (r range: 0.76-0.98; R2 range: 0.58-0.97, P<0.05).
DISCUSSION: The present results confirmed the session-RPE method as an easy and reliable tool to evaluate ITL in youth water polo, allowing coaches to efficiently monitor their training plans.

Intra-Individual Movement Variability Within the 5 m Water Polo Shot.
J Appl Biomech. 2013 Dec 17
Taylor P, Landeo R, Coogan J.

The purpose of this study was to explore movement variability of throwing arm and ball release parameters during the water polo shot and to compare variability between successful (hit) and unsuccessful (miss) outcomes. Seven injury free, sub-elite, females completed 10 trials of the 5 m water polo penalty shot. Intra-individual coefficient of variation percentage (CV%) values were calculated for elbow and wrist angular displacement, wrist linear velocity and ball release parameters (height, angle and velocity). Coordination variability (elbow/wrist angular displacement) was calculated as the CV% of the mean cross-correlation coefficient. Elbow and wrist displacement variability decreased to 80% of throwing time then increased toward release. Wrist linear velocity variability reduced toward release. Individual CV% values ranged between 1.6 - 23.5% (all trials), 0.4 - 20.6% (hit) and 0.4 - 27.1% (miss). Ball release height and velocity variability were low (< 12%; all trials) while release angle variability was high (>27%; all trials). Cross-correlation results were inconclusive. Roles of the elbow and wrist in production of stable ball release height and velocity and control of the highly variable release angle in the water polo shot are discussed and suggested for further study. Optimal levels of variability warrant future investigation.

Ten days of simulated live high:train low altitude training increases Hbmass in elite water polo players.
Br J Sports Med. 2013 Dec;47 Suppl 1:i70-3. doi: 10.1136/bjsports-2013-092746.
Garvican-Lewis LA, Clark SA, Polglaze T, McFadden G, Gore CJ.

OBJECTIVES: Water polo requires high aerobic power to meet the demands of match play. Live high:train low (LHTL) may enhance aerobic capacity at sea level. Before the Olympics, the Australian women's water polo team utilised LHTL in an attempt to enhance aerobic fitness.
METHODS: Over 6 months, 11 players completed three normobaric LHTL exposures (block 1:11 days at 3000 m; block 2+3:9 days at 2500 m, 11 days normoxia, 10 days at 2800 m). Haemoglobin mass (Hbmass) was measured through carbon monoxide-rebreathing. Before each block, the relationship between Hbmass and water polo-specific aerobic fitness was investigated using the Multistage Shuttle Swim Test (MSST). Effect size statistics were adopted with likely, highly likely and almost certainly results being >75%, >95%, >99%, respectively. A Pearson product moment correlation was used to characterise the association between pooled data of Hbmass and MSST.
RESULTS: Hbmass (mean ± SD, pre 721 ± 66 g) likely increased after block 1 and almost certainly after block 2+3 (% change; 90% confidence limits: block 1: 3.7%; 1.3-6.2%, block 2+3: 4.5%; 3.8-5.1%) and the net effect was almost certainly higher after block 2+3 than before block 1 (pre) by 8.5%; 7.3-9.7%. There was a very large correlation between Hbmass (g/kg) and MSST score (r=0.73).
CONCLUSIONS: LHTL exposures of <2 weeks induced approximately 4% increase in Hbmass of water polo players. Extra Hbmass may increase aerobic power, but since match performance is nuanced by many factors it is impossible to ascertain whether the increased Hbmass contributed to Australia's Bronze medal.

Technical, perceptual and motor skills in novice-expert water polo players: an individual discriminant analysis for talent development.
J Strength Cond Res. 2013 Dec;27(12):3436-44. doi: 10.1519/JSC.0b013e318298d48f.
D'Ercole AA, D'Ercole C, Gobbi M, Gobbi F.

The 4 tasks (A, B, C, and Y) have the characteristic of containing one more element than the task performed before it. In fact, task B introduces the slalom which is not present in task A. Task C introduces the ball control that are not present in tasks A and B, whereas task Y introduces the slalom and ball control in a visual dual task situation developed in horizontal swimming over a distance of 20 m at maximum speed. This exercise not included in task C. These tasks were performed by a group of pre-adolescent players and national under 18 water polo players. The novice players showed that tasks B and C are predictors of task Y. Such characteristics were not present in the expert players. The novice players also had difficulty in performing task Y because of the visual-attention overload, a difficulty that was not present in the expert players. To improve the 4 skills, the coach of the novice players developed a technical-didactic program, which was checked 6 months after the pretest. The posttest was not significantly different from the pretest while the individual discriminant analysis identified the improvements in some novice players, which on elaboration proved significant, enabling us to distinguish 2 subgroups, one with higher learning rates and the other with lower learning rates. In the practical applications, we describe the didactic tools (task analysis) and the different levels of development of technical skills in water polo. Improvements in these skills are explained through computational models like the HMOSAIC (Hierarchical, Modular, Selection and Identification for Control) while the individual discriminant analysis enables us to do a longitudinal analysis that is not possible with cross-sectional models.