Wetenschap en waterpolo


Antioxidant status of interval-trained athletes in various sports.
Int J Sports Med. 2006 Feb;27(2):112-6.
Dékány M, Nemeskéri V, Györe I, Harbula I, Malomsoki J, Pucsok J.
National Institute of Sport Medicine, Research Department, Budapest, Hungary.

Muscular exercise results in an increased production of free radicals and other forms of reactive oxygen species (ROS). Further, developing evidence implicates cytotoxins as an underlying etiology of exercise-induced stimuli in muscle redox status, which could result in muscle fatigue and/or injury. Two major classes of endogenous protective mechanisms (enzymatic and nonenzymatic antioxidants) work together to reduce the harmful effects of oxidants in the cell. This study examined the effects of acute physical exercise on the enzymatic antioxidant systems of different athletes and comparison was made to the mechanism of action of three main antioxidant enzymes in the blood. Handball players (n = 6), water-polo players (n = 20), hockey players (n = 22), basketball players (n = 24), and a sedentary control group (n = 10 female and n = 9 male) served as the subjects of this study. The athletes were divided into two groups according to the observed changes of activity of superoxide dismutase enzyme. The antioxidant enzyme systems were characterized by catalase (CAT), glutathione-peroxidase (GPX), and superoxide-dismutase (SOD) and measured by spectrophotometry. An important finding in the present investigation is that when the activities of SOD increased, the activities of GPX and CAT increased also and this finding related to the physical status of interval-trained athletes. Positive correlation between SOD and GPX activities was observed (r = 0.38 females, r = 0.56 males; p < 0.05). We have observed that the changes in the primary antioxidant enzyme systems of athletes are sport specific, and different from control subjects. Presumably, with interval-trained athletes, hydrogen-peroxide is significantly eliminated by glutathione-peroxidase. From these results it can be concluded that the blood redox status should be taken into consideration when establishing a fitness level for individual athletes.

Muscle-contraction properties in overarm throwing movements.
J Strength Cond Res. 2006 Feb;20(1):117-23.
Grezios AK, Gissis IT, Sotiropoulos AA, Nikolaidis DV, Souglis AG.
Laboratory of Biomechanics, Department of Physical Education and Sport Sciences, Aristotelian University of Thessaloniki, Thessaloniki, Greece.

On the basis of dynamic and kinematic data, this study identifies the type of muscle contraction in unloaded overarm throwing movements. An unloaded throw or nearly unloaded throw is defined as the throw in which the external resistance is too small (e.g., the team handball, baseball, and water polo throws as well as the tennis and badminton smashes). A special arm-force-measuring apparatus was constructed to imitate an overarm throw. Forty-two subjects were placed into 3 groups: untrained subjects, weight-trained athletes, and team handball players. The measured parameters included the velocity of the initial movement, the release velocity, the velocity of the first 50 milliseconds of the concentric phase, the force value at the moment of deceleration of the initial movement, and the impulse values during the eccentric and concentric phases of the test movement. Statistically significant higher values of the above parameters (p < 0.05) were determined in that test at which the initial speed of movement was higher. Also, the correlation coefficients of the parameters of the initial phase of the throw movement were very high (p < 0.001), especially the parameters related with the movement's first 50 milliseconds. The results support the thesis that the stretch-shortening cycle is the type of muscle contraction in unloaded overarm throws. Furthermore, it is possible to increase the throw velocity by increasing the velocity of the initial movement (i.e., by provoking higher inertia forces).

The water-polo intermittent shuttle test: a match-fitness test for water-polo players.
Int J Sports Physiol Perform. 2006 Mar;1(1):27-39.
Mujika I, McFadden G, Hubbard M, Royal K, Hahn A.
Dept of Physiology, Australian Institute of Sport, Canberra, Australia.

PURPOSE: To develop and validate an intermittent match-fitness test for water-polo players.
METHODS: Eight male junior players performed the Water Polo Intermittent Shuttle Test (WIST) twice to assess test reliability. To assess test sensitivity and validity, 104 male and female players from different competition standards and playing positions were tested. Eighteen players performed the WIST 5 times throughout a season to track fitness changes. Twelve players performed the WIST 48 hours before 4 consecutive National League games, and coaches awarded individual match-fitness scores based on game performances to assess the relationship between match fitness and test results. Heart rate (HR) and blood lactate (La(blood)) were measured during and after each test, respectively. Results: Test-retest performance values were 216 +/- 90 vs 229 +/- 96 m (r = .98, P = .0001, coefficient of variation [CV] = 5.4%), peak HR 190 +/- 8 vs 192 +/- 10 bpm (r = .96, P = .0002, CV = 1.2%), and La(blood) 7.0 +/- 1.8 vs 6.4 +/- 1.6 mmol/L (r = .84, P = .0092, CV = 8.8%). Significant differences were observed among different standards of play (range junior regional females 102 +/- 10 m, senior international males 401 +/- 30 m) and playing positions (field players 305 +/- 154 m, center forwards 255 +/- 118, goal keepers 203 +/- 135 m). Test performance was lower in the early season (344 +/- 118 m) than the remainder of the season (range 459 +/- 138 to 550 +/- 176 m). WIST performance and match-fitness scores correlated for all field players (r = .57, P = .054) but more highly for field players other than center forwards (r = .83, P = .0027).
CONCLUSIONS: The WIST is a reliable, sensitive, and valid match-fitness test for water-polo players. It could become a useful tool to assess the effects of different interventions on match fitness.

Self-determination in sport commitment
Percept Mot Skills. 2006 Apr;102(2):405-20
Zahariadis P, Tsorbatzoudis H, Alexandris K.
Sport Psychology Laboratory, Aristotle University of Thessaloniki, Greece.

The study tested utility of self-determination and sport commitment theories to understanding young athletes' sport commitment. 343 young athletes (M= 13.5 yr., SD= +/- 1.1) from soccer, basketball, volleyball, handball, and water polo teams volunteered to participate. All completed the Sport Motivation Scale and the Sport Commitment Questionnaire. Pearson correlations showed a strong relationship between commitment and intrinsic motivation scores. In contrast, extrinsic motivation scores were not significantly correlated to commitment, whereas amotivation scores showed a negative correlation to commitment. Path analysis resulted in strong positive association of intrinsic motivation and commitment. Amotivation had small negative relation to commitment. According to the model tested, social constraints and involvement opportunities were not significant contributors to sport commitment. An alternative model supported the mediating role of enjoyment to psychological commitment. The results showed that high self-determination is supportive of sport commitment, whereas low self-determination reduces sport commitment.

Injuries in team sport tournaments during the 2004 Olympic Games.
Am J Sports Med. 2006 Apr;34(4):565-76
Junge A, Langevoort G, Pipe A, Peytavin A, Wong F, Mountjoy M, Beltrami G, Terrell R, Holzgraefe M, Charles R, Dvorak J.
Fédération International de Football Association-Medical Assessment and Research Centre, Zurich, Switzerland.

BACKGROUND: Several authors have analyzed the incidence of injuries in a given sport, but only a few have examined the exposure-related incidence of injuries in different types of sports using the same methodology.
PURPOSE: Analysis of the incidence, circumstances, and characteristics of injuries in different team sports during the 2004 Olympic Games.
STUDY DESIGN: Cohort study; Level of evidence, 2.
METHODS: During the 2004 Olympic Games, injuries in 14 team sport tournaments (men's and women's soccer, men's and women's handball, men's and women's basketball, men's and women's field hockey, baseball, softball, men's and women's water polo, and men's and women's volleyball) were analyzed. After each match, the physician of the participating teams or the official medical representative of the sport completed a standardized injury report form. The mean response rate was 93%.
RESULTS: A total of 377 injuries were reported from 456 matches, an incidence of 0.8 injuries per match (95% confidence interval, 0.75-0.91) or 54 injuries per 1000 player matches (95% confidence interval, 49-60). Half of all injuries affected the lower extremity; 24% involved the head or neck. The most prevalent diagnoses were head contusion and ankle sprain. On average, 78% of injuries were caused by contact with another player. However, a significantly higher percentage of noncontact (57%) versus contact injuries (37%) was expected to prevent the player from participating in his or her sport. Significantly more injuries in male players (46%) versus female players (35%) were expected to result in absence from match or training. The incidence, diagnosis, and causes of injuries differed substantially between the team sports.
CONCLUSION: The risk of injury in different team sports can be compared using standardized methodology. Even if the incidence and characteristics of injuries are not identical in all sports, prevention of injury and promotion of fair play are relevant topics for almost all team sports.

Preliminary validation of a Spanish version of the Sport Motivation Scale.
Percept Mot Skills. 2006 Jun;102(3):919-30.
Núńez JL, Martín-Albo J, Navarro JG, González VM.
Department of Psychology and Sociology, University of Las Palmas de Gran Canaria, Spain.

The Sport Motivation Scale was developed in French and later translated into English and validated by Pelletier, et al. in 1995. It is based on the principles of self-determination theory. In this study the scale was translated into Spanish to assess and validate it for a sample of 275 athletes (78 women and 197 men) whose mean age was 21.3 yr. (SD=3.8) and who represented eight sports (track and field, tennis, swimming, waterpolo, soccer, basketball, handball, and volleyball). The Spanish version showed satisfactory internal consistency (Cronbach alpha of .70 to .80) and temporal stability (test-retest r = .69 to .74) over a 4-wk. period. A confirmatory factor analysis partially supported the seven-factor structure. Correlations among the subscales indicated a simplex pattern supporting the construct validity of the scale. Sex differences were found. Taken together, these findings support use of the Spanish version for assessment of motivation in sport.

Evaluation of the medial elbow in the throwing athlete.
Am J Orthop. 2006 Jun;35(6):266-9.
Creighton RA, Bach BR Jr, Bush-Joseph CA.
Department of Orthopaedic Surgery, University of North Carolina, Chapel Hill, North Carolina, USA.

The valgus forces generated by throwing athletes can cause injuries and permanently damage the medial elbow structures. Clinicians must have a clear understanding of the ulnar collateral ligament complex and the associated medial elbow structures at risk in these athletes. Taking a detailed history, conducting a physical examination, and obtaining imaging studies will aid in making the correct diagnosis and giving these injuries the appropriate treatment. Pain around the medial elbow is of concern to throwing athletes, coaches, and medical staff. Valgus forces generated by the throwing motion add considerable stress to the medial elbow structures and thus potentially cause injury. Baseball players, particularly pitchers, are most often affected, but athletes participating in sports such as football, volleyball, water polo, tennis, and javelin throwing can also be affected.

Water polo is associated with an apparent redistribution of bone mass and density from the lower to the upper limbs.
Eur J Appl Physiol. 2006 Jun;97(3):316-21.
Kavouras SA, Magkos F, Yannakoulia M, Perraki M, Karipidou M, Sidossis LS.
Laboratory of Nutrition and Clinical Dietetics, Department of Nutrition and Dietetics, Harokopio University, 70 El. Venizelou Avenue, Athens, 176-71, Greece.

The bone response to exercise is site-specific and load-dependent. Recent evidence suggests that an inverse relationship may exist between loaded and unloaded sites, such that the former may benefit at the expense of the latter. The present study examined this possibility in 48 males (21 water polo players, 12 handball players, and 15 sedentary controls). Water polo and handball are alike with respect to the active loading of the upper limbs during overhead throwing; however, the weight-supporting environment of water polo removes the weight-bearing effect from the lower limbs. Bone mineral content (BMC), bone projected area (Ap), and areal bone mineral density (aBMD) of the total body and of various subregions were determined by dual-energy X-ray absorptiometry. After adjusting for age, height, and weight, water polo players had higher arms BMC, Ap, and aBMD (by 22.2, 11.1, and 10.5%, respectively; P<0.05), but lower legs aBMD (-6.3%; P<0.05) relative to controls. On the contrary, compared to controls, handball players had higher BMC (from 11.8 to 24.3%), Ap (from 5.2 to 11.7%), and aBMD (from 6.4 to 11.9%) for the total body at all sites. Water polo athletes had increased arms and decreased legs aBMD ratios (regional-to-total) than either handball players or sedentary subjects (P<0.001). Water polo is associated with an apparent redistribution of bone mass and density from the lower to the upper limbs, with no major effects on the rest of the body.

Contact sports, moral functioning and planned behaviour theory.
Percept Mot Skills. 2006 Aug;103(1):131-44.
Bebetsos E, Konstantoulas D.
Department of Physical Education and Sport Sciences, Democritus University of Thrace, Komotini, Hellas.

The goal was to test the psychometric properties of the Moral Functioning Scale in a Greek athletic context, and to investigate any possible relation between moral functioning and planned behaviour. The sample comprised 384 athletes, 103 from the sport of football (soccer), 97 from basketball, and 184 from water polo. To measure moral functioning the researchers used a scale developed by Gibbons, Ebbeck, and Weiss. Planned Behaviour was assessed with a questionnaire based on Planned Behaviour Theory. Hierarchical regression analysis indicated strong association for Attitudes, Intention, Role Identity, and Perceived Behavioural Control with the four dilemmas of the moral functioning scale. The moral reasoning measure is a promising tool for measuring athletes' moral dilemmas in Greece.

The effects of fatigue on decision making and shooting skill performance in water polo players.
J Sports Sci. 2006 Aug;24(8):807-15.
Royal KA, Farrow D, Mujika I, Halson SL, Pyne D, Abernethy B.
Skill Acquisition, Athlete and Coach Services, Australian Institute of Sport, Belconnen, ACT, Australia.

The aim of this study was to assess the effects of fatigue on decision making and goal shooting skill in water polo. Fourteen junior elite male players (age 17.2 +/- 0.5 years; mass 84.2 +/- 7.6 kg; height 1.85 +/- 0.05 m) completed four sets of eight repetitions of an approximately 18 s maximal water polo specific drill. Progressively declining rest ratios for each successive set of the drill were employed to induce increasing fatigue and reflect the demands of match-play. A video-based temporally occluded decision-making task (verbalized response to various tactical situations) or goal shooting skill test (qualitative and quantitative analysis of goal shooting) was performed after each set. Heart rate, rating of perceived exertion (RPE) and blood lactate concentration were recorded. Heart rate (159 +/- 12, 168 +/- 13, 176 +/- 12, 181 +/- 12 Deats min-1; P < 0.001) and RPE (13.1 +/- 2.2, 15.5 +/- 1.7, 17.3 +/- 1.6, 19.1 +/- 1.1; P < 0.001) increased with declining rest ratios. At very high fatigue, decision-making accuracy was 18.0 +/- 21.8% better than at low fatigue (P = 0.008). Shooting accuracy and velocity were unaffected by incremental fatigue; however, skill proficiency (technique) decreased by 43 +/- 24% between the pre-test and high-fatigue conditions (P < 0.001). In conclusion, incremental increases in fatigue differentially influenced decision making (improved) relative to the technical performance (declined), accuracy and speed of the ball (unchanged) of a water polo goal shot.

A Cumulative Effect of Physical Training on Bone Strength in Males.
Int J Sports Med. 2006 Nov 16;
Falk B, Galili Y, Zigel L, Constantini N, Eliakim A.
Ribstein Center for Sport Medicine Sciences and Research, Wingate Institute, Netanya, Israel.

Weight-bearing, high-impact exercise, as opposed to nonimpact exercise, has been demonstrated to increase bone mineral density. This was traditionally demonstrated with dual energy X-ray absorptiometry. Our objective was to assess the differences in bone properties, using quantitative ultrasound (QUS, Sunlight Omnisensetrade mark, Sunlight Medical, Ltd., Tel Aviv, Israel), in male athletes involved in a weight-bearing, impact sport (soccer, SC) or a nonimpact sport (swimming and water polo, AQ), compared with nonathletic control (C) males. A total of 266 boys and men, aged 8 - 23 years, were divided into children (11.1 +/- 1.0 years; 34 SC, 34 AQ, 25 C), adolescents (14.7 +/- 1.2 years; 32 SC, 31 AQ, 31 C), and young adults (19.8 +/- 1.1 years; 31 SC, 24 AQ, 24 C) . Training experience varied between 1.5 years in the children to 15 years in the adults. Bone speed of sound (SOS) was measured bilaterally at the distal radius and the mid-tibia. Body fat was significantly lower in athletes compared with C. AQ were generally heavier and had a higher fat-free mass compared with SC and C, with no significant differences in height between groups. Radial SOS increased with age, but no differences were observed between activity groups or between the dominant (D) and nondominant (ND) arm. Tibial SOS also increased with age. In the children and adolescents, no differences were observed between activity groups. However, among adults, both SC and AQ had higher tibial SOS compared with C. These differences were mainly explained by differences in fat-free mass. Among young adults but not among children and adolescent males, both soccer and aquatic sports appear to be associated with higher bone SOS in the lower, but not the upper, extremities. Further studies are needed to assess possible sport-specific mechanisms which affect bone properties and to determine the minimal cumulative effect which is needed to influence bone properties.

The influence of game duration and playing position on intensity of exercise during match-play in elite water polo players.
J Sports Sci. 2006 Nov;24(11):1173-81.
Platanou T, Geladas N.
Department of Coaching in Aquatic Sports, Faculty of Physical Education and Sport Science, University of Athens, Athens, Greece.

In this study, we assessed exercise intensity in 20 water polo games of different duration. The hypothesis that right wing players perform at a higher intensity than back and forward central players was also tested. Thirty water polo players, equally split between three field positions, participated in the study. Initially, their performance-related physiological capabilities were evaluated. Subsequently, during water polo games of short (4 x 7-min periods) or long duration (4 x 9-min periods), heart rate was monitored continuously and blood lactate concentration was measured at the end of each period. Activity patterns were also recorded using a video camera. Mean heart rate over the entire game was 156 +/- 18 beats x min(-1). Overall exercise intensity fluctuated around a value corresponding to the lactate threshold (4.03 +/- 0.96 mmol x l(-1), 86 +/- 5% of peak heart rate) and decreased (P < 0.003) with game time (4.22 +/- 1.8 and 3.47 +/- 1.9 mmol x l(-1) in the second and fourth quarter, respectively). During the last 6 min, heart rate was higher (P < 0.001) in games of short duration (156 +/- 3 beats x min(-1)) than in games of long duration (152 +/- 8 beats x min(-1)). Video analysis showed that the percentage of time spent in low-intensity activities (i.e. "out of game") was lower (23 vs. 26%), whereas that in high-intensity activities (i.e. "sprinting crawl") was higher (21 vs. 19%), in games of short compared with long duration. No difference was observed among players of various field positions in any of the variables examined. Thus during match-play, games of long duration produced significantly lower heart rate responses than games of short duration, and the physiological response exhibited by the players was not affected by field position. The water polo authorities should consider these results before changing game duration and coaches should prepare their athletes accordingly.