Introduction The goalkeeper is the most important defense player and is very important in team sports. The outcome of team games depends on a great extend on his performance. While there is a number of studies that have dealt with the physiological demands of the other players in the water polo game, the information for the physiological demands of the goalkeepers is limited to two studies on kinematics analysis (Smith 1998, Platanou 2002) and in one study measuring lactic acid in the end of the periods (Rodriguez 1994). The purpose of this study was to examine the physiological demands of the goalkeepers during the game. We additionally investigated whether there were significant differences in the intensity of the game between the periods. Methods For the duration of 8 official games heart rate was continuously monitored in 8 water polo goalkeepers participating in the First Greek National Division Championship. In addition capillary blood samples were collected at the end of each period, for lactate concentration determination. Before each game, the maximum heart rate (HRmax) was determined during maximal performance in the vertical position by adding weights until the point of exhaustion. For each player three different percentages (85%, 90% and 95%) of maximal heart rate were determined. This procedure permitted the measurements of the percentage of the game played above the respective sub - peak HR thresholds (viz. 85, 90 and 95% of HRmax) and above HRmax. ONE WAY ANOVA was used to compare the heart rate and the blood lactate between the periods. Results The mean (±SD) values of maximum heart rate for all players was 184.4±2.7. In addition, the mean (±SD) values corresponding to 85, 90, and 95% of maximal heart rate were 156.7±2.2, 166±2.3 and 175.4±2.7 beats/min respectively. The average heart rate of the goalkeepers during the games was 134.3±20.3 and the average heart rate at the intermissions was 125.5±24.6. Mean blood lactate accumulation after each period of the games was 3.93±1.64. Percentages of time spent at various exercise intensities during the games are shown on table 1. Discussion / Conclusions In conclusion, based on the results it appears that the predominant mechanism that supplies the goalkeepers´ performance, is the aerobic energy production system. This is evidenced by the low mean heart rate, the low mean blood lactate and the high percentage (91.21%) of the time that the goalkeepers performed, with intensities lower than 85% of maximum heart rate during the game. The intensity of the goalkeepers´ performance remains the same during the game and is not influenced by time passage as was evidenced in water polo players (Geladas 2000; Pinnington 1988).
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