EFFECTS OF HYPERHYDRATION ON TOTAL-BODY WATER, TEMPERATURE REGULATIONAND PERFORMANCE OF ELITE YOUNG SOCCER PLAYERS IN A WARM CLIMATE

The purpose of this study was to test the effect of increased fluid in take on temperature regulation and performance in elite soccer players . Eight players of the Puerto Rico National Team were studied under fi eld conditions at a Wet Bulb Globe Temperature (WBGT) heat stress inde x of 25.3 +/- 0.5 degrees C. They were young (17.0 +/- 0.6 yr) and wel l aerobically conditioned, as shown by their maximum aerobic power of 69.2 +/- 0.7 ml . kg(-1) min(-1). Players were randomly allocated to a week of voluntary hydration (VH) (fluid intake = 2.7 +/- 0.21 . day(- 1)) and a week of hyperhydration (HH) (fluid intake = 4.6 +/- 0.21 . d ay(-1)) (p < 0.05) prior to a soccer match. Their total body water (TB W) increased in HH compared to VH (p < 0.05), despite a significant in crease in urine output (p < 0.01). The soccer match was played at 82 /- 7% (VH) and 83 +/- 6% (HH) of maximum heart rate. Sweat losses and core temperature increases during the match were similar in both hydra tion conditions, When the environmental conditions were taken into con sideration, the increase in core temperature during the match rose, as a function of the heat stress index, only in VH (p < 0.05). Plasma vo lume was slightly reduced in both hydration conditions (ns). Performan ce assessment at the end of the soccer match revealed that average tim e to complete 7 repetitions of a soccer specific test was significantl y increased (p < 0.05) after the match in both hydration conditions bu t showed no difference between them. Peak torque a nd fatigability of knee flexor and extensor muscle groups at 240 deg . sec(-1), measured on a Cybex 340 dynamometer, were similar in both hydration conditions and not affected by the soccer match. The data suggest that additional water intake in these heat-acclimated players increased body water re serves and improved temperature regulation during a soccer match with no significant effect on the decrement in soccer specific performance observed at the end of a soccer match.