INVOLUNTARY DEHYDRATION IN CHILDREN AND ADOLESCENTS FOLLOWING A TRIATHLON RACE IN A HOT CLIMATE

Abstract

For ethical reasons, laboratory-based studies of dehydration in exercising children have not exceeded hypohydration levels of 1–1.5% body weight (BW). The purpose of this study was to determine whether this ceiling is justified, based on “real life” sports events. Ninety-two (84% of all participants) 8- to 17-year-old girls and boys were tested before and immediately following the Costa Rica National Triathlon Championship. Climatic conditions during the junior race (ages 8–13; 500 m swimming, 15 km cycling, 3.5 km running) were: 34–35°C dry bulb, 44–48% relative humidity and 30–32°C WBGT. Respective conditions in the senior race (ages 14–17; 800 m swimming, 30 km cycling, 8 km running) were 39–40°C, 30–38% and 31.5–32.5°C. Fluid intake was not controlled, nor were the subjects instructed to modify any of their behaviors before or during the race. Changes in hydration status were calculated from pre- and post-race naked (after voiding) BW. 50% of the boys and 48.1% girls in the junior group, and 34.5% boys and 20% girls in the senior goup lost 1–2% of initial BW. 15.4% boys and 14.8% girls in the junior group, and 31% boys and 20% girls in the senior group lost 2–3% BW. 6.9% of the senior boys lost more than 3% of BW. 73% of all subjects produced little (less than 40 ml) or no urine following the race. The degree of hypohydration could not be explained by the acclimatization status (based on the prevailing climate in their place of residence). There was a positive association between racing time and BW change in the junior boys (r = 0.41) and girls (r = 0.46) and in the senior boys (r = 0.38), but not in the senior girls (r = −0.20). We conclude that the levels of hypohydration under the above conditions markedly exceed those previously described in laboratory-based studies. Supported by Gatorade Sports Science Institute