Voluntary drinking and hydration in non-acclimatized girls exercising in the heat

The intent of this study was to assess the influence of drink flavor and composition on voluntary drinking and hydration status in girls exercising intermittently in the heat (35 ± 1°C, 45–50% relative humidity). Twelve physically active, nonacclimatized girls (9–12 years) performed three 3 h identical sessions, each consisting of four 20 min cycling bouts at 50% \( (\ifmmode\expandafter\dot\else\expandafter\.\fi{V}{\text{O}}_{{{\text{2}}\max }} ), \) separated by 25 min of rest. One of the three beverages (chilled to 8–10°C) was assigned to each session: unflavored water (W), grape-flavored water (FW) and grape-flavored water plus 6% carbohydrate and 18 mmol l⁻¹ NaCl (CNa). Drinking was ad libitum. Body weight (BW), drink intake (DI), heart rate, rectal and skin temperatures, and perceptions of thirst and stomach fullness were monitored periodically. Total DI was 759, 940, 1,045 g in W, FW and CNa, respectively (P < 0.05 for CNa–W and FW–W). BW changes were −0.15, 0.16, and 0.45% in W, FW and CNa, respectively, but only the difference between CNa and W was significant (P < 0.05). Other physiological and perceptual variables were not different between trials. In conclusion, beverage flavoring regardless if its combination with carbohydrate and NaCl, mildly enhanced voluntary drinking in young non-acclimatized girls. In contrast to previous research in young boys, euhydration was maintained in the girls by an adequate intake of unflavored water.