title: Voluntary drinking and hydration in trained, heat-acclimatized girls exercising in a hot and humid climate.
abstract: This study examined the effects of beverage composition on the voluntary drinking pattern, body fluid balance and body temperature responses of heat-acclimatized trained girls exercising intermittently in outdoor conditions (WBGT = 30.9 +/- 0.2 degrees C). Twelve trained, heat-acclimatized girls (age = 10.6 +/- 0.2 years) performed three 3-h sessions, each consisting of four 20-min cycling bouts at 60% VO2max, alternating with 25-min rest. One of three beverages was assigned: unflavored water (W), flavored water (FW) or flavored water plus 6% carbohydrate and 18 mmol/l NaCl (CNa). Drinking was ad libitum. Total intake was similar among conditions (W = 953.3 +/- 107.8 ; FW = 1026.5 +/- 138.1; CNa = 906.4 +/- 107.5 g). A mild hypohydration occurred during the three conditions (W = -1.12%; FW = -0.95%; CNa = -0.74% BW, P > 0.05). Sweat loss, higher than previously reported for sedentary girls, was not different among conditions (W = 1,051.5 +/- 90.8; FW = 979.9 +/- 72.8; CNa = 1,052.7 +/- 52.6 g). The average amount of urine produced (W = 269.8 +/- 85.9; FW = 320.8 +/- 87.2; CNa = 85.6 +/- 9.3 g) was 73 and 68% lower [corrected] during CNa compared to [corrected] FW and W, respectively, [corrected] (CNa vs. FW, P < 0.05), CNa vs W, P = 0.06) [corrected] The increase in rectal temperature, heart rate and all perceptual variables did not differ among conditions. In conclusion, flavoring of the water and addition of 6% carbohydrate plus 18 mmol/l NaCl do not prevent mild hypohydration in trained, heat-acclimatized girls with high sweating rates. However, there is a tendency towards a greater fluid retention with the CNa beverage.
authors.affiliation: Center for Sports Health and Exercise Sciences at the Albergue Olímpico, Department of Physical Medicine, Rehabilitation and Sports Medicine, University of Puerto Rico School of Medicine, PO Box 2004, Salinas, Puerto Rico 00751. aniriver@coqui.net
authors.forename: Anita M
authors.initials: AM
authors.lastname: Rivera-Brown
authors.forename: Farah A
authors.initials: FA
authors.lastname: Ramírez-Marrero
authors.forename: Boguslaw
authors.initials: B
authors.lastname: Wilk
authors.forename: Oded
authors.initials: O
authors.lastname: Bar-Or
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D001831:Body Temperature / Q000502:physiology; D050260:Carbohydrate Metabolism / Q000502:physiology; D002648:Child; D003681:Dehydration / Q000503:physiopathology / Q000517:prevention & control*; D004327:Drinking Behavior / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006358:Hot Temperature; D006801:Humans; D010101:Oxygen Consumption / Q000502:physiology; D012965:Sodium Chloride / Q000378:metabolism; D013546:Sweating / Q000502:physiology; D014329:Tropical Climate; D014882:Water-Electrolyte Balance / Q000502:physiology
chemical_list: D012965:Sodium Chloride