title: Voluntary fluid intake, hydration status, and aerobic performance of adolescent athletes in the heat.
abstract: We determined whether beverage flavoring and composition would stimulate voluntary drink intake, prevent dehydration, and maintain exercise performance in heat-acclimated adolescent males running in the heat. Eight adolescent (age, 13.7 ± 1.1 years) runners (peak oxygen uptake, 59.5 ± 4.0 mL·kg-1·min-1) underwent at least four 80-min exercise heat-acclimation sessions before completing 3 experimental sessions. All sessions were performed at 30 °C and 60%-65% relative humidity. Each experimental session consisted of five 15-min treadmill runs at a speed eliciting 65% peak oxygen uptake, with a 5 min rest prior to each run. Ten minutes after the final run, a time to exhaustion test was performed at a speed eliciting 90% peak oxygen uptake. Counterbalanced experimental sessions were identical, except for fluid intake, which consisted of tap water (W), flavored water (FW), and FW with 6% carbohydrate and 18 mmol·L-1 NaCl (CNa) consumed ad libitum. Fluid intake and body weight were monitored to calculate dehydration. Voluntary fluid intake was similar to fluid losses in W (1032 ± 130 vs. 1340 ± 246 g), FW (1086 ± 86 vs. 1451 ± 253 g), and CNa (1259 ± 119 vs. 1358 ± 234 g). As a result, significant dehydration was avoided in all trials (-0.45% ± 0.68% body weight in W, -0.66% ± 0.50% body weight in FW, and -0.13% ± 0.71% body weight in CNa). Core temperature increased by ~1 °C during exercise, but was not different between trials. Time to exhaustion was not different between trials and averaged 8.8 ± 1.7 min. Under exercise conditions more closely reflecting real-life situations, heat-acclimatized adolescent male runners can appropriately gauge fluid intake regardless of the type of beverage made available, resulting in consistency in exercise performance.
authors.affiliation: Children's Exercise and Nutrition Centre, McMaster University, Hamilton, ON L8N 3Z5, Canada.
authors.forename: Boguslaw
authors.initials: B
authors.lastname: Wilk
authors.forename: Brian W
authors.initials: BW
authors.lastname: Timmons
authors.forename: Oded
authors.initials: O
authors.lastname: Bar-Or
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D056352:Athletes; D054874:Athletic Performance / Q000502:physiology*; D001628:Beverages / Q000032:analysis; D001835:Body Weight; D002648:Child; D002652:Child Behavior; D018592:Cross-Over Studies; D003681:Dehydration / Q000517:prevention & control*; D004326:Drinking; D005518:Food Preferences; D006358:Hot Temperature; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology; D012420:Running; D013997:Time Factors