Drink composition, voluntary drinking, and fluid balance in exercising, trained, heat-acclimatized boys.
This study examined the effects of beverage composition on the voluntary drinking pattern, body fluid balance, and thermoregulation of heat-acclimatized trained boys exercising intermittently in outdoor conditions (wet bulb globe temperature 30.4 +/- 1.0 degreesC). Twelve boys (age 13.4 +/- 0.4 yr) performed two 3-h sessions, each consisting of four 20-min cycling bouts at 60% maximal aerobic power alternating with 25-min rest. One of two beverages was assigned: unflavored water (W) or flavored water plus 6% carbohydrate and 18 mmol/l Na (CNa). Drinking was ad libitum. Total intake was higher (P < 0.05) during CNa (1,943 +/- 190 g) compared with W (1,470 +/- 143 g). Euhydration was maintained with CNa (+0.18% body wt), but a mild dehydration resulted with W (-0.94% body wt; P < 0.05). Sweat loss, much higher than previously published for children of similar age, was similar between conditions (CNa = 1,644.7 +/- 117.5; W = 1,750.2 +/- 152.7 g). The increase in rectal temperature (CNa = 0.86 +/- 0.3; W = 0.76 +/- 0.1 degreesC), heart rate, and all perceptual variables did not differ between conditions. In conclusion, a flavored carbohydrate-electrolyte drink prevents voluntary dehydration in trained heat-acclimatized boys exercising in a tropical climate despite their large sweat losses. Because hydration changes were minor, the thermoregulatory strain observed was similar between conditions.
Rivera-Brown
A M
AM
Department of Physical Medicine, Rehabilitation and Sports Medicine, Center for Sports Health and Exercise Sciences at the Albergue Olímpico, University of Puerto Rico School of Medicine, Salinas, Puerto Rico 00751, USA.anriver@coqui.net
Gutiérrez
R
R
Gutiérrez
J C
JC
Frontera
W R
WR
Bar-Or
O
O
D000064:Acclimatization / Q000502:physiology*; D000293:Adolescent; D001833:Body Temperature Regulation / Q000502:physiology*; D002648:Child; D004326:Drinking / Q000502:physiology*; D015444:Exercise / Q000502:physiology; D005421:Flavoring Agents; D006358:Hot Temperature; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D010809:Physical Fitness / Q000502:physiology*; D013312:Stress, Physiological / Q000503:physiopathology; D014882:Water-Electrolyte Balance / Q000502:physiology*
D005421:Flavoring Agents