CONSISTENCY IN PREVENTING VOLUNTARY DEHYDRATION IN BOYS WHO DRINK A FLAVORED CARBOHYDRATE-NACL BEVERAGE DURING EXERCISE IN THE HEAT

Twelve 10- to 12-year-old healthy boys performed six 70-min intermitte nt exercise sessions (three 20-min cycling bouts at 50% (V) over dot O -2 max with 5 min rest in between) over a 2-week period at 35 +/- 1 de grees C, 50 +/- 5% or 60 +/- 5% relative humidity. Subjects drank grap e-flavored solution with 6% carbohydrate (2% glucose, 4% sucrose) and 18.0 mmol.L-1 NaCl ad libitum. Body weight (BW), heart rate, rectal te mperature, thirst, and stomach fullness perception were monitored peri odically. There were no differences among the six sessions in voluntar y drink intake (765-902 g), hydration level (+0.75 to +1.07 %BW), swea ting rate (245-263 g.m(-2).hr(-1)), and the other physiological and pe rceptual variables. A positive fluid balance was achieved in 67 out of 72 sessions. Voluntary drink intake of grape-flavored carbohydrate-Na Cl beverage was consistently sufficient to prevent dehydration in 10- to 12-year-old boys during repeated exposures of exercise in the heat. This effect is likely to be achieved through a combination of physiol ogical and behavioral mechanisms.