EFFECTS OF DIFFERENT CARBOHYDRATE-ELECTROLYTE BEVERAGES ON THE APPEARANCE OF INGESTED DEUTERIUM IN BODY-FLUIDS DURING MODERATE EXERCISE BY HUMANS IN THE HEAT

To determine whether different forms of glucose (free and polymer) ass ociated with sodium chloride influence the rate of water absorption du ring exercise in the heat, six men took part in five trials. Each tria l included a passive heating session which resulted in a 2% loss of bo dy mass, followed by Ih of treadmill exercise (at 50% of maximal oxyge n uptake) in warm conditions (dry bulb temperature 35 degrees C, relat ive humidity 20%-30%). Immediately before exercise, the subjects were given either no fluid or a volume equal to 50% of the fluid previously lost (about 650 mi), chosen from among four D2O-labelled beverages : mineral water, a 6% glucose-electrolyte solution (GS), a 6% maltodextr in solution and a 6% maltodextrin-electrolyte solution. No significant differences were observed among these various beverages so far as tem poral accumulation of deuterium in plasma, sweat and urine was concern ed. During GS, the plasma volume was completely restored and the drift s of heart rate and rectal temperature were less marked than during ot her trials. These results would suggest that rehydration with GS was m ore efficient, probably because of an internal redistribution of water . The proportion of ingested water was twice as high in sweat as it wa s in urine. These findings may reflect the essential part played by ci rculatory adjustments in the transfer of plasma water into sweat and u rine.