Abstract
879 The influence of glucose ingestion on fuel utilization during prolonged exercise in children and adolescents is currently unknown. We determined the percentage of total energy provision covered by exogenous glucose (GLUexo) ingestion during prolonged exercise, in boys ages 12-16. Healthy untrained volunteers exercised for 120 min at 60%VO2max on a cycle ergometer while ingesting either water or a 13C-enriched GLUexo beverage (∼3 g glucose/kg body mass). Total fat and carbohydrate utilization was determined from VO2 and respiratory exchange ratio and GLUexo oxidation was calculated from 13C/12C ratio in expired air. Carbohydrate utilization was 169.1 ± 12.9 g/120 min and 203.1 ± 15.9 g/120 min (P<0.01) and fat utilization was 31.0 ± 4.2 g/120 min and 17.1 ± 2.5 g/120 min (P<0.01) when subjects drank water and GLUexo, respectively. The total amount of GLUexo oxidized was 57.8 ± 4.3 g or 34.2 ± 2.2% of that ingested. Compared with water intake, GLUexo intake lowered endogenous glucose utilization from 169.1 ± 12.9 g/120 min to 145.3 ± 11.9 g/120 min (P<0.01). It also increased plasma insulin and whole blood glucose levels by 226% and 37%, respectively and lowered plasma free fatty acids and glycerol levels by 27% and 79%, respectively (all P<0.05). In conclusion, under these experimental conditions, GLUexo intake spares endogenous carbohydrate by 16% and contributes to approximately 25% of the total energy demand of exercise. Supported by, Gatorade Sports Science Institute
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