Exogenous carbohydrate oxidation from drinks ingested during prolonged exercise in a cold environment in humans

• Published in: Journal of applied physiology (1985) 2001-08, Vol.91 (2), p.654-660
• Main Authors: Galloway, Stuart D. R, Wootton, Steve A, Murphy, Jane L, Maughan, Ronald J
• Format: Article
• Language: English
• Subjects: Acclimatization - physiology; Adult; Analysis of Variance; Beverages; Biological and medical sciences; Blood Glucose - metabolism; Carbohydrates; Carbon Isotopes; Cold Temperature; Dietary Carbohydrates; Electrolytes; Energy Metabolism; Exercise; Exercise - physiology; Fundamental and applied biological sciences. Psychology; Glucose; Humans; Isotopes; Lactates - blood; Male; Metabolisms and neurohumoral controls; Oxidation; Oxygen Consumption; Physical Exertion - physiology; Reference Values; Temperature; Time Factors; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/jappl.2001.91.2.654

1  Department of Biomedical Sciences, University Medical School, Foresterhill, Aberdeen AB25 2ZD, Scotland; and 2  Institute of Human Nutrition, University of Southampton, Southampton SO16 6YD, England, United Kingdom Six healthy male volunteers performed four rides to exhaustion on a cycle ergometer at ~80% of maximal oxygen consumption. Subjects ingested a bolus volume of fluid (7.14 ml/kg) immediately before exercise and additional fluid volumes (1.43 ml/kg) every 10 min during exercise. The fluids ingested were either a flavored water control or glucose-electrolyte beverages with glucose concentrations of 2, 6, or 12%. The beverages were labeled with [U- 13 C]glucose (99.2%: 0.05 g/l). Exercise capacity was not different ( P  = 0.13) between trials; median (range) exercise time was 83.52   (79.85-89.68), 103.19 (78.82-108.22), 100.37 (80.60-124.07), and 94.76 (76.78-114.25) min in the 0, 2, 6, and 12% trials, respectively. The oxidation of exogenous glucose in each 15-min period was significantly lower in the 2% trial ( P  = 0.02) than in the 6 and 12% trials where oxidation rates were between 0.5 and 0.7 g/min. No difference in endogenous glucose oxidation was observed between trials ( P   = 0.71). These findings indicate that the oxidation of exogenous glucose during exercise of this intensity and duration in a cold environment is similar to that observed in warmer conditions. Thus a low oxidation of exogenous substrate is unlikely to be a factor limiting the effectiveness of carbohydrate-electrolyte drink ingestion on exercise capacity in a cold environment. stable isotopes; hydration; glucose oxidation