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Exogenous carbohydrate oxidation from drinks ingested during prolonged exercise in a cold environment in humans
S D Galloway1, S A Wootton, J L Murphy
1Department of Biomedical Sciences, University Medical School, Foresterhill, Aberdeen AB25 2ZD, Scotland. s.d.r.galloway@stir.ac.uk
Journal of Applied Physiology (Bethesda, Md. : 1985)
|July 18, 2001
Summary
Ingesting glucose-electrolyte drinks during exercise in the cold did not alter exercise capacity. Exogenous glucose oxidation was similar to warmer conditions, suggesting it doesn't limit drink effectiveness in the cold.
Area of Science:
- Exercise Physiology
- Sports Nutrition
- Environmental Physiology
Background:
- Carbohydrate-electrolyte drinks are commonly used to enhance endurance exercise performance.
- The impact of cold environments on exogenous glucose oxidation and its effect on exercise capacity is not fully understood.
- Previous research suggests substrate oxidation may differ in varying environmental conditions.
Purpose of the Study:
- To investigate the effect of different glucose concentrations in carbohydrate-electrolyte beverages on exogenous glucose oxidation during prolonged exercise in a cold environment.
- To determine if exogenous glucose oxidation in the cold is comparable to that observed in temperate conditions.
- To assess the relationship between exogenous glucose oxidation and exercise capacity in a cold setting.
Main Methods:
- Six healthy males completed four exhaustive cycle ergometer rides at 80% maximal oxygen consumption in a cold environment.
- Subjects consumed a bolus and intermittent small volumes of fluid containing either a flavored water control or glucose-electrolyte beverages (2%, 6%, 12% [U-(13)C]glucose).
- Exogenous glucose oxidation was measured using stable isotope tracers, and exercise capacity was determined by time to exhaustion.
Main Results:
- Exercise capacity did not significantly differ across the four beverage trials (water, 2%, 6%, 12% glucose).
- Exogenous glucose oxidation was significantly lower in the 2% glucose trial compared to the 6% and 12% trials.
- Oxidation rates of exogenous glucose in the 6% and 12% trials were similar to those reported in warmer conditions.
- No significant differences in endogenous glucose oxidation were observed between trials.
Conclusions:
- The oxidation of exogenous glucose during prolonged exercise in the cold is comparable to that in warmer environments.
- The effectiveness of carbohydrate-electrolyte drinks for enhancing exercise capacity in the cold is unlikely to be limited by low exogenous glucose oxidation.
- These findings support the use of carbohydrate-electrolyte beverages for endurance exercise performance, even in cold conditions.