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Exogenous glucose oxidation during exercise in relation to the power output
F Pirnay1, A J Scheen, J F Gautier
1Department of Medicine, University of Liege, Belgium.
International Journal of Sports Medicine
|October 1, 1995
Summary
This study shows that during exercise, the body oxidizes ingested glucose, with the rate increasing at moderate intensity but plateauing or decreasing at high intensity. Glucose oxidation significantly contributes to energy needs, especially at higher exercise levels.
Area of Science:
- Exercise Physiology
- Human Metabolism
- Nutritional Biochemistry
Background:
- Understanding substrate utilization during exercise is crucial for optimizing athletic performance and nutritional strategies.
- The role of exogenous glucose in meeting energy demands during varying exercise intensities requires further elucidation.
Purpose of the Study:
- To investigate the impact of exercise power output on the oxidation rate of ingested 13C-labeled glucose.
- To determine the contribution of exogenous glucose and other substrates to total energy expenditure during graded exercise.
Main Methods:
- Combines indirect calorimetry with stable isotope tracer techniques (13C-glucose).
- Subjects performed graded uphill treadmill exercise at 45%, 60%, and 75% of maximal oxygen consumption (VO2max).
- Ingested 100g of 13C-labeled glucose and measurements taken over several hours.
Main Results:
- Exogenous glucose oxidation increased with exercise intensity up to 60% VO2max, then plateaued or decreased at 75% VO2max.
- The contribution of exogenous glucose to total energy supply decreased as exercise intensity rose (19.6% to 12.2%).
- Carbohydrate contribution to energy increased with intensity, while lipid contribution decreased.
Conclusions:
- Ingested exogenous glucose is significantly oxidized during exercise and contributes substantially to energy supply.
- The oxidation rate of exogenous glucose is intensity-dependent, peaking at moderate exercise levels.
- Higher exercise intensities shift substrate utilization towards endogenous and exogenous carbohydrates.