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Oxidation of [13C]glucose ingested before and/or during prolonged exercise.
Anny Caron1, Carole Lavoie, François Péronnet
1Département des sciences de l'activité physique, Université du Québec à Trois Rivières, CP 500, G9A 5H7, Trois Rivières, Quebec, Canada.
European Journal of Applied Physiology
|October 21, 2003
Summary
Ingesting glucose before exercise does not boost how quickly your body uses glucose during exercise. However, consuming glucose both before and during exercise increases the total amount of glucose your body oxidizes.
Area of Science:
- Exercise Physiology
- Nutritional Science
- Metabolic Studies
Background:
- Ingesting glucose before exercise transiently elevates plasma insulin.
- Elevated insulin may potentially enhance exogenous glucose oxidation during exercise.
- Understanding optimal glucose timing for fuel utilization during exercise is crucial for performance.
Purpose of the Study:
- To investigate if ingesting glucose before exercise enhances exogenous glucose oxidation during exercise.
- To determine the effect of pre-exercise glucose ingestion on insulin and glucose kinetics during exercise.
- To compare exogenous glucose oxidation rates when glucose is consumed before and/or during exercise.
Main Methods:
- Six young male subjects participated in a controlled exercise protocol.
- Subjects ingested 50g of glucose 30 minutes before exercise and/or 110-160g during exercise.
- Carbon-13 (¹³C) labeling was used to trace the oxidation of exogenous glucose during 120 minutes of exercise at 67.3% maximal oxygen uptake.
Main Results:
- Pre-exercise glucose ingestion significantly increased plasma insulin but returned to baseline within 30 minutes of exercise onset.
- Exogenous glucose oxidation was not enhanced in the initial 30-60 minutes of exercise with pre-exercise glucose.
- Total exogenous glucose oxidized was higher when consumed both before and during exercise (65.7g) compared to during exercise only (49.2g).
Conclusions:
- Ingesting glucose 30 minutes prior to exercise does not improve the rate of exogenous glucose oxidation during the exercise bout.
- Consuming glucose both before and during exercise leads to a greater total oxidation of exogenous glucose compared to consuming it only during exercise.
- The findings suggest that while pre-exercise glucose doesn't accelerate oxidation, it contributes to a larger overall fuel supply utilized during prolonged exercise.