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Assessing Energy Substrate Oxidation In Vitro with 14CO2 Trapping
Published on: March 23, 2022
Substrate metabolism and exercise performance with caffeine and carbohydrate intake
Carl J Hulston1, Asker E Jeukendrup
1School of Sport and Exercise Sciences, University of Birmingham, Birmingham, United Kingdom.
Combining caffeine with carbohydrates during exercise significantly improved cycling performance. However, caffeine did not affect carbohydrate oxidation or glucose metabolism during steady-state exercise.
Area of Science:
- Exercise Physiology
- Nutritional Science
- Sports Performance
Background:
- Carbohydrate (CHO) ingestion is a common strategy to fuel endurance exercise.
- Caffeine is known to enhance endurance performance, but its effect on CHO metabolism during exercise is less clear.
Purpose of the Study:
- To examine how caffeine affects exogenous carbohydrate oxidation and glucose kinetics during exercise.
- To determine if combining caffeine with carbohydrates improves cycling performance compared to carbohydrates alone.
Main Methods:
- Ten trained cyclists completed 105 minutes of steady-state cycling followed by a time trial.
- Participants ingested a glucose solution (GLU), a glucose plus caffeine solution (GLU + CAF), or a placebo (PLA).
- Isotopic tracers ([U-13C]glucose and [6,6-2H2]glucose) were used to measure glucose kinetics.
Main Results:
- Exogenous CHO oxidation rates and glucose kinetics (Ra and Rd) were similar between GLU and GLU + CAF trials.
- Cycling time trial performance was significantly improved with GLU + CAF (4.6% faster) compared to GLU alone.
- GLU + CAF also resulted in a 9% performance improvement compared to PLA.
Conclusions:
- Co-ingestion of caffeine (5.3 mg/kg) with CHO enhances cycling time trial performance.
- Caffeine does not alter exogenous CHO oxidation or glucose kinetics during steady-state exercise.
- The performance benefits of combined caffeine and CHO ingestion appear independent of altered carbohydrate metabolism.
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