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Published on: October 17, 2018
Performance and metabolic responses to a high caffeine dose during prolonged exercise
1School of Human Biology, University of Guelph, Ontario, Canada.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|December 1, 1991
Summary
High caffeine doses significantly improved endurance performance in trained runners for both running and cycling. This enhancement was linked to increased epinephrine levels but did not alter key metabolic markers.
Area of Science:
- Exercise Physiology
- Sports Nutrition
- Human Performance
Background:
- Caffeine is a widely used ergogenic aid in sports.
- Its effects on substrate metabolism and performance in highly trained athletes require further investigation.
- Understanding caffeine's impact on endurance is crucial for optimizing athletic strategies.
Purpose of the Study:
- To determine if a high caffeine dose enhances running and cycling performance in well-trained athletes.
- To investigate the effects of caffeine on substrate metabolism during prolonged exercise.
- To analyze hormonal responses, specifically plasma epinephrine and norepinephrine, to caffeine ingestion.
Main Methods:
- Seven trained competitive runners participated in a randomized, double-blind, placebo-controlled study.
- Subjects completed four exercise trials (running and cycling to exhaustion) at approximately 85% VO2max.
- Caffeine (9 mg/kg) or placebo was ingested 1 hour before exercise; physiological and metabolic markers were measured.
Main Results:
- Caffeine significantly increased endurance times in both running (49.2 to 71.0 min) and cycling (39.2 to 59.3 min).
- Plasma epinephrine concentrations increased significantly with caffeine at rest, during exercise, and at exhaustion.
- Caffeine elevated plasma glycerol but had no significant effect on respiratory exchange ratio or free fatty acids.
Conclusions:
- A high dose of caffeine (9 mg/kg) effectively improves endurance performance in well-trained runners.
- The ergogenic effect of caffeine appears to be mediated, in part, by increased epinephrine levels.
- Caffeine influences glycerol metabolism but does not significantly alter carbohydrate or fat utilization during intense exercise.
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