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Carbohydrate supplementation and perceived exertion during prolonged running
Alan C Utter1, Jie Kang, David C Nieman
1Department of Health, Leisure, and Exercise Science, Appalachian State University, Boone, NC, USA. utterac@appstate.edu
Medicine and Science in Sports and Exercise
|June 5, 2004
Summary
Carbohydrate supplementation during prolonged running lowers perceived exertion by increasing carbohydrate oxidation and altering hormone levels, even without changing muscle glycogen. This supports a link between fuel use, hormones, and exercise intensity perception.
Area of Science:
- Exercise Physiology
- Sports Nutrition
- Endocrinology
Background:
- Perception of exertion (RPE) significantly impacts endurance performance.
- Understanding the physiological factors influencing RPE during prolonged exercise is crucial for athletes.
- Carbohydrate availability and hormonal responses are hypothesized to play key roles in modulating RPE.
Purpose of the Study:
- To examine the relationship between carbohydrate energy substrate and hormonal regulation on perceived exertion during extended running.
- To determine if carbohydrate intake influences RPE through metabolic and hormonal pathways.
Main Methods:
- Sixteen experienced marathon runners completed a 3-hour treadmill run at 70% VO2max.
- Participants consumed either a carbohydrate (C) or placebo (P) beverage during exercise.
- Blood and muscle samples were analyzed for metabolic and hormonal markers pre- and post-exercise.
Main Results:
- Ratings of perceived exertion (RPE) were significantly lower with carbohydrate intake compared to placebo, especially later in the run.
- Carbohydrate ingestion increased respiratory exchange ratio and carbohydrate oxidation rates.
- Plasma glucose, insulin, and lactate were higher, while plasma cortisol was lower with carbohydrate supplementation.
- No significant difference in muscle glycogen content was observed between conditions.
Conclusions:
- Lower RPE during prolonged running is associated with increased carbohydrate oxidation, higher plasma glucose and insulin, and lower cortisol levels following carbohydrate supplementation.
- These findings suggest a physiological connection between carbohydrate availability, hormonal status, and the perception of effort in endurance exercise.
- Muscle glycogen content did not appear to be the primary mediator of the observed RPE changes.