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No placebo effect from carbohydrate intake during prolonged exercise
Carl J Hulston1, Asker E Jeukendrup
1School of Sport and Exercise Sciences, University of Birmingham, Birmingham, UK.
Carbohydrate intake significantly improved cycling performance, contrary to a placebo effect. Participants believed they consumed carbohydrates, but only the actual carbohydrate-electrolyte solution enhanced performance.
Area of Science:
- Sports Science
- Exercise Physiology
- Nutritional Science
Background:
- Carbohydrate (CHO) intake is known to enhance endurance performance.
- The potential for a placebo effect from perceived CHO intake requires further investigation.
Purpose of the Study:
- To investigate the placebo effect of carbohydrate intake during prolonged exercise.
- To compare the performance effects of water, a placebo drink, and a carbohydrate-electrolyte solution.
Main Methods:
- Ten endurance-trained male cyclists completed three 120-minute cycling trials at 61% VO2max.
- Participants ingested plain water (WAT), a placebo (PLA) with identical taste/color to CES, or a 6% carbohydrate-electrolyte solution (CES).
- Participants were misinformed that both flavored solutions contained carbohydrates.
Main Results:
- Carbohydrate-electrolyte solution (CES) ingestion enhanced time trial (TT) performance by 11.3% compared to water (p < .05).
- CES improved TT performance by 10.6% compared to the placebo (p < .05).
- No significant performance difference was observed between the placebo (PLA) and water (WAT) trials.
Conclusions:
- No placebo effect was observed when participants believed they consumed carbohydrates.
- Actual carbohydrate intake via a carbohydrate-electrolyte solution significantly improved cycling performance.
- The study highlights the ergogenic benefits of carbohydrate-electrolyte solutions during prolonged endurance exercise.
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