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Related Experiment Video

Updated: Jan 7, 2026

Evaluation of Blood Lactate and Plasma Insulin During High-intensity Exercise by Antecubital Vein Catheterization
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No Performance Effects of Altered Carbohydrate Distribution During Intense Cycling.

Tim Podlogar1,2,3, Blaž Grmek3,4, Luka Pungerčar5

  • 1Public Health and Sport Sciences, The Medical School, University of Exeter, Exeter, United Kingdom.

International Journal of Sport Nutrition and Exercise Metabolism
|December 30, 2025
PubMed
Summary

Carbohydrate intake timing during endurance cycling did not significantly impact performance. A decreasing intake pattern may improve fuel use and gut comfort later in exercise, though even intake is generally recommended.

Keywords:
carbohydratesexercise metabolismexercise performancesports nutrition

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Area of Science:

  • Sports Science and Exercise Physiology
  • Nutritional Biochemistry

Background:

  • Optimizing carbohydrate intake is crucial for endurance athletes.
  • Different ingestion patterns may influence fuel utilization and gastrointestinal comfort.

Purpose of the Study:

  • To investigate the effects of increasing, decreasing, and constant carbohydrate ingestion patterns on cycling performance and gastrointestinal comfort.
  • To test the hypothesis that aligning carbohydrate availability with endogenous stores optimizes outcomes.

Main Methods:

  • Twelve trained male cyclists completed three randomized trials.
  • Trials included a 180-min intermittent cycling preload, a 15-min all-out test, and a maximal sprint.
  • Participants ingested 90 g/hr of carbohydrates in increasing, decreasing, or constant patterns.

Main Results:

  • Carbohydrate distribution patterns did not significantly affect 15-min all-out performance or time to exhaustion.
  • Carbohydrate oxidation was higher with a decreasing pattern compared to constant or increasing patterns.
  • Gastrointestinal discomfort, including nausea and cramping, increased over time with an increasing pattern compared to a decreasing pattern.

Conclusions:

  • Carbohydrate intake distribution has minimal impact on overall endurance cycling performance.
  • A decreasing carbohydrate intake pattern may enhance substrate oxidation and gut comfort during prolonged exercise.
  • Even carbohydrate intake is generally advised, but uneven patterns might be acceptable depending on individual tolerance.