The Carbohydrate Revolution in the World of Endurance

A profound transformation is underway in endurance sports: high carbohydrate intake during training and competition has evolved from a practice reserved for elites to a strategy adopted by almost all serious athletes across all sports (running, trail running, cycling, triathlon).

Science is clear on this: increasing carbohydrate intake during exercise (30 to 120 g/h depending on duration and intensity) helps improve performance.

The study "A step towards personalized sports nutrition: carbohydrate intake during exercise" published in Sports Medicine is a major synthesis compiling accumulated knowledge on carbohydrate ingestion during endurance exercise. Jeukendrup, one of the world's most renowned researchers in this field, explains how to personalize carbohydrate intake based on duration, intensity, and type of effort to optimize performance.

 

Key Highlights

• Carbohydrates during exercise improve performance. For any prolonged effort (>60–90 minutes), consuming carbohydrates delays fatigue and increases the ability to maintain high intensity. Typical gains:
  10 to 30% additional time until exhaustion on efforts of 1 to 3 hours
  2 to 10% more average power in 30 to 60-minute time trials (even with full glycogen stores at the start)

 

Mechanisms of Action

• Maintenance of blood glucose levels (blood sugar) → prevents hypoglycemia and central fatigue
• Increased oxidation of ingested (exogenous) carbohydrates → spares muscle glycogen
• Reduction in energy cost (improved running/cycling economy)

 

Recommended Doses According to Effort Duration

• <45–60 min: not necessary (or very low dose if feeling a dip)
• 60–120 min: 30–60 g/h (glucose alone or mixture)
• 120–180 min: 60–90 g/h (ideally with 2:1 glucose:fructose ratio for better absorption)
• 180 min (ultras, Ironman): up to 90–120 g/h (mandatory gut training)

 

Importance of Glucose:Fructose Ratio: Glucose alone is limited to ~60 g/h absorption. Adding fructose (2:1 or 1:0.8 ratio) allows reaching 90 g/h+ without overloading the gut, thanks to different transporters.

 

Personalization: Gastrointestinal tolerance varies enormously from athlete to athlete → it's essential to test and train the gut (just like training legs). Some tolerate 120 g/h without issues, others experience problems at 60 g/h.

 

 

Study Conclusion:

Strategic carbohydrate consumption during exercise is one of the most powerful and scientifically proven tools for improving endurance performance. By personalizing the dose and type (glucose:fructose ratio), physical limits can be significantly pushed, even in highly trained athletes.