How the body uses energy from carbohydrate loading differs from regular carbohydrate intake during long exercise

Muscle glycogen levels were 194 +/- 4 mmol/kg in carbohydrate-loaded cyclists and 124 +/- 8 mmol/kg in those who ingested a carbohydrate drink without prior loading.

• Total carbohydrate oxidation was similar between both groups during exercise.
• Cyclists who ingested the carbohydrate drink showed higher rates of glucose appearance and oxidation compared to those who were carbohydrate-loaded.
• Endogenous glucose appearance and oxidation were significantly lower in cyclists without prior carbohydrate loading.
• Muscle glycogen levels decreased at the same rate in the first hour for both groups but declined more rapidly in those without carbohydrate loading thereafter.
• Carbohydrate loading before exercise may reduce the contribution of plasma glucose oxidation to overall carbohydrate oxidation while prolonging time to exhaustion.

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