How carb loading works
Muscle glycogen is the primary fuel for moderate-to-high intensity endurance exercise. Typical glycogen stores support 90–120 minutes of sustained effort. Carbohydrate loading (6–12 g/kg/day for 1–3 days) can increase glycogen stores by 20–40% above normal, effectively extending the duration before glycogen depletion becomes performance-limiting.
The final day of loading uses a reduced carbohydrate intake (typically 50% of the loading dose) and fewer meals to minimise gastrointestinal discomfort close to the event. High-fibre foods are progressively reduced in the final 24–48 hours for the same reason.