Glycogen is glucose stored in muscle (approximately 400-500g in trained athletes) and liver (100-120g). It’s the primary fuel for exercise above 65-70% of VO2 max — the fuel for all high-intensity efforts. Glycogen depletion causes the ‘bonk’ or hitting the wall in endurance events. Replenishment requires carbohydrate intake — consuming 1-1.2g/kg carbohydrate per hour in the first 4 hours post-exercise maximises glycogen restoration. Low-carbohydrate diets reduce glycogen stores and directly impair high-intensity performance, though they may be appropriate for low-intensity fat-adaptation training.
Key points
- 400-500g stored in trained muscle
- Primary fuel above 65-70% VO2 max
- Depletion = ‘bonk’ / hitting the wall
- 1-1.2g/kg/hr carbs post-exercise for rapid replenishment