Last updated: 3 October 2026
Reviewed by Jordan Morley, FA Level 2 Football Coach
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.
- 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
In practice
The body's glycogen stores (roughly 400-500g in muscle and liver combined for most adults) can be fully depleted by a hard, long training session, and restocking them efficiently afterward — ideally with a carbohydrate-rich meal within a few hours — helps ensure the next day's training isn't compromised by starting with already-low fuel reserves.
FAQ
How quickly should I eat carbs after a hard training session?
While the old '30-minute window' is now seen as less strict than once believed, eating a carbohydrate-containing meal within a few hours post-exercise supports efficient glycogen restocking, especially before back-to-back training days.
How much carbohydrate is needed to fully restock glycogen?
Roughly 5-10g of carbohydrate per kg of bodyweight over the 24 hours following a depleting session is a common guideline for athletes training again within a day.