Hitting the wall

Hitting the wall is the sudden slump that often strikes between km 30 and 35 of a marathon: heavy legs, a collapsing pace, sometimes dizziness. The main cause: running out of glycogen, the carbohydrate stored in muscles and liver.

• These stores last about 90 minutes to 2 hours at marathon pace; starting too fast empties them sooner.
• Carb-load for the 2 to 3 days before.
• In the race, take 60 to 90 g of carbohydrate per hour from the first 30 to 45 minutes.
• Long runs of 30 to 35 km teach your body to burn more fat and store more glycogen.

If it hits: slow down, take carbohydrate and water, walk a minute. Confusion, chest pain or fainting: stop and get help at a first-aid post.