How to Avoid Hitting the Wall in a Marathon

Choose a pace supported by recent training and adjust for the course and weather. Avoid treating a calculator prediction as proof that you can sustain that pace for a marathon. A controlled start leaves room to reassess; it cannot guarantee a strong finish.

The Australian Institute of Sport lists 30–60 grams of carbohydrate per hour for endurance exercise lasting one to two-and-a-half hours, and up to 90 grams per hour for longer events using suitable mixed carbohydrate sources. These are general targets to practice and individualize, not a requirement to start at the upper limit.

Count carbohydrate from drinks and food as well as gels. For example, a practiced target of 40 grams per hour over four hours requires 160 grams. If gels supply all of it and each contains 20 grams, that is eight gels. There is no universal four-to-six-gel recommendation.

Carry or arrange access to fluids without forcing a fixed amount beyond your needs. Wilderness Medical Society guidance identifies overdrinking as a major cause of exercise-associated hyponatremia; electrolytes do not make excessive drinking safe.

Slow or stop and seek race medical support if symptoms are severe, unusual or not settling. Do not assume confusion, collapse or inability to continue is simply low fuel. In heat, confusion or loss of consciousness can indicate heat stroke and requires emergency help and rapid cooling. Finishing the race is secondary to getting help.