Bonking

In endurance sports, particularly cycling and running, hitting the wall or the bonk describes a condition caused by the depletion of glycogen stores in the liver and muscles, which manifests itself by precipitous fatigue and loss of energy. Milder instances can be remedied by brief rest and the ingestion of food or drinks containing carbohydrates. The condition can usually be avoided by ensuring that glycogen levels are high when the exercise begins, maintaining glycogen levels during exercise by eating or drinking carbohydrate-rich substances, or by reducing exercise intensity.