Bonking / Hitting the Wall

Sudden depletion of glycogen stores mid-race causing near-total energy collapse.

The 'wall' or 'bonk' describes the sudden onset of heavy legs and near-zero energy when the body has burned through all available glycogen. In long-distance triathlon it typically strikes on the run between km 25 and km 35. Its severity depends directly on fueling strategy and bike pacing : going too hard on the bike depletes stores before the run. Prevention: regular gel intake from the first minutes on the bike, before hunger strikes.