I heard some people say it few times - "He hit the wall and couldn't finish the race...". What does it mean? what happens to the body in this situation? How can this be avoided?

  • 1
    I've seen some very colorful language applied to this - "the piano effect" (suddenly feels like you're carrying a piano) or "the fridge" (as in, "I was doing fine until the guy handed me a fridge in mile 23!")
    – pjmorse
    May 11, 2013 at 0:58

1 Answer 1


Wikipedia's definition:

In endurance sports such as 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 sudden fatigue and loss of energy.

Hitting the wall means sudden fatigue and loss of energy which is caused by the depletion of glycogen stores in the liver and muscles.

In this situation, your body feel general weakness, fatigue, and manifestations of hypoglycemia, such as dizziness and even hallucinations.

To avoid this you need to

  • ensure the glycogen levels are high when the running begins
  • maintain glucose levels during running by eating or drinking carbohydrate-rich substances, or by reducing running intensity.
  • 3
    Add to that diligent training, and you've got your perfect answer of how to avoid "the wall". When you train, you don't only build muscle, but also train the body in energy transfer. May 2, 2013 at 11:27
  • 3
    Adequate training can help, but even a well trained athlete can still "hit the wall" so it's not a guaranteed answer to the problem - the excitement of the race or desire for a particular finishing time may lead them to run faster than normal. Or they may not hydrate or eat adequately ("There's too many people at that water stop, the next one is only 2 miles away"), etc. Weather can also contribute to the problem, i.e. you did your training at home in 60 degree weather and it's 85 degrees on race day.
    – Johnny
    May 3, 2013 at 21:41
  • Johnny's right - it's not at all uncommon to see highly-trained professionals bonking after a too-ambitious start. To really do your best in a marathon you have to get right up to the edge of a bonk, but not go over. It's a tricky balance.
    – pjmorse
    May 11, 2013 at 0:56
  • How can you ensure the high levels of glycogen? Can the hitting the wall be also the result of dehydration?
    – hhh
    Jun 11, 2013 at 23:48

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