This post is rated Olympians and Ironman.

If you’ve ever experienced one, you’ll never forget it. Hopefully, you’ve only experienced ONE…

On the other hand, if you are not familiar with this concept, watch this short video clip. (This is not for the weak of heart.)

Painful, isn’t it? So you might be asking yourself “why and how do this happen?” The term “Bonk” is synonymous with the phrase “Hitting the Wall.” Let’s look at the science behind the condition to gain further insight:

According to Wikipedia, a bonk is “a condition caused by the depletion of glycogen stores in the liver and muscles, which manifests itself by sudden fatigue and loss of energy.” The video clip you just watched is an extreme case, but no doubt a possibility. If you deplete your glycogen stores and fail to replenish at a rate sufficient to match your activity, your body will shut down and the result is a bonk.

Not only will a bonk end your training or racing day, but it also carries long term effects:

Cycling: exhaustion can reach the point where the cyclist is unable to stand without the support provided by the bike. Symptoms of depletion include general weakness, fatigue, and manifestations of hypoglycemia, such as dizziness and even hallucinations. This condition will not be relieved by brief periods of rest.

Running:  the brain’s production of dopamine (the neurotransmitter responsible for generating feelings of excitement, reward, motivation, and pleasure) begins to drop even as serotonin levels are rising,which can be the cause of the mental voices in your head telling you “I can’t do it.” So here you have a classic of “thinking problems.”

Anyway you see it, bonking or “hitting the wall” is a serious situation. Do not underestimate the stress that you are causing your body in your training. Keep up with your nutrition and always be mindful of your perceived level of exertion.