Bonking is the feeling of being out of gas, where your legs have turned to jelly, and the body is just not right with the world. If you were a runner it would be called “Hitting the Wall”. A doctor would say you had low blood sugar (read fuel). It also means you haven’t taken in enough carbohydrates and have exhausted your body’s glycogen stores, leaving you with abnormally low blood glucose levels. Your body can only store enough glucose (in the form of glycogen) to last you 90 minutes of moderate exercise. Once your glycogen is gone, your body will start using fat for fuel, which is released more slowly than a carbohydrate. That means you will be getting less power to your pedals!

So, what should you do if you feel a bonk coming on?

• First thing to do is to ingest some simple carbs that your body can quickly absorb so that your blood sugar level rises. These could be in the form of energy gels with plenty of water, a jam sandwich, sugar cubes, or jelly beans. (Energy bars are a complex carb and take much longer to absorb and convert to fuel.) 

• Prevention is key, so plan to ingest simple and complex carbs, use sports drinks, gels, bars and other portable snacks to replenish glycogen stores during your ride. This means ingesting about 150-250 calories of some form of high carbs every 30 minutes, even in the first hour of your ride. Whatever you choose to eat, the main thing is not to forget to eat. You may think you’d never forget to eat, but you might be surprised at how easy it is to forget on a long ride.

Our video is from our friends across the pond at GCN. This video times in at over 6 minutes, but it does go into more depth on longer ride planning and pacing strategies. It even has "Bonk Graphs" and a must-see pizza delivery mechanism at the 2:25 mark.