In England, bonking is slang for the act of copulation or coitus, which many people find to be a natural, zesty enterprise. In cycling, bonking is what happens when you run out of glycogen stores, haven’t ingested enough carbs to produce more blood glucose and are still riding the bike. It is less-than-zesty. In fact, its downright awful.
Here’s just one description I’ve found for bonking and, based on personal experience, it is right on the money:
When you bonk, physical exertion becomes extraordinarily difficult. Your muscles don’t have the fuel they need to operate effectively and forcing them to work becomes more and more difficult. You feel extremely weak and lethargic. You may tremble and shake uncontrollably and sweat profusely. You feel dizzy and light headed. Your sense of balance is upset. You may have heart palpitations. You will probably feel ravenously hungry.
On the mental and emotional side you will probably feel nervous and anxious. You may become confused and disoriented. You will have low emotional control and will become hostile, belligerent and easily irritated. You may experience overwhelming feelings of being defeated, hopeless and unable to go on. Your awareness of what’s going on around you will shrink and can arrive at an extreme form of tunnel vision in which the only thing you’re aware of is the spot on the road ahead that you’re staring at. You may have difficulty speaking. At the extreme, hypoglycemia can produce seizures and coma. In a word, it sucks.
The key to avoiding the bonk is making sure you eat and drink throughout any ride that lasts more than one hour. I recently found a good article from Portland’s CycleOne Coaching in the Harvest Century newsletter about eating for endurance. Definitely worth the read.