To bonk is to

completely exhaust all your bodies stores of glycogen

Glycogen is the bodies way of storing carbohydrates in an easy to release form for your muscles to use. Carbohydrates are converted into glycogen and stored in the liver and within the muscles. This is a limited ammount of energy that is the cyclist primary fuel.
When you bonk, almost all of your glycogen stores are depleted, blood sugar level drops, (hypoglycemic), energy levels fall through the floor. Our muscles do have the ability to burn fat and protien as well as carbohydrates, however our brains need the energy provided by glycogen. When you truly and seriously bonk, you will find your vision blurrs, becomes fuzzy, your balance fails, feeling similar to being drunk. Often I have found that immediately before the onset of “the bonk”, I notice a short increase in energy, followed by a serious crash and burn. After you have bonked a few times, you will learn to recognize the subtle changes in your body that are warning signs to eat immediatley! If you find yourself in this situation, the quickest way to top up your blood sugar levels is but taking in some simple sugars. Simple sugars like glucose can even be absorbed into the blood strem through the stomach wall, even before it hits the small intestine. Sugary drinks, watever you can get your hands on will help. The trouble is, many people will actually feel slightly nauseated by this time and will avoid eating making the condition worse.

How to prevent it
Keep your bodies glycogen stores topped up before and during your ride.Our bodies will tend to burn a ratio of carbohdate to fat during endurace exercise. The higher the intensity, the more glycogen and the less fat your body will burn. By burning more fat, and saving the stored glycogen, you will last longer. “Fat burns in the flame of carbohydrate”Caffine has a known ergogenic effect on endurance athletes. It tends to tell the body to burn a higher percentage of fat than normal, which helps to conserve glycogen stores. Thats why you see professional cyclists having a cappuccino before races. Not to mention it tastes great.Not to turn everyone into caffine addicts, as habital use tends to lessen our bodies response.

These tips may apply to both on and off-road rides of lengths greater than 2 hours. Most of this is common sense, but sometimes common sense is, well, uncommon.These are things I have learned in my years of cycling. Most of them as a result of learning from mistakes and poor planing on my part. I would like to pass on these hard learned tips so that others may avoid making the same mistakes.

• Try not to ride alone, if you or another rider is in trouble there is someone there to lend a hand.
• Plan your route ahead of time, make sure everyone in the group knows the route. (We are working on some route maps for the next century ride!)
• Give your bike a quick check before leaving, fixing it at home is alot easier than out on the road or trail.
• Bring a basic repair kit, spare tube, and a quarter for a pay phone.
• Be sure to eat and drink properly before the ride, you don’t want to start out on a long ride even slightly dehydrated.
• Stay hydrated! A rule of thumb I found works is to drink 1 large water bottle of fluids every hour on the bike. Consider consuming some of your fluids in the form of an electrolyte replacemnet drink such as Gatorade, to help stave off muscle cramping. You may very well need more if it is hot out. Consciously remind yourself to drink during your ride, if you feel thirsty you are already dehydrated. Drink before you are thirsty!
• Bring plenty of food with you, eat regularly small ammounts throughout the ride, escpecially on longer rides, you should start eating earlier than you are accustomed to on shorter rides. Keeping your glycogenstores topped up really pays off. Avoid the dreaded Bonk!
• Pace yourself, warm up slowly, spin to win as they say. Save the pedal mashing for later on in the ride. Your legs and knees will thank-you for it later.
• Keep your upper body relaxed, no death grip on the bars or head bobbing. You ilw be less sore afterwards. Try to maintain good pedaling technique, spin circles, shift power to different muscle groups to minimize fatigue.
• Don’t forget to get out of the saddle one in a while, stretch yourself on the bike.