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The Bonk

If you find yourself or one of your group struggling with this, the outlook for the rest of your ride isn't good as your body is getting very low on fuel. The biggest problem is being dehydrated, which will drop your blood volume as it thickens. Your wee should be a pale straw colour. If it is dark yellow you're most probably dehydrated. If your hydration drops by just 1% you could lose up to 15% power. If you feel you have jelly or dead legs and you're losing power even on the flats (or significantly slowing down) and your heart rate is elevated, then stop and take a drink. Do not drink too much as this will just sit in the stomach and will take some hours to be absorbed. The absorption can be speeded up with a dash of salt (about 1/8th teaspoon) in 400ml of not chilled water. Please note that some sports drinks/gels can exacerbate the problem if taken post bonking. I add Dioralyte to my bidon, it contains Glucose, Sodium chloride, Potassium chloride. Please always read the instructions before using.

The second form of The bonk occurs when you are low on fuel (carbohydrates). The signs to look out for are you feel light-headed, and/or have tunnel / blurred vision. If this happens, you need to reduce your heart rate to under 130bpm so that your body can start to use your existing fat store, not your dwindling carbohydrate reserve. The quickest way to resolve this is to take a glucose tablet or say, four jelly babies. This will reduce the effects but you will still need to stop as early as possible to eat something more substantial to refill your carbohydrate store.

Lastly, the effects of coffee on performance are debated. Coffee can cause a problem for people who are dehydrated as it is a diuretic and will elevate your heart rate, which is not good if you're are suffering from the second form of bonking. Diuretics make your body produce more urine, and so will cause you to lose sodium and dwindling water store. When you lose too much sodium and water you become further dehydrated, which will, in turn, have an effect on a range of bodily functions, including temperature control and the absorption of food.

The third type of bonking is not covered on this website.... :)