In the cycling world, a bonk is not a good thing. It essentially means ‘hitting a wall’ in a physical and emotional sense, meaning that you find it very difficult, if not impossible, to carry on. If you are planning to do some long cycle rides (over about 90 minutes) or indeed join us on one of our cycling holidays, it is essential that you learn about bonking as it is best avoided at all costs.
As funny as it my sound, bonking is actually very serious and is what cyclists and other endurance sportspeople call hypoglycemia. Essentially it means that 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 for about 90 minutes of moderate exercise. Anything longer than this and you will need to take in some more glucose for your body to function correctly.
The symptoms of a bonk can vary, but on a physical side you will generally feel extremely weak and tired and you may shake, sweat a lot and feel dizzy or light-headed. You may also have heart palpitations and will probably be very hungry. Bonking can also affect the brain as that too burns glucose, and you may feel anxious, irritable, confused and emotional. At the very extreme, a bonk can induce a coma, so it is vitally important that you look after your body, learn what it needs to function properly and understand how to avoid a bonk.
The first thing you must do if you feel a bonk coming on is ingest some simple carbs that your body can quickly absorb in order to raise your blood glucose levels again. Simple carbohydrates include food such as energy gels (make sure you drink water with these), jam sandwiches, sugar cubes or sweets such as jelly beans. More complex carbs, such as energy bars, take much longer for the body to process into glucose and so are best avoided at this point in time. If you identify that you are about to bonk and manage to catch it early, you should be able to carry on cycling whilst ingesting your simple carbs. However, if you have missed this window and are showing more serious symptoms, it is important that you get off your bike and give yourself a bit more of a chance to recover.
As long as you have caught the bonk early enough and have successfully ingested some simple carbs you should be able to recover fairly quickly and carry on with your ride. However, you must be especially aware about what you are taking in for the rest of the ride and ensure that you refuel often. Eating lots of high carb foods at regular intervals of 30 minutes or so will ensure your glucose levels do not dip again. You should also be aware that even though your body may have recovered and you feel ok, your mental faculties may not have been fully restored and your awareness and sense of the world around you may not be back to normal. It is therefore important to take extra care, especially on busy roads.
In cycling, there is never a truer word than the saying ‘if you’re hungry, it’s too late’. The best way to avoid a bonk is to eat little and often during your bike ride and crucially make sure you eat before you feel hungry. This means ingesting about 100-250 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. You may think you’d never forget to eat, but you might be surprised at how easy it is to forget on our cycling holidays when you’re coursing past beautiful sights. Some people like to set an alarm on their watch to remind them, but just be aware that the more you ride, the more energy you will use up and therefore the more you will need to replace. We always encourage our riders on our cycling holidays to make the most of the cake at designated stops and also take a handful of sweets (which our support crew always carry with them!) to pop in your pocket or saddle bag in case you need them. It takes practice to get into the habit of eating whilst cycling, but the consequences of forgetting to aren’t worth risking.