How to avoid bonking on the bike

Credit to Jim Linwood at Flickr for the image.

Despite what the Carry On films lead you to believe, bonking is not a good thing. Most cyclists do it at one point or another and once they have experienced it, they don’t want to do it again. That’s what this post is all about.

What is bonking anyway?

If you don’t already know, you have two forms of energy store. Quick energy that is stored in the liver and muscles as glycogen and slow release energy stored around the body as fat. Generally, we have around 60 – 90 minutes’ worth of energy stored as glycogen. Once this stores are depleted, your body needs to burn fat for energy.

Glycogen is a form of glucose sugar that is used by muscles to power them. It is also used by other organs for energy too, especially the brain. If you run out of this energy, bad things can happen.

Bonking is technically hypoglycaemia. This is when your body doesn’t have the ready supply of energy needed to fulfil the demands put upon it. When this happens, you immediately slow down and find it incredibly difficult to function. Your body restricts the final supplies of glycogen to fuel the brain, starving the rest of your body of energy.

Your muscles no longer have the fuel to function and you will begin shaking and sweating. You will find it exceptionally difficult to maintain momentum and control of the bike and may begin to experience dizziness and blurry vision. You will also find it incredibly difficult to continue pedalling.

Even though your brain has energy, it too begins shutting down which is why you may feel dizzy and get blurry vision. Needless to say, with the roads as they are, if you bonk you need to find somewhere safe to stop and get out of the road.

Other effects of bonking can include loss of balance, the desire to eat anything within reach, heart palpitations, anxiety, nervousness, hostility and tunnel vision. Good judgement can go out the window, as can self-control.

So as you can see, bonking on the bike is serious business. Take it from someone who knows!

What to do if you bonk

The first thing you need to do if you feel as though you’re bonking is to find a safe place to get off the road. Tell the others if you’re in a group or just get off the road if you’re not. Sit down and get some simple sugars into you right away.

Simple sugars include energy gels, Haribo, jelly babies or an energy drink. Get into the habit of carrying a small pack of sweets or an emergency gel in your pack. As soon as you feel the bonk, get it down your neck as quickly as possible. Sit still for a little while and let your body process the sugar.

Once you have ingested some simple sugars, now would be a good time to eat an energy bar or something with more complex sugars. Drink too.

On the mental side of things, you need to realise that you’re not operating on all cylinders. You need to remember that your judgement may be impaired and reactions slower than usual for a good hour or so. Either rest for that time, take it slow or find some quiet roads to ride. It’s difficult to remember all these things when you’re not thinking straight but it is important to do it if you can. If you’re with others, get them to keep an eye on you. If you’re riding alone, just be careful.

Preventing the bonk

I have spoken often about eating and drinking regularly on the bike during longer rides and this is why. I assume I have 60 minutes of glycogen in my system so will eat accordingly. When I’m out for an hour or more, I always carry something to eat in the form of protein bars, a packet of Haribo or something else. I also carry an emergency gel in my kit just in case.

To prevent the bonk, you need to eat properly before going out on a longer ride. You also need to take sufficient food to fuel you for that ride. You can add an energy drink to the mix if you like, but food is the most important.

Training-wise, you can teach your body to convert slow released energy quicker to help maintain energy levels. This should only ever be used to complement good nutrition and fuelling but is a useful addition to your arsenal. Fasted riding is just one example of how you can teach your body to speed up fat conversion for fuel and is worth considering if you go for distance in your rides.


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