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 saddlebag 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.
August 9th, 2015 at 6:59 pm
Good to know after I experienced my first bonk. Hate it!!!!!!!
Thanks
April 19th, 2016 at 2:07 pm
Good advice. It’s extremely hard to eat and drink enough. Focus on ‘real’ food such as small easily consumed peanut butter or cream cheese finger sandwiches, rice cakes , dates, fruit smoothie pouches such as Ellas Kichen for kids. M&S wine guns scored high in a recent article about glucose content so carry small sweets such as these or jelly babies toix in with some real food.
May 19th, 2016 at 5:15 pm
I honked on my first sportive, not a good state to get in. Now I eat and drink lots. The advise on ride25 is invaluable. Eat Drink and No Bonking!
September 18th, 2016 at 4:06 am
I run out of energy at the 40 mile mark on a 50 mile ride this week and had to stop and rest and eat the only thing i had with me,dry oats and water.After reading the advice about 100 to 250 cals every half hour,i think i will take a six pack of fruit tea cakes on my next 50 mile ride.
October 1st, 2019 at 10:27 pm
Experienced this today after a 25 mile ride at the Erie Canal. I’m over 60. Came home and crashed and slept. Will take this a lot more seriously.
April 30th, 2020 at 9:20 pm
Experienced my first bonk 4 days ago about 20 miles and an hour and a half into a 32 mile ride. It was scary, and came on so fast. I was just a little tired, and felt a little hunger, but I’ve ridden longer, and faster in hotter weather, and it wasn’t awful, so I ignored it, then all of a sudden my vision started to tunnel and I was seeing stars and I could not go any more. Like everything just stopped, and my muscles would not listen to me and my vision was going black. I had to stop and eat a trail mix bar I had with me and sit for a few minutes, and still got lost on my way home and kept mixing up left and right, and getting turned around. For 2 days after, I could not seem to eat enough to get full, and felt starving to the point of my stomach feeling hollow about every 2 hours, and I couldn’t push past a 10 mile ride both days no matter how hard I tried. I took yesterday off, and may try a short ride today, but I am definitely going to take this seriously in the future.
May 12th, 2020 at 8:51 pm
It happened to me about two weeks ago it was definitely a bonk BUT not as i know a bonk.
I had been riding back wind for about an hour every thing was fine i turned the corner into a strong head wind after about a hundred yards it was like hitting a brick wall i thought i was going to die,I did not pass out. Sitting down on the side of the road some one brought me a chair to sit on .After 15 mins i seem to come round i ate an apple and called someone to come to rescue me. If thats a bonk not as i know it… I HAD ONE …
A lesson here always carry sweets or sugary bar .
May 15th, 2020 at 8:08 pm
Will you please comment on how to fuel BEFORE the ride? What’s the best way to start do one doesn’t crash too soon?
June 12th, 2020 at 6:03 am
Just experienced my 1st bonk at the end of a HIIT session. I normally have a good few mins before I reach the line. Today, my legs turned into Jello. I slowed down and tried to recover to finish. Not happening.
I’m eating my carbs and staying hydrated always. Skip lunch on a busy day- pay a high price.
July 21st, 2020 at 10:04 am
Hi does anyone know if this can hit you the next day 🥴 as I went on a tuff ride and never ate or drank but felt ok but the next I was sat in my work shop talking and suddenly felt sick past out and face planted the concrete floor and then spent about seven ours in hospital having loads of tests and looking like crap does any think this was from the bike ride ????thanks
August 2nd, 2020 at 9:32 am
The nice information about cycling and for the take of organic foods its the good advice to the biking and cycing people
October 21st, 2020 at 9:58 am
It fully explaining about bonking. very nice article.