How To Avoid Bonking & Retain Your Competitive Edge

Have you ever been part way through a race or event and simply found you could not continue? Did your legs feel like lead, you feel extremely tired and may even get the shakes or feel dizzy. If you weren’t expecting it you may not really know what is happening but it is highly likely that you are bonking or hitting the wall as it is sometimes known. This is when your blood sugar levels dip very low and your body is not able to recycle stored glycogen fast enough to produce more glucose for fuel. In this blog we are going to explain why it happens and how you can avoid it plus give you fuelling strategies to enhance your performance.

"being chased through the forest by a pack of wolves"

Bonking can be pretty grim even if you are only watching it happen to other athletes. I saw it happen during a mid-winter ultrarunning event where some athletes had covered over 100 miles and many were starting to run out of energy. Not only were many suffering GI distress at this point in the race, others were near collapse and at least one thought they were being chased through the forest by a pack of wolves!

 Although feeling exhausted and your legs are no longer working properly are often the first signs of a bonk,  in the extreme your brain can be involved too, you may start feeling confused, or even disorientated and in the extreme people have been known to hallucinate.

What Does the Science Tell Us About Bonking?

Bonking occurs when we deplete our sugar supplies. Carbohydrates in our diet breakdown into sugars and if not burned immediately are stored either as fat or glycogen. Going faster and increasing the intensity of activity burns more glycogen than fat. This is often why marathon runners get to around the 20 mile mark and start to struggle as they have to shift from burning glycogen to burning fat which takes more oxygen and is a slower process to generate energy.

Some glycogen is stored in the liver but most is in our muscles and we mainly use it when we are engaged in high intensity exercise, mostly above 65% VO2 max.

Burning glycogen uses less oxygen than burning fat and so if we run out of glycogen supplies we need to start using fatty acids. This process can release a lot of energy but the downside is it takes more oxygen which means you have to slow down to enable sufficient oxygen to be used to burn the fat supplies. Ultimately this means you have to slow down.

Striking the Right Balance for Endurance Sports

In endurance sports you are on the go for a longer length of time and there is no way you can complete an ultra run by fuelling on sugar alone. So whereas a sprinter or a boxer only needs a few seconds or minutes to make their mark with endurance sport fuelling the body becomes more strategic. Ideally you want to be able to swap from burning carbohydrates to burning fats as easily as possible so that your back up fuel reserve is available when you need it. Studies show that although everyone has a personal threshold it is possible to train yourself to switch to fat oxidation sooner and get more efficient at using fat as a fuel. Science now suggests that they key to this is metabolic flexibility which means being able to use either carbohydrates or fat as a fuel when you need to.

Reading this you might be tempted to go onto a Keto diet with a very high fat and very low carbohydrate ratio but a recent study of elite fat adapted athletes in race conditions found that they were not as successful as those not on a ketogenic diet. This is likely because although burning fat is great for going the distance in endurance events and perhaps helping you finish it is not going to give you the fastest time if you really want to win.

When you burn fat you create more energy per fatty acid burned than from the equivalent glucose sugar molecules. So you actually get more energy from fat but it takes longer to produce!

Another thing to consider is that the body is not just burning one fuel or another most of the time, it will be burning a combination which is why being able to use both fuels is probably the best way forward.

How Can You Keep A Competitive Edge

I am going to suggest two strategies that can help support your body to get through a race and get your best result on the day:

Train Low and Race High

By this I mean do most of your training on a low carbohydrate diet (50 – 120g/day) ideally and increase the carbs when you do a particularly intensive training session. This is known as carbohydrate periodisation and will help you become more efficient at burning fat. In the long run this will help fuel you on a long endurance event.

Fuelling Strategies for Performance

In the run up to race day you want to preload with more carbohydrates to make sure your glycogen supplies are topped up. Ideally do this for a couple of days before hand and the morning of the race.

For race day make sure you have a tried and tested fuelling strategy, don’t do anything new on the day that you have not already tried out beforehand.

Aim to have a sports drink that has a 6% glucose formula, so 60g sugar per litre of water. Try to avoid fluorescent looking commercial drinks packed with additives and instead make a homemade drink with coconut water, fruit juice, honey, water and electrolytes. 6% seems to be the magic number for increasing performance and delaying onset of fatigue.

For longer events have some homemade solid fuel that is easy to eat such as cooked potato, flapjack, brownie or bananas. Again with longer events such as an ironman or ultra you might want to think about adding in some protein powder to your sports drink or mix it into your flapjack or brownie mixture. There is no clear evidence yet on whether the protein makes a significant difference so you may have to experiment with what works for you.

Now that we are all getting ready to get back out on training rides and even back to events try out some of this in your training sessions to see what works for you.

Moira Newiss - Nutrition: Optimum Energy & Performance

If you want to get some expert sports nutrition advice then check out our founder Moira Newiss website over at where she offers nutritional therapy services to help with energy and performance.

Antichafing Sport Body Balm

Getting set up for training again you will also want to make sure you don’t chafe, so check out our antichafing Sport Body Balm which is super effective at preventing chafing for all sports and is made with natural and organic ingredients. Good for you and good for the planet!

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