What is Bonking? And What Causes Runners to Hit the Wall?

Bonking, also known as hitting the wall, is an unpleasant experience for any runner. It can happen to new runners who are just starting out, or experienced athletes taking part in a long-distance run or race.

When it happens, it often takes the form of sudden exhaustion and an inability to continue running. The physical symptoms can range from mild dizziness and disorientation to full-blown collapse.

Bonking is caused by depleted glycogen stores in the body, which can happen if a runner does not take on enough carbohydrates during a long run. It’s important to be aware of the signs of bonking and what you can do to prevent it from happening since it can not only hinder your training but also impact your health.

In this article, we’ll discuss what bonking exactly is, what causes it, what exactly it feels like, and how you can better support your body to avoid it during runs and marathon training.

What is Bonking?

Bonking is a phrase used to describe the functional depletion of glycogen caused by exercise. It’s when your muscles essentially run out of fuel, which has serious consequences for your health and ability to perform.

The term ‘bonking’ is commonly used by runners to refer to a shortage of energy or the point in a race when the legs cramp. But although bonking is not a scientific term, it does have a precise meaning, and all of these symptoms fall within its umbrella but that’s still not what bonking truly is.

Excessive fatigue during a regular run is usually an indication that you are pushing yourself too far beyond your limits and maybe even running at a faster pace than you’re currently capable of. This could lead to symptoms similar to bonking, but it’s still not what bonking is.

Bonking typically occurs only on longer runs when energy supplies are completely depleted. After going through it once, you won’t be able to forget it, and you won’t want it to happen to you ever again.

What Causes Bonking in Running?

Bonking occurs when glycogen, the body’s carbohydrate energy stores, is reduced to an ineffective level.

Even with the most severe bonk between 10 and 30 percent of the initial glycogen supply still remains in the muscles. But, unfortunately, the lack of accessible energy prevents the muscles from functioning normally and runners experience bonking.

The reasons behind this phenomenon are still being researched and debated. There are two main theories as to why this occurs.

The first is known as the ‘catastrophe model,’ which comes from studies conducted by Nobel Laureate Sir Archibald Vivian Hill and colleagues in Manchester, UK in the 1920s. According to this theory, bonking and exhaustion occur when muscle function reaches its physiological limit and begins to fail.

Another theory has been put forward by more recent studies published in the Journal of Experimental Biology. This theory suggests that the brain serves as a ‘central governor’ to limit the muscles proactively, shutting them down when energy resources run short to prevent damage.

No matter what caused it, the effect is significant and can affect runners quite adversely.

What Does Bonking Feel Like?

A true bonk is more than just feeling exhausted or having tired legs. It’s a state of complete inability to keep going, accompanied by nausea, acute physical weakness, poor coordination, and a deeply unpleasant feeling.

Bonking is essentially hypoglycemia or low blood sugar caused by exertion. In most cases, bonking is preceded by escalating waves of symptoms.

You may initially experience physical symptoms like feeling hungry or mental symptoms like engaging in negative self-talk, which gradually leads to an increase in your rate of perceived exertion (RPE).

Plus, you could have a muscle-glycogen bonk where you’ll feel like your brain is working just fine but your legs have started to give up. Or, on the other hand, you could experience a blood-glucose bonk where your legs are working just fine but your brain seems to be giving up.

Eventually, you’ll experience a complete bonk with not only mental fatigue but also physical fatigue and exhaustion.

When the severity of a bonk increases, you may experience a variety of unpleasant symptoms including dizziness, shaky hands, nausea, a decline in focus, and even headaches. If the bonking persists, the risks of disorientation and physical inability increase.

It’s important to know what bonking feels like, not just for your health and safety, but also because the sooner you figure out what’s wrong, the faster you can fix it.

Symptoms of Bonking

• Nausea
• Dizziness
• Headaches
• Shaky hands
• Excessive physical weakness
• Extreme fatigue
• Poor coordination
• Loss of focus
• Decline in cognitive functions

Why Bonking is Dangerous for Runners

The effects of a bonk can be devastating. It not only feels horrible in the moment, but it also has a negative impact on your general health and well-being. Bonking can ruin not only a run, workout, or race, but also your training and how well you do in the future.

Muscle Loss

Bonking can actually lead to muscle loss. According to research, the body enters a catabolic stress state during exercise. Cortisol increases blood glucose levels, making more of the body’s carbohydrate fuel accessible for hard efforts.

If you don’t eat enough carbohydrates, your body’s metabolism changes to burn other fuels, like fat and, eventually, protein. This is a condition in which the body essentially consumes its own muscle as an energy source.

It goes without saying that this is not ideal, given that we need to use our muscles to run more efficiently and to prevent injuries.

Impaired Immune Function

During training, the immune system helps the body adapt, and exercise can help make it stronger. But bonking and overtraining can hurt your immune system.

According to studies, prolonged, intensive exercise can decrease the body’s natural anti-inflammatory response. Your body’s immune system protects you from harmful bacteria and viruses to prevent infection.

Researchers further iterate this by explaining that if you overtrain and weaken your immune system, you are more likely to get sick or get an infection.

Disruption in Training

Training builds on itself, and each workout in a training plan is designed with the next workout in mind. Bonking throws off this rhythm by causing a lot of unproductive stress, fatigue, and exhaustion.

The mental toll of bonking can be just as crippling as the physical. As runners, we frequently test the limits of what we believe is possible. Your brain may use the incredibly unpleasant feeling of a bonk as the discouraging association it needs to impose additional limits further hindering your training.

What’s even worse is that it frequently results in circumstances that are just plain unsafe. Temporary mental and physical impairment develops as cognitive function declines alongside muscle capabilities. And so, vision, judgment, and balance can all be compromised.

Physical Pain Caused by Exhaustion

Physical pain caused by exhaustion can be both acute and chronic in nature. Acute pain is usually caused by muscle fatigue, cramps, and spasms due to overexertion or running too much mileage too quickly.

Chronic pain can come from overuse injuries such as tendonitis or lower back issues. Both types of physical pain can be extremely uncomfortable and can make running even more difficult.

What’s worse is that research shows that overall stress from the increase in cortisol can worsen existing health issues, and it can even increase the sensations of physical pain within the body.

Dehydration

In many cases, bonking is associated with dehydration, since runners and other athletes who don’t eat enough frequently also don’t drink enough.

Glycogen itself is water-dense, therefore glycogen depletion limits the amount of hydration available in the muscles. The fatigue and other negative effects that bonking leaves behind are exacerbated by dehydration.

How Long Does It Take to Recover From Bonking?

Eating enough food and drinking enough fluids can alleviate the worst symptoms of a bonk, such as nausea and weakness, but this does not indicate recovery.

Bonking is, by definition, a major and disruptive event for your body, pushing you far beyond the stress of acceptable or productive training. This means that the effects of a bonk can last long after the immediate effects have gone away.

How long it takes depends on how depleted you let yourself become, but most bonks happen on longer runs, making things even more difficult. This implies that your body has to recover from your calorie depletion in addition to the significant training load of the run itself.

A bonk normally takes at least a few days to recover from, and sometimes much longer. It’s crucial to give your body the rest and nutrition it needs during this time because you can feel more run down, exhausted, and hungry than usual.

It’s important to note that your immune system may also be affected for up to three days after bonking, so treat your recovery seriously. If you become sick because of bonking could further hinder your training for weeks.

What to Do If You Bonk During a Run

If you start to bonk, remember that you can fix it by eating and drinking. Even though the body desperately needs nutrition, nausea often makes eating difficult during bonking.

You can avoid this side effect by drinking some liquids while eating. It normally takes the brain a few minutes after eating to start feeling better once your body has had a taste of replenishing carbohydrates.

If you bonk, don’t be afraid to call a friend or family member for a ride home. In the aftermath of functional depletion, ensuring your own safety should be your top priority.

In addition to potentially endangering you, running for miles to reach your home in a compromised state can make your situation worse and seriously delay your next training and overall recovery even further.

How to Prevent and Avoid Bonking

The easiest method to avoid bonking is to nourish your body with sufficient food and liquids during your run. This may seem simple, but in practice, it can be more difficult than you might expect.

Here are some tips that’ll help avoid bonking during a run or marathon training:

Better Training

Clearly, this is going to be the most obvious statement made, but you need to follow your training plan. You need to have a consistent build-up of mileage to peak week which is going to help your body adapt to the needs of race day.

Better Fueling

If you’ve done base building correctly, you’ve helped teach your body how to use a little more fat than carbs for fuel, which means you won’t need quite as much fuel on race day. And that my friends mean fewer porta-potty stops.

But as you increase the intensity, your body is going to start burning more carbs and looking for quick easy sources of energy. You don’t need to be taking in hundreds of calories per hour, but you do need to be giving your body some fuel.

• Eat a solid breakfast a few hours before the race to ensure your glycogen stores are topped off and you’ve got enough to not feel hungry!
• Start line fueling with pre-workout or caffeine
• Carry energy gels with you for a quick carb fix when needed
• Shot block or whole food option at 5, 12, 18, 23
• Take advantage of pre-workout supplement tools like caffeine for a boost

Better Pacing

You’ve heard that you need to stay in control during those first miles when the energy is high, but did you know it’s to help prevent hitting the wall?? Taking off in that initial surge burns through those quick carbs as your HR shoots way up and it expends too much energy.

• Make the first mile your slowest mile, likely won’t happen, but thinking that way will help you hold back.
• Try not to spend a ton of energy dodging other runners
• Settle into your goal pace quickly, rather than aiming for negative split
• Don’t try to pick up the pace until you’ve passed mile 21 still feeling strong

The Name is Funny…The Result…Can Also Be Funny

Splat. The noise reverberated throughout the neighborhood, causing a stutter in the step of thousands of nearby runners, who even without witnessing the event, knew what had happened.

A fellow runner had hit the wall.

This is not the wall of Humpty Dumpty or the wall that Trump would build. This is the narrow, easy to navigate around, if you’re focused on good training and nutrition, wall of the marathon.

Course officials made this statement “we don’t place the wall there intentionally, in fact, we spend a lot of time in emails and during the expo handing out information to help prevent this from happening. But we simply can’t monitor each individual runner.”

And of course because we all sign a liability waiver filled with legal jargon we don’t understand, the race cannot be held liable for the the Splat.

Luckily, medical staff was on hand and as the runner weaved wearily past their aid station, they stepped out to offer a nice warm paper cup of Gatorade. As the runner gulped the orange liquid dripping from their chin, mixed with less salty than normal tears, they started to smile.

No strike that, they started to dry heave.

Other runners have stated they believe the wall is fake. It’s a figment of the runners imagination and that our bodies can do so much more than we believe. And to them we ask, have you ever run a marathon? 99.9% said no because it sounded awful.

The runner noted at the beginning of this story could not be found for comment, but we have it on good authority (our own) that she finished the race on her own two feet. It wasn’t pretty, she wasn’t really all that happy about it, but she achieved the 26. goal.

And then proceeded to register for next years race because it was only $25 at the finish line and that’s a price you just can’t beat.

Listen running shouldn’t be so serious and hence the reason I like to make sure that sometimes we take a detour to laugh at ourselves.

Looking for more marathon training tips?

• Marathon Fueling Plan
• Marathon Pacing Chart
• What to Wear for a Marathon
• Best Marathon Training Plan?

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