As an endurance athlete, you are familiar with the feeling of fatigue. It’s typically a sign that you are pushing your body and working to improve your fitness. Though fatigue is normal, bonking is NOT.
Bonking, or “hitting the wall,” is an extreme condition when your body becomes depleted of its energy stores. It goes beyond the feeling of heavy legs and shortness of breath, and it can be a scary experience as the body begins to work against you.
My name is Sarah Katz, and I am a registered dietitian who works with athletes to help prevent bonking during long training sessions and endurance races. In this blog, we will cover:
- What is bonking?
- Why bonking is bad
- How to avoid bonking
Before learning how to prevent bonking, first, let’s discuss what bonking is and why it happens.
What is bonking?
The body primarily stores energy from carbohydrates in the form of glycogen in the liver and muscles. (1) When you exercise, glycogen is broken down into glucose, which is then used by the muscles to produce adenosine triphosphate (ATP) – a big word for energy. The release of ATP is what allows your muscles to contract and produce movement. (1)
Most individuals can store about 600 grams of glycogen, which is about 2,400 calories. However, factors such as sex, body size, and muscle mass can impact the amount of glycogen that your body stores. (1) For intense activities, such as repeated sprints, glycogen stores may be depleted in an hour, whereas endurance activities like marathon running may not deplete stores as quickly.
When glycogen depletion occurs, your body will break down other sources of energy that are not as readily available–primarily fat and, in some cases, small amounts of protein. Because of this, exercise intensity cannot be maintained, and the symptoms of “bonking” begin to set in. (1)
Symptoms of Bonking
- Extreme weakness
- Dizziness
- Nausea
- Shakiness
- Brain fog
- Poor coordination
Bonking is unlike normal fatigue in that no amount of mental grit can propel you through it. The body physically cannot endure anymore and begins to slow down. Extreme weakness, dizziness, poor coordination, brain fog, and nausea are symptoms associated with bonking. (2) As you can imagine, it’s not a pleasant feeling, and it can also prevent you from crossing the finish line on race day.
Not only does bonking affect you physically and mentally, but it also has health consequences. Next, let’s talk about some of the short- and long-term health consequences that happen when you bonk.
Why Bonking is Bad
Being an athlete often requires pushing past limits during training and on race day. When this leads to bonking, you sacrifice not only that session but also future sessions–and possibly your hard-earned race day.
When your body becomes depleted, stress hormones, such as cortisol, become elevated, and your body enters a ‘catabolic’ state in which it begins to break down other substrates, like protein and fat, for energy. (3) Though this may not sound too bad, being in a catabolic state for a prolonged period of time can lead to:
- Muscle loss
- Increased risk of injury
- Impaired immune function
- Extreme fatigue
- Delayed recovery
Proper nutrition and hydration can help your body bounce back from a bonk, but it usually takes 24-48 hours for glycogen stores replenish. If you are short on time for training delays or on a rigid training plan, each training session is valuable. While missing one or two training sessions may not have significant physical effects, it can delay your progress and disrupt the flow of your plan.
In addition to the physical consequences of bonking, the mental component can be just as impactful. A true bonk is scary. It can be challenging to push yourself after knowing what it feels like to push too far. Creating a plan to avoid bonking is a great way to ease the mind and prepare the body for the effort that is to come.
Finally, let’s discuss how to avoid bonking with proper nutrition and hydration!
How to Avoid Bonking
To avoid a bonk, all you have to do is provide your body with enough fuel to meet your needs during training and throughout the day. Seems simple, right? Unfortunately, many challenges may limit your ability to properly fuel and hydrate during training sessions and the day. It’s important to find a plan that works for you or work with a registered dietitian to help you make a game plan for daily nutrition and race nutrition.
3 Tips to Help You Avoid the Bonk on Your Next Long Training Session or Race
- Begin every workout well-fueled.
Eat a snack with about 30 grams of carbohydrates 30 minutes before a workout. You may also consider carb-loading in the days leading up to a big race to ensure your glycogen stores are full. Need help developing a carb-loading plan? Our team at Victorem Performance Nutrition is here to help! - Fuel and hydrate during every training session lasting over 1 hour or high-intensity training sessions.
Delay glycogen depletion by consuming carbohydrates during training. Try a variety of gels, chews, drink mixes, or other quick carb snacks to find what you like.
Aim for 30-60 grams every hour for training that is 90-120 minutes.
Aim for 60-90 grams every hour for training that is 2+ hours. - Prioritize recovery after EVERY training session to make sure you replenish glycogen stores, rehydrate, and repair broken down tissues.
With a well-developed plan and a basic understanding of what causes bonking, you can make sure that you are taking the necessary steps to give your body what it needs to perform at a high level for long durations.
Conclusion: The Home Stretch
Think of bonking like a car running out of gas and a marathon like a long road trip. Planning your stops to make sure you have enough gas on your route ensures that your car doesn’t run out of fuel or break down, so you can make it to your destination smoothly and safely.
Treat your body and your next long training session the same. Plan your fuel and hydration to ensure your body has enough ‘gas in the tank’ to carry you to the end.
If you are not sure how much fuel you need or how to plan your nutrition for your next race, meet with one of our registered dietitians specialized in endurance training, or get started with a ready-made race day nutrition plan created by a sports dietitian!
