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How to Avoid Hitting the Wall During a Marathon
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How to Avoid Hitting the Wall During a Marathon

Some marathon runners may be all too familiar with the experience of hitting the wall, also known as “bonking”. Hitting the wall is a sudden and dramatic decrease in energy and performance when muscle glycogen stores are depleted, which can prevent runners from performing at their best in a race or finishing the race at all. This blog will cover what you need to know about how to avoid hitting the wall.

A 2021 study analysed over 1.9 million runner’s marathon data and found that 28% of male runners hit the wall compared to 17% of females, speculating that it’s because men are more likely to pace too aggressively. There was also a strong correlation between the likelihood of hitting the wall and PB times of runners in the 3-5 hour range, indicating that it’s not just first-time runners that hit the wall. Finally, the study concluded that faster (sub-3-hour), more experienced runners are far less likely to hit the wall due to better preparation.

With proper preparation, it’s possible to avoid hitting the wall and maintain a strong performance throughout your entire marathon. In this blog, we’ll discuss the key factors in preventing you from hitting the wall such as increasing your carbohydrate intake before and during your race, staying properly hydrated, pacing your race properly, training intelligently and using caffeine in the latter miles to ensure your most successful marathon yet.

Caffeine Bullet Founder David Hellard after winning a marathon

Marathon Nutrition: Fuelling To Avoid Hitting The Wall

Proper nutrition before and during a marathon is crucial to helping you avoid hitting the wall. The body relies on glycogen, a stored form of carbohydrate, as a key source of energy during endurance exercise, so it’s important to start the race with high glycogen levels and to limit glycogen depletion during the race by consuming carbohydrates during the race. However, it’s important to understand that increasing your carbohydrate intake isn’t as simple as just shovelling as much pasta in your mouth as you can, you also need to ensure your stomach can tolerate the excess food you’re taking in.

If you consume too much or the wrong type of food you’re more likely to experience “runner’s stomach”. During long races it’s common to experience gastrointestinal issues, this is because during exercise the body diverts blood flow away from the stomach and intestines to the working muscles. This decreased blood flow decreases motility (movement of food) of the stomach and intestines, which can lead to feelings of discomfort, pain, and bloating. So it’s important to make sure you stick to a well-thought-out plan that allows you to take in enough fuel and the right types of fuel to ensure you avoid hitting the wall and feel comfortable throughout the race.

Nutrition In The Days Before Your Marathon

Your nutritional goal in the days leading up to the race is to maximise your glycogen stores for race day, to minimise the chance of glycogen levels dropping too low during the race. As you’ll be consuming a lot of carbohydrates and overall calories in this time, it’s recommended to lower your protein and fat intake slightly in the lead-up to your race to reduce the stress on your digestive system.

It’s recommended to “carbohydrate load” in the days leading up to the marathon, as you’ll be training less and consuming more carbohydrates, your body is better equipped to store the excess carbohydrates as muscle glycogen.* Aim to consume at least 6 grams of carbohydrates per kilogram of body weight per day in the 2 days leading up to your race.* Runners more experienced with consuming higher carbohydrate intakes can carbohydrate load with 7-12 g/kg body weight of carbohydrate per day, only aim to consume what you’re confident you can handle.

If you’re worried about GI distress on race day, a useful alternative to traditional carbohydrate loading is to consume 10-12 g/kg body weight of carbohydrates 3 days before your race and consume a moderate (6 g/kg) in the 2 days before your race.* This reduces your risk of issues on race day, but obviously may be uncomfortable and impractical to attempt to take in such a high amount of carbohydrates in one day.

When carbohydrate loading, aim to consume a combination of low glycaemic index (slow digesting) and high glycaemic index (fast digesting) carbohydrates, it may help to keep your fibre intake slightly lower than usual to minimise bloating, for example we recommend any combination of:

  • Pasta
  • Bread
  • Rice
  • Sweet potato
  • Oats and Porridge
  • Chickpeas
  • Dried Fruits
  • Potatoes
  • Fortified Cereals
  • Bagels
  • Popcorn 
  • Soreen
  • Pretzels

While it may feel uncomfortable at the time, proper carbohydrate loading is hugely important if you want to avoid hitting the wall.

Nutrition In The Hours Before Your Marathon

The hours before your race are your final chance to “top-up” your glycogen stores, it’s important to ensure you don’t eat too much just before your race as you increase your chances of becoming bloated and having stomach issues.

Aim to consume 1-4 grams of carbohydrates per kilogram of body weight in the 1-4 hours before your race.* We recommend starting at the lower end if it’s your first marathon and working your way up as you become a more experienced racer. If you’re aiming for the higher end of the spectrum, try to consume a combination of glucose (e.g. grains and cereals) and fructose (e.g. fruits and fruit juices) to increase the rate of carbohydrate absorption.* Aim to consume mostly high glycaemic index, low fibre carbohydrates to ensure you don’t struggle with feelings of fullness during your race, this can be any combination of:

  • Fruit juices
  • Bananas
  • White pasta
  • White rice
  • White bread
  • Bagels
  • Soreen
  • Pretzels
  • Sports drinks

Nutrition During Your Marathon

During the marathon, it’s equally important to maintain proper fueling by consuming carbohydrates throughout the race. This will help to maintain blood glucose levels and spare muscle glycogen, which is crucial if you want to avoid hitting the wall.

A general guideline for carbohydrate consumption during a marathon is to consume 30-60 grams of carbohydrates per hour, which can be achieved through the use of sports drinks, gels, or other carbohydrate-rich snacks. More experienced runners can consume up to 60-90 grams per hour if practiced beforehand.

It’s important to “train your gut” to improve how effectively you absorb carbohydrates during your training runs, we recommend that you practice your nutrition on most of your long runs. You should aim to practice your full nutrition strategy more than once in your training – don’t just have 1-2 gels and call it a day, as you won’t be giving your gut a stimulus to improve carbohydrate absorption. This also allows you to replicate how you’re likely to feel on race day, so you can make any adjustments to your race-day nutrition plan if needed. We also suggest practicing your nutrition on your longer marathon-paced runs to get an even more accurate picture of how you’ll feel on race day and you can assess how practical your food choices are at race pace (e.g. carrying too many gels can lead to a sticky mess in long races).

Only aim to consume as much carbohydrate on race day as you’ve done in your training as your gut may be unable to handle more than you’ve trained it to. Aim to consume high glycaemic index carbohydrates with low fibre contents as they are much easier to digest, commonly used carb sources during races are:

  • Bananas
  • Sports drinks
  • Energy gels
  • Energy chews
  • Raisins
  • Honey
  • Dried fruits
  • Energy bars
  • Sweets e.g. Jelly beans or Haribo

If you’ve practiced it in your nutrition during training, you can also consume a combination of glucose and fructose to increase the rate at which you absorb carbohydrates. Because glucose and fructose are absorbed in slightly different ways in the body, you’re able to absorb up to around 90 grams of carbohydrates per hour when combining different types of carbohydrate sources.* Here are a few examples of carb sources to achieve this:

  • Energy gels: Look for gels that contain a blend of glucose and fructose, in a 2:1 
  • Sports drinks: Many sports drinks contain a combination of glucose and fructose.
  • Whole foods: Some whole foods, like bananas or dried fruits, contain a mix of glucose and fructose. 
  • Homemade fuel: You can create your own fuel by mixing glucose and fructose sources, such as honey and dried fruit, into a homemade energy gel or bar.
  • Energy chews: Some energy chews, contain a mix of glucose and fructose for optimal absorption.

A lesser-known tip for race-day nutrition is to have a variety of different flavours and textures to eat during your race, this breaks up the monotony and sickliness of eating the same food over and over again and gives you something to look forward to. So we also recommended experimenting with a mix of sweet and savoury foods to help you eat more throughout the race.

David Hellard Caffeine Bullet Founder during a marathon

Try a Carbohydrate Mouth Rinse During Your Marathon

When you rinse a carbohydrate solution in your mouth for 5-10 seconds before spitting it out, receptors in your mouth activate and stimulate your central nervous system which can potentially enhance your performance. 

Studies have shown that carbohydrate mouth rinsing can slightly improve exercise performance in endurance athletes, by reducing perceived exertion, increasing motivation, and delaying fatigue. The mechanism is thought to be related to the activation of brain regions associated with reward and motor control, leading to an increase in voluntary muscle activation.

Since carbohydrate mouth rinsing does not require digestion, it may be a useful strategy for you if you experience gastrointestinal distress during your race, particularly towards the end when the thought of consuming another gel is enough to make you feel sick. 

Further research is needed to fully understand the benefits and optimal application of this technique for marathon runners, but rinsing a carbohydrate solution in your mouth for 5-10 seconds, several times throughout your race may help you perform slightly better when struggling to take on more carbohydrates.

Use Imodium Before Your Marathon

Using Imodium can help to manage symptoms of diarrhea during your race. Diarrhea can be a common issue for marathon runners, as it can obviously cause discomfort and significantly impact your performance. By taking Imodium, you may be able to reduce or eliminate diarrhea symptoms, which can allow you to focus on your running and continue to consume carbohydrates throughout the race with a lower risk of developing GI issues.

Other Factors Contributing To Hitting The Wall

Whilst nutrition is the most frequently talked about factor regarding hitting the wall, there are numerous other factors such as hydration, training, pacing, sleep, and the use of caffeine which will also have a huge impact on your overall performance and likelihood of hitting the wall.

How Staying Hydrated Helps You Avoid Hitting The Wall

Dehydration leads to a decrease in blood volume which can contribute to an increase in heart rate during your marathon – known as cardiac drift, causing you to fatigue faster.

However, if you’re running a normal city marathon, it’s unlikely you’ll become dehydrated enough for your performance to drop significantly. Recent research suggests that you need to lose more than 2-3% of body weight in sweat before dehydration influences your performance.

To stay hydrated, a general guideline is to aim to consume approximately 500 ml of fluids 2-3 hours before the start of the race, and then drink to thirst during the race. Common sports drinks are often lower in electrolytes than you’d expect so it may be worth using electrolyte tablets and powders to help replace those lost in sweat for hot and humid races. Alternatively seasoning your water or sports drinks to taste using table salt can help stabilise your sodium levels as lower blood sodium levels are often more of a concern than dehydration.

However, hyponatremia (low blood sodium) is also unlikely if you’re not consuming excessive amounts of fluid, you’ll likely be fine just drinking to thirst unless you have undergone a sweat test that indicates you lose a lot of sodium in your sweat.

David Hellard Caffeine Bullet Founder struggling with dehydration in the desert

How To Structure Marathon Training To Avoid Hitting The Wall

To prepare for a marathon, it’s important to train using a well-structured training plan to ensure you’re physically prepared for running the full distance at your goal pace.

It’s essential to run at least one long run weekly to increase aerobic capacity, increase the number of mitochondria and capillaries in the muscles, and improve overall endurance. 

We also highly recommend running at least one 18 to 20-mile run in your training helps your body adapt to the mechanical stress of the marathon, allowing your muscles to become more resistant to damage and fatigue. From experience and anecdotal evidence, we’d suggest running at least 2-3 18-mile runs in your training plan if looking to improve your PB.

Approximately 80% of your training should be performed at an easy pace – a conversational pace at an effort level of about 3-4/10. To find your easy pace you can start with running at 60-70% of your maximum heart rate or at a pace 5-10% slower than your marathon pace. We also recommend scheduling recovery runs into training weeks that you’re finding particularly challenging, you can learn everything you need to know about easy and recovery runs in our blog.

Finally, you need to be training at your goal pace frequently to improve running economy, allowing your body to become more efficient at using carbohydrates and fats as fuel, delaying the onset of fatigue whilst running at marathon pace. Training at goal pace also improves your mental preparedness and confidence in maintaining the desired pace throughout the race.

How To Pace Your Marathon To Avoid Hitting The Wall

If you start your race too fast you’ll be using a higher proportion of carbohydrates as fuel, leading to a much faster depletion of glycogen stores early in the race, increasing your risk of hitting the wall later on when compared to a more conservative pace. To avoid this, it’s important to establish a sustainable pacing plan, helping you conserve glycogen stores early on.

Ensure you have a pacing plan that includes starting slightly slower than your ideal average race pace. It’s also important you start in the correct pen and you’re familiar with any unique characteristics (hills, sharp turns or weather, etc) of the race course. Remember that in a busy marathon, it might be unrealistic to be able to run at the pace you want for the full duration without weaving through other runners – expending more energy than necessary, so take that into consideration when planning your pacing strategy.

How Improving Your Sleep Helps You Avoid Hitting The Wall

It may seem obvious, but ensuring adequate sleep (at least 7 hours) the night before your race can make a big difference to your performance on the day. Inadequate sleep can increase cortisol levels in the blood, which can increase the breakdown of muscle glycogen, contributing to a higher risk of hitting the wall. Try to practice good sleep hygiene habits (e.g. limiting screen time an hour before bed and sleeping in a cool, dark and quiet room) in your training and in the lead-up to your race to put the odds in your favour for a good night’s sleep before your race. 

How Caffeine Helps You Avoid Hitting The Wall

Most runners end up running the second half of their marathon slower (a positive split), although they may not intend to! 

Caffeine improves performance by stimulating the release of adrenaline, leading to an increase in heart rate, blood flow, and the breakdown of fats for energy allowing you to spare muscle glycogen.* It also reduces your perception of pain and fatigue, making it a great second-half fix to help you maintain race pace in the final half. 

The International Society of Sports Nutrition has reported that consuming a moderate dose of caffeine (3-6 mg/kg body weight) significantly improves endurance performance, recent research suggests that you can also see performance improvements with dosages as low as 1-2 mg/kg body weight. However, for a marathon we don’t recommend taking the optimum caffeine dose in a single dose, instead spread it over 2-3 doses throughout the race to reach the optimum dose. This ensures you benefit from caffeine for as many miles as possible and helps you avoid a caffeine crash.

It’s important to know how much caffeine to use and when to take it when, so you can plan the best caffeine strategy for your race. Ideally, you’ll want your blood caffeine levels to peak just as you need a boost, so knowing how to time your caffeine intake is crucial. We recommend taking a first dose of around 100 mg between miles 15-18 and a second, larger dose of 100-200 mg between miles 21-23. 

Bare in mind the best time to consume caffeine depends on what source you use. You can consume caffeine from gels or tablets during the race, however caffeine from these sources takes 45-60 minutes to peak in the blood,* which means you need to time them accurately, anticipating when you’ll need a boost. Alternatively, you can use a chewed form of caffeine, which kicks faster as caffeine is absorbed through membranes in the cheeks and gums as you chew, allowing to enter the bloodstream faster and peak in as little as 15 minutes. For more information about caffeine timing check out our blog When To Take Caffeine During a Marathon

It’s common at the end of a marathon to no longer be able to take on more fuel due to nausea and discomfort, therefore we recommend separating your caffeine sources from your carbohydrate sources. This way you’re not relying on gels as your caffeine source, so even if you feel sick you can still get your caffeine doses in.

That’s why we created Caffeine Bullet, to create an easy way to take in caffeine when you can’t stomach another gel. We recommend 1 Caffeine Bullet between miles 15-18 when you start to tire and another 1-2 bullets between miles 21-23 to ensure you can still finish strong. Because the caffeine is chewed, they kick 3x faster than gels and pills and with 100 mg* of caffeine per energy chew, you’re able to quickly and accurately dose your caffeine to prevent you from hitting the wall. 

How To Avoid Hitting the Wall During a Marathon

To avoid hitting the wall, marathon runners should:

  • Consume 6-12 grams of carbohydrates per kilogram of body weight per day in the 2 days leading up to the marathon.
  • Consume 1-4 grams of carbohydrate per kilogram of body weight, in the 1-4 hours before the race.
  • Consume 30-60 grams of carbohydrates per hour during the race.
  • Use a well-structured training plan that includes at least one long run per week and at least one 18-20 mile run in the plan.
  • Frequently train at goal race pace.
  • Don’t use an overly aggressive pacing plan
  • Consume a moderate dose of caffeine (3-6 mg/kg body weight) spread throughout the second half of the race.



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