"You have to forget your last marathon before you try another. Your mind can't know what's coming."    -  Frank Shorter

 

Without a doubt, one of the most challenging aspects of running marathons is fear of “The Wall,” (fondly called the “bonk”) The good news is that like most fears, this one is best combated with knowledge and experience – both of which you will gain as you train for your race.

First, it’s really important to understand exactly what causes a runner to bonk, and for this I turn to Rick Morris, writing for Running Planet. His is the most straightforward explanation of “The Wall” I have found.

According to Morris, “Researchers have identified two primary causes of running fatigue – central and peripheral or more simply “brains and brawn”. Peripheral fatigue (brawn) is caused by chemical and physiological factors in your exercising muscles while central fatigue (brains) is associated with the efforts of your central nervous system (CNS) to maintain a homeostasis or “balance” of those chemical and physiological factors and prevent damage to your muscles.

“Causes of peripheral fatigue include hydrogen ion build up, accumulation of extra cellular potassium, muscle damage and hypoglycemia. Hydrogen ion and  potassium accumulation usually only occur at faster 5K and 10K race paces and are not typically a cause of marathon running fatigue. The main peripheral causes of marathon running fatigue and hitting the wall are muscle damage and hypoglycemia.

“The energy to power your muscles come from adenosine triphosphate (ATP), which is formed from the metabolism of fats and carbohydrates. Your body prefers to use carbohydrates, which are stored as glucose in your blood, and as glycogen in your muscles and liver. Unfortunately your stores of glycogen are limited.

“Most runners are able to store somewhere around 2000 to 2200 calories worth of glycogen in their liver and muscles, which is enough to energize about 20 miles of running.  When you run out of glycogen your body is forced to rely almost completely upon fat metabolism to supply energy.

“Fat supplies more energy per gram than carbohydrates, but your body is much less efficient at converting that fat to energy, so you begin to slow down and suffer from fatigue. So as you can see, it’s no accident that many marathon runners hit the wall at around 20 miles. That’s when they run out of glycogen and they become hypoglycemic.

“The initial effects of hitting the marathon wall and hypoglycemia are physical in nature. Your muscles fatigue and your pace slows. Your brain runs on glycogen just as your muscles do. Your brain takes priority over your muscles, so when you run low on glycogen, your brain will take what’s left and your muscles must fend for themselves. As your glycogen levels plummet even lower your brain begins to suffer from the effects of hypoglycemia and the wall. As a result your brain starts to feel like it’s in a fog. You become confused, your willpower drops and you may become very emotional. I have seen grown men crying like a baby in the final miles of a marathon.

“For many years peripheral fatigue was given the lion’s share of the blame for marathon fatigue and hitting the wall. Now, many researchers, led by Dr. Timothy Noakes, believe that central fatigue plays the largest role in hitting the wall. The theory behind central fatigue is that your CNS is making an effort to protect your muscles, your body, and also to maintain a chemical balance in your body. If it were up to us as runners we would run as hard as we could until we dropped from physical exhaustion. Our will to keep running would drive our muscles to their very limits. We would run until our damaged muscles and chemically out of whack physiology finally breaks down and collapses.

“That kind of catastrophic breakdown is not a healthy situation and it’s one that our CNS tries to prevent. Your heart and brain must have a source of glycogen to keep operating. When your CNS senses that you are becoming hypoglycemic or that you are pushing your muscles to the point of damage, it begins to cut off signals to your muscles. It forces you to slow down to protect your muscles, brain and heart. You sense this through feelings of fatigue. Your CNS is dropping the marathon wall down to keep you from reaching those catastrophic levels of chemical imbalance, hypoglycemia and muscle damage.

“It is also believed that your CNS not only senses physiological changes in your body, but it can also anticipate upcoming requirements and manage the signals to your muscle accordingly. For example, before a marathon your CNS calculates how much energy you will need to complete the race and “doles out” signals to your muscles at a pace that will allow you to finish without catastrophic system failures.  In a sense, your CNS is setting your pace.”

There now, don’t you feel better? NOT!

Remember that one of the most important aspects of your marathon training is to “teach” your body to conserve glycogen. Your base training improves the blood’s capacity to delivery oxygen and withdraw waste. Speedwork and long runs train you to push back the point at which you start becoming anaerobic – and teach you to deal with the discomfort and burden of lactic acid buildup (Galloway, Galloway’s Book on Running p.44).

Now, depending upon your experience level and whether or not you are planning a serious goal time will determine your relationship to the wall on race day. In fact, Rick Morris even goes so far as to suggest that if you are seriously racing the idea is not to avoid the wall, but merely push it off until you hit mile 26.

However, for most of us avoidance is probably the best policy. So how do you do that?

Tips for Avoiding the Wall

Take your weekly long runs seriously. Those progressively longer runs are your best defense against bonking. We previously discussed how important it is to  properly pace your race and conserve your energy up front. Your experience on your longer runs pays off big here as you are going to know exactly where your pace should be mile over mile. DON’T let the excitement get you…run your own race and conserve those carbs up front.

Take your diet and nutrition seriously. We’ve all heard the tales about “carbo-loading” before a big race, but the fact is that you need to pay attention to your diet from the time your marathon training first begins. This is NOT the time to diet or eschew carbs. (Ladies – some initial weight gain is not uncommon). Yes,  you should consume larger amounts of carbs in the last few days before the race, but none of that will matter if you have not kept yourself properly fueled and hydrated throughout training.

Runners can typically store about 1800 calories of carbohydrates, which will adequately fuel you for about 20-23 miles. While in training remember, 65-25-10. That’s the ratio of carbohydrates to protein to fat you should be shooting for. However, we’re not just talking ANY carbs. You want low Glycemic Index (GI) carb sources. Take a look at this list for an understanding of the kinds of foods you should be eating. You may even want to contact a sports nutritionist to provide some guidelines.

Yeah, carb load – but do it RIGHT!  Mega pre-race pasta and beer fest aside, there is a proper way to maximize the amount of carbohydrates your body will store before your event.

As you enter your final week of taper, begin decreasing your portions while maintaining that 65-70% carb ratio. Then, during the week just before your race, you can do a “super compensation” plan, which involves first depleting your muscles of carbs, followed by a loading period. Rick Morris suggests the following plan:

Decrease carbohydrate intake gradually from 60% to 40% of your total calories on days 1 through 3. Decrease your running duration from 60 minutes to 30 minutes during that period. On the following three days, increase your carbohydrate intake to 70% of total calories and decrease your running duration from 20 minutes to total rest. The result will be muscles that are “maxed out” in their carb storing ability. The best types of carbs to eat during your marathon taper are also low GI carbs so that your blood glucose levels maintain a steady state.

Final Taper Week

•                Day 1 – Exercise Duration – 60 minutes, Carb intake – 60%

•                Day 2 – Exercise Duration – 40 minutes, Carb intake – 50%

•                Day 3 – Exercise Duration - 30 minutes, Carb intake – 40%

•                Day 4 – Exercise Duration – 20 minutes, Carb intake – 70%

•                Day 5 – Exercise Duration – Rest, Carb intake – 70%

•                Day 6 – Exercise Duration – Rest, Carb intake – 70%

•                Day 7 – Race Day

 

Important note: exercise physiologists and professional coaches do disagree about the effectiveness of the depletion/load model, and some athletes report gastro-intestinal problems when following this method. As you know, research exists to be disproven so follow these links, do your own research, use your common sense and if necessary, consult a sports nutritionist.

Do right the morning of the race. It is thought that avoiding foods high on the Glycemic Index on race day morning is best. By now, you should have experimented with food before your long runs and you know what bothers you and what doesn’t. DO NOT FAST! A small amount of fat is good at this time– like a couple of pieces of whole-wheat buttered toast and a banana.

Remember, the time to consume those sports gels and shots high on the GI is during your race when quick energy is needed…and do not pass the water stations without stopping.

Whew! I know this is a lot of information – but there’s a lot of information out there. Just keep in mind what actually causes “The Wall” and follow proper and adequate training and dietary guidelines and you’ll greatly reduce your chances of experiencing this most feared marathon phenomenon.

READ MORE

The Science of Carbohydrate Loading

Avoid Hitting The Wall

Race Day Sports Nutrition

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