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What the Bonk! You Hit the Wall in a Marathon. Now What?

Posted by George Parker on

I have hit the Wall twice in my thirteen marathons, and those races are seared into my memory.

The infamous marathon Wall: that slow-motion feeling of looking down at your legs, wondering why they will not turn over as if you are churning through one of those childhood pits of plastic balls. Runners experience the Wall differently, but almost universally, there are heavy legs and a sudden onset of fatigue. More ominously is the negative voice inside your head scolding you to slow down while simultaneously hurling damaging insults of doubts and insecurity. Sounds painful, right? Maybe not as painful as physically slamming into a brick wall, but the feeling is close – and lasts longer.

Our bodies rely on glycogen to fuel running, and we can store about 1,800 to 2,000 calories worth of glycogen in our muscles and liver. A typical runner burns 100 calories per hour. The Wall stakes its ground around Miles 18 to 20 of the marathon, where your body risks depleting its glycogen reserves. There are strategies you can incorporate to minimize hitting the Wall, but that will be the focus of another article[1]. Here I tackle what you do once you hit the Wall.

You hit the marathon Wall because your glycogen reserves are nearly depleted. Your brain panics and enters self-preservation. It increases the production of serotonin to signal fatigue and inhibit muscle fiber contraction. Once you recognize the signals, you can act quickly.

Slow down, consume calories, and refocus your mind.

If you have them, take your gels or other nutrition you are carrying. Whatever pre-race nutrition plan you had is now gone. It is time to eat and drink. Walk the aid stations, drinking multiple cups of sports drinks for the precious sugar and calories.  Most likely, your brain will also be screaming obscenities at you. Try to be nicer to yourself. Hitting the Wall happens to everyone; berating yourself will not get you through the experience faster. Instead, refocus on solving this problem. Maybe you will not achieve your goal time, but your race is not over. Having A, B, and C race goals is essential to switch your focus as the marathon unfolds.

I hope you never bonk and hit the Wall in a marathon. If you do, you can still have a great result. In the 2022 California International Marathon, I smacked into the Wall early at Mile 18. We battled for eight miles as I fought to take enough calories to maintain momentum as my glycogen reserves ran on fumes. My quads and glutes were screaming in agony, and the negative self-talk from my brain was ruthless and eviscerating. I finished the race slower than my goal time, but I still snuck in a Boston Qualification standard. My time was not what I was most proud of. I battled against myself for over an hour to cross the finish line. That race is seared in my memory – in the most positive of lights.

In the warrior's code
There's no surrender
Though his body says stop
His spirit cries, never
Deep in our soul
A quiet ember
Knows it's you against you
It's the paradox
That drives us on
It's a battle of wills
In the heat of attack
It's the passion that kills
The victory is yours alone

 [1] Avoiding the wall comes down to three variables: pre-race glycogen loading, in-race fueling, and glycogen vs. fat-burning ratio. Your muscles and liver can store 1,800 to 2,000 calories of glycogen, so the higher you get to 2,000 before race day the better. Training your muscles with a higher-carb diet and carb-loading the week before the race is important. Next, the typical runner needs at least 2,600 calories to complete a marathon. You must consume calories during the race. I aim for 30 – 60 grams of carbs per hour, which I accomplish by taking a gel every 30 minutes and sipping a sports drink at every aid station. Finally, perhaps most importantly, you must train your body to burn fat instead of glycogen at your fast marathon pace. Glycogen is a precious and diminishing resource. However, even the leanest of athletes have an ample supply of body fat to fuel the marathon distance. A central purpose of your long-training runs and marathon tempo efforts is to condition your body to not only rely on glycogen for fuel. The more your body can supplement fat burning with glycogen consumption, the longer your glycogen reserves can extend.

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