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How to avoid hitting the wall and bonking in a marathon

How to avoid hitting the wall

Confession time: I’ve registered for four, started three, but only completed two marathons. Sadly, I’m not proud of either of my two marathon finishes.

Things were going well until mile 18 in both races and then I fell apart. My energy was sapped and I could barely move my legs. My pace tanked and it took all of my willpower to make it to the finish line.

I hit the wall big time. “Hitting the wall” or “bonking” is a sudden, intense loss of energy. You may also experience heavy legs, extreme weakness, and/ or dizziness.

If you’ve also hit the wall in a race, you’re in good company. Some estimates say that 4 in every 10 marathoners will bonk during the race. Yikes!

I’m giving the marathon distance another go this fall and my goal is to have an enjoyable marathon experience. So, I’m trying to learn how I can avoid bonking mid-race this time around.

Why bonking happens
Hitting the wall occurs when you’ve run out of gas. “Gas” in this case is glycogen, the stored form of carbohydrates in the body. Glycogen is the main source of fuel for endurance athletes. In other words, glycogen powers our bodies to run. When we deplete the glycogen stores in our liver and muscles in our legs, our body relies on fat for power instead. However, fat is much less efficient and requires more oxygen to convert to energy. So, runners slow down dramatically as a result.

Glycogen depletion usually occurs during marathons and other endurance events. Bonking most often occurs after the two-hour mark of steady state exercise, usually between 70- 85% of your VO2max. You can’t bonk in a 5K, for instance, because the body relies on different energy systems for short, more intense exercise.

Dodge the wall
Preventing bonking during a marathon is all about having good nutrition, both in the days leading up to the race and during the event itself.

Throughout training, aim for 60- 70% of your calories to come from carbohydrates. Think whole grains, fruits, vegetables, and dairy products. Also make sure you’re eating enough food overall. Not taking in enough calories can further deplete your glycogen stores. Fueling well during and immediately following runs can also help. Most importantly, be sure to eat and drink the same products at the same time on long runs as you will on race day.

However, figuring out what, how much, and when to eat to avoid the wall is often easier said than done. It will take some trial and error – and possibly even bonking during a race – to find the nutrition formula that works best for you.

What to do if you bonk during a race
Sometimes it’s possibly to partially recover from bonking during a race. You’ll need to refuel with something high in carbs, like a sports drink or gel or both. You may have to significantly slow your pace, stop, or even sit down for a few minutes while you try to bounce back.

If you hit the wall, don’t beat yourself up. Chalk it up as a learning experience and take heart in knowing that many runners have been in your shoes before.

Written by Jen Matz.

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