Video: How Do I Avoid the Infamous “Marathon Bonk?”

The 2008 New York City Marathon was one of the worst experiences of my life.

I was cocky even though my training was sub-par. I under-fueled and ran several tough miles too fast (fine… WAY too fast).

After the 20 mile mark, I bonked hard. Every step sent excruciating shock waves of pain through my legs.  The last 10k of that marathon felt like 100 miles.

The 24th mile was run at an agonizingly slow pace of 7:09 and I struggled to finally finish in 2:44:38.

My soul was crushed and my legs were beat. I spent the next six months with IT Band Syndrome, wondering if I’d ever run again.

Fast forward three years: I just passed the 22-mile mark of the Philadelphia Marathon, clocking a 6:01 for the previous mile. I finished the final 4 miles strong and clocked a 2:39:32 finish.

I never once bonked, hit the wall, or experienced significant leg pain.

In other words, it was a polar opposite race than NYC. What did I do differently? How did I pull a complete 180 in performance?

Many runners are asking the same questions. The marathon is like a unicorn: once you catch a glimpse of a good race, you won’t stop until you finally run one successfully.

Brad had a similar question. He asked me:

What’s a good leg strength routine to assure a strong finish in the final 10k of a marathon? I did my first marathon this past Sunday and my legs died before my heart.

Here’s my response:

My God my face looks huge

There are a few key takeaways to learn about how to finish a marathon strong and avoid the classic bonk.

  • Fueling is essential. Most runners don’t carb-load enough! Practice your fueling during your long runs (here’s how to plan your long run nutrition).
  • Running 1-2 20 milers is the bare minimum. Run up to 22 miles and run some of those miles at your goal race pace.
  • Overall volume is important – don’t expect to run a good marathon on 25 miles per week.

The right marathon workouts can help prepare your body for the demands of 26.2 miles. Instead of 5k paced intervals or other VO2 Max work on the track, it’s more beneficial to focus on aerobic sessions like tempo and progression runs, with limited speed workouts.

Finally, I have to recommend that you run conservatively during the first half of your marathon if you want to have a strong finish. Running too fast at the start, or putting “time in the bank,” is a flawed strategy and will certainly leave you struggling during the last 10k.

Instead, start slightly slower than your goal pace for the first 2-3 miles and find your rhythm for the rest of the race. If possible, speed up after the 18th or 19th mile ever so slightly. When you hit mile 22 or 23 and if you’re feeling good, run even faster.

At that point, rely on your fitness and mental toughness to get you to the finish – there’s no need to be conservative with just a few miles left. But remember that the last 10k of a marathon will be tough – there’s no sugarcoating the difficulty of 26.2 miles.

Strength Work for the Legs

Brad was looking for specific leg exercises to help him have a better final10k in his next marathon. I think these are secondary to the training and nutrition tips above, but they’re crucial for injury prevention and stride power.

My favorite exercises and specific routines for the lower body:

The runners I coach are very familiar with some of these exercises. They help you stay healthy and prevent injuries – the #1 goal of this type of work.

The secondary goal of this ancillary work is to address any particular weaknesses or imbalances you might have. Running magnifies your weak areas so be proactive with your strength work.

Thank you for the question Brad and good luck with your next marathon!

PS. You can still download the book 13 Lucky Racing Tips for Your Next Personal Best here – for free.

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  1. Carbo-load is overrated! It is not for everyone.
    Keto-adaptation is the best thing for some athletes.
    I suggest you read these books:

    • That’s fine for general health, but it’s not appropriate for marathon racing.

      • Well, I have never run a Marathon. Only 35K. I consumed only carbs (dried fruit) during those 35K.

        What I am saying is that some people will suffer if they carbo-load. If I eat a lot of bread and pasta for two or three days before a race I will have sinusitis and headaches. And that’s not only me. There are thousands (if not millions) of people that say that they suffer if they eat too much carbs (see

        But for carb-adapted people, carbo-loading may be Ok.

  2. Wow, I wish i would’ve read this post before my last marathon! I definitely experienced the marathon “bonk” or wall. My dreadfully slow last two miles was never ending, but it certainly taught me a lesson! Thanks for the post. I am still trying to figure this whole marathon thing out. There is so much that goes into it!

  3. Jason due to illness I was unable to complete my one 20-miler. During this training cycle my longest long runs were one 17-miler, and one 18-miler. You mentioned 1-2 20-milers is the bare minimum. My marathon is in 2 weeks. Do you think I should not run this marathon because I didn’t do the bare minimum? Is it inevitable that I will “bonk” because my mileage was short?

  4. I’ve never had a “good last six miles” of a marathon. Maybe that will be my goal this year 🙂 oh, and sub-4 (2nd try) would be nice too. and your face looks big? really? lay off the twinkies 🙂