Calories and the Wall

The “average” runner on a “typical” course burns through about 100 calories / mile. So, in a marathon, you burn through about 2,600 calories. I was thinking of all the delicious ways to put those calories back on, when suddenly some things started to make sense. I put the wall, which usually hits at about mile 20, with the 2,000 calories you’ve burned so far, and put that with 2,000 calories the average person burns through on a typical day. So, in some sense a 20 mile run is within the bounds of reasonableness for your body.

I found this fascinating! No wonder a lot of marathon plans have the longest run being 20 miles. And no wonder your body does “weird, wild” stuff before you get to 26.2 miles. Because burning 2,600 calories is in no way typical. No matter what we are capable of doing, we (the vast majority of us) just don’t practice running 26.2 miles often enough to get used to it.

26.2 miles is well outside of typical. 26.2 is even bigger than 24, the number of hours in a day.

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2 Responses to Calories and the Wall

  1. Tad says:

    I have always read that the 20-22 mile limit on long runs has to do with avoiding the wall, as well as the increased injury risk of running fatigued. The 3 hour limit on long runs (which I subscribe to) is another good rule of thumb. I have felt that wall 3x now, and it’s not easy. Have you ever seen this? It’s pretty famous. If you can’t take the John Tesh narration, just turn down the volume. If you think the Marathon Wall is bad – “tri” the Iron Man Wall:

    Crazy training idea – if someone is running their first marathon and is scared of the wall, why not simulate it with enough fasting to hit it at less than 20 miles? I admit that doesn’t sound like a good idea for the uninitiated…

  2. neltow says:

    My stream of consciousness is… (1) The moment demands poetry. And someone who can pull it off. (2) Wendy Ingraham who decides to crawl first “beats” Sian Welch. (3) The “stalker” comment is reminiscent of persistence hunting. (4) The goal is to get the chip over the finish line. And it’s a game of inches.

    That is a perfect reminder (and both an inspiration and a cautionary tale) of just how far you can push your body and what the wall can look like. I recently watched Ultramarathon Man, where Dean Karnazes runs 50 marathons in 50 states in 50 days. In it, he recalls his final mile of a 100 mile race. He crawled.

    All this is making me rethink how far to push my long runs. 3 hours seems like a good upper limit. In 2011, I had some runs that went for 2:40. I’m also thinking I won’t be training enough to “get used” to the wall. But hopefully, I can train to be ready for the wall when it comes. And I’m not fasting prior to my runs, but I am doing “glycogen depletion” runs on my cutback weeks. 4 weeks ago, I had nothing but salt water on an 8 mile run. Forty minutes in, I was HUNGRY. This week, I’m planning on 11 miles.

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