This is what bonking is like

Moving from Halloween to running, I wanted to blog about what it’s like to “bonk” or hit the wall while running a marathon. I’m a slow runner. Hell, I’m a slow walker. I consider it a great marathon if I finish in just under five hours. This past weekend at the Morgan Hill marathon, I bit off more than I could chew.

The morning of the race, I saw a pacer who would be running the race in four hours and forty minutes. Pacers are cool: they actually carry little signs on wooden sticks that say “4:40” or whatever. I thought “Hey, why not try to do this race in 4:40 instead of 5 hours? If I get tired, I’ll just slow down and fall back.” That was my first mistake.

My second mistake was forgetting that Morgan Hill has 400 feet of hill climbing in the first half of the marathon. To finish a marathon in four hours and forty minutes, you would need to maintain a pace of about 10 minutes and 40 seconds per mile, or 10:40. Running a 10:40 mile while climbing uphill is very different from running a 10:40 mile on flat ground.

The running pacer did a great job of keeping our little group of 4-5 people on a solid 10:40 gait even up the hills. Heading toward the final hill, we were even ahead of our overall 4:40 goal by about a minute. But I’d been pushing faster than I preferred to go (at one point dropping below a ten minute mile), and I’d been running up hills for half a marathon.

Just as we started to head up the final hill after mile 14, I bonked. I tracked the race with my Garmin 620 watch, and you can see what it looked like on these graphs:

Garmin graphs

In the top graph, you can see that I kept a steady, consistent pace until about 14 miles in. The middle graph is the elevation–even as we climbed 400 feet, the pace stayed pretty constant. Then you can see my collapse. My pace dropped off sharply. In the bottom graph, you can see how my cadence alternated between walking and jogging. I was lucky enough to find a friend for the last three miles of the race, and you can see my walking cadence sped up as we walked, jogged, and visited for the tail end of the race.

I might still be able to do a flat race at 4:40. And I might be able to do a hilly race at my previous best of ~5 hours. But attempting to run a hilly race in 4:40? That was too much for me that day.

So I got to see what it felt like to hit the wall, and it wasn’t fun. Instead of gradually running slower, I felt like I needed to walk to catch my breath. When I started running again, no matter how slowly I ran, my heart rate quickly spiked back up and I soon had to take another walking break. It was pretty humbling. The Morgan Hill marathon isn’t as tough as Whiskey Row (now that looks like a tough race!), but it was hard enough for me.

13 Responses to This is what bonking is like (Leave a comment)

  1. Kev

    Oh fantastic Matt!
    The word ‘Bonk’ translates so very differently in the UK!

    Very funny post indeed as a result 😉

  2. Hi Matt, great post but you will find that bonking sometimes refers to something quite different here in the UK. Prehaps you might google it 🙂

  3. Disappointing, Matt. To “bonk” means something completely different in the UK.

  4. Todd Mintz

    Your post is a wonderful metaphor for SEO :.)

  5. Indeed, I started reading this post with something very different in mind…made for a confusing minute this morning 😛

    The graphs from the Garmin 620 are really cool…too bad it’s a bit out of my price range though I think.

  6. Impressive Matt. I can’t even imagine running for 4-5 hours straight!

  7. Chipper Nicodemus

    I bet you can get a 4:40 at CIM! Nice flatter course w/ a few rolling hills. Best of luck!

  8. Todd Scott

    My guess is you became dehydrated. It can feel similar to a bonk. Your legs can get heavy and your heart rate increases. If you run harder than typical, you lose more water to sweat and respiration.

    When I bonk, my heart rate drops as one would expect. A gel pack or any simple sugars get me back up to speed fairly quickly.

    When I dehydrate, the top of my head tingles and it takes some steady drinking and time to rehydrate.

  9. Terrific post, Matt. I did Google “bonk.” In sports, in the UK and the US, “bonking” means “hitting the wall.” In the UK and the US, the verb “bonk” means to hit someone or something. For example, “He bonked his head.” In the UK and the US, the word also means “sexual intercourse,” which is an activity seldom practiced during a marathon. 😉 Keep running and writing, Matt. You are doing great!

  10. Haha, all the British people in here lowering the tone. Must say I thought the same thing at first.

    The information you got from your Garmin 620 looks awesome, very interesting!

  11. I’ve worn a heart rate monitor a few times when playing squash and when I push too hard against a player stronger than me, hitting my peak heart rate (~200bpm) guarantees I’m going to lose the match.

    A squash game moves so fast that there is insufficient time between points for your heart rate to recover. As soon as you start moving again, it peaks and you’ve just got nothing to give. No matter what your brain is telling your body to do, it just isn’t capable of delivering – slow to move, no power, poor accuracy – everything falls to pieces.

    I feel your pain Matt!

  12. Such posts from some greats make us realize that creativity is everything. That bonk word led me read every bit.

  13. I bonked and couldn’t pedal another stroke

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