Marathon season is upon us and we at Salty Running know our readers take their marathon performances seriously! So over the next few weeks, we’ll be featuring articles about how to prepare for your fall marathon. From training tips, to picking a race, to what to wear, we’ll be your go-to source of information for your big fall races!
Our first topic in the series is how to train to prevent bonking. Have you ever bonked? Hmmm. Wait. Maybe you don’t know what bonking is (besides an obnoxiously goofy word). Let me tell you a story.
Last October I lined up for my fifth marathon. I was in the best shape of my life. Three weeks earlier I ran 16 miles averaging 6:47 and felt FAN-f’in-TASTIC. I was so ready. How naive I was. My goal was to average 6:50 for the marathon. I was doing well, running 1:29:30 at the half (averaging 6:51 pace). I was chugging along and then right around that magical two hour mark things got weird. I felt dizzy. I felt heavy. I felt insane. I felt drunk. I felt crampy and nauseous and just bad. I could. not. go. It wasn’t just a matter of needing to slow down either. No, I ran out of gas and basically Ginger’s boyfriend James and Pepper had to tow my sad sorry self to the finish line in 3:11:47. I went from 6:50’s to somewhere over 8:00’s in a matter of moments.
What happened to me?
I wasn’t just tired or over it or not tough enough. There was no mind over matter this time. My body ran out of glycogen. Glycogen is the carbohydrates (sugars) our bodies primarily use to fuel our muscles when we run. Typically, a trained athlete stores enough glycogen in her body to get through 2 hours of harder running. So with no added carbs, most of us would bonk at the 2 hour mark of a marathon.
But I did add carbs! I took two gels prior to bonking (we’ll call this point in the race, Point Bonk). With the extra 200 calories of carbs, I should have made it past the two hour mark, right? Well, not necessarily. You see, when we’re running hard and our bodies aren’t used to fueling on the run we might not be able to digest those carbs. My body might have been too busy keeping my legs moving and my brain from going into overdrive (something I struggle with in the longer races) to metabolize the gels I took. Also, when I returned to my hotel room I noticed the half a bagel and half a Clif Bar sitting on the table. Perhaps part of the problem was that my tank wasn’t full when I hit the starting line.
This isn’t the end of the story though. Let’s use an analogy to cars. Our bodies aren’t like my old VW Jetta. Our bodies are more like a Prius. A Prius’ primary fuel is gas, but it’s back-up fuel is a electricity. For people, the primary fuel is glycogen (sugar, carbs, whatever you want to call it), while our back-up fuel is fat (chub, blubber, whatever you want to call it). Our bodies can burn both glycogen and fat at the same time, an act they almost always do unless we’re running really really fast–like sprinting. What’s cool is that we can train our bodies to burn fat more efficiently, This is key because if we can train our bodies to burn more fat efficiently, there will be more glycogen to burn later in the race. We push off Point Bonk somewhere past the 2 hour mark. And if we can train our bodies to metabolize carbs that we ingest while running too, we can make it all the way to the finish line without running out of gas–without bonking.
Although actually experiencing a bonk was kind of neat in that I felt like a living science experiment, I would suggest you do everything in your power to get to the finish line of your fall marathon with a little sugar left in the tank. “But what can I do now to avoid bonking in my fall race? ” you might be asking. I might answer, “Good question!” and then continue with this: based on my experience and research there are three things we can do before the marathon to avoid running out of glycogen and bonking.
1) Train our bodies to burn more fat and to reserve glycogen.
It’s pretty simple to teach your body to burn the chub rather than the fuel. You run when you’re glycogen tank isn’t full. There are a couple of easy ways to do this. Run long without taking in carbs, run doubles without replenishing your glycogen stores fully in between runs, or back-to-back longer runs (2 runs of 90 – 120 minutes on two consecutive days). The latter two options are for advanced runners only. The easiest and best option for most of us is to do several long runs without taking in sugar (gels, sports drinks, etc.)
2) Learn how many carbs to take in during the race and practice taking them to make sure your body can metabolize them.
It’s really easy to teach your body to metabolize sugar. Do some long runs with some marathon-paced running during which you do take in a gel or two and\or sports drink.
3) Make sure your glycogen stores are full before you hit the starting line.
This is the easiest of all: eat the entire bagel and the Clif Bar before the race! Also, the days before the marathon are no time to diet. Even though you’ll be tapering and not burning as many calories, you still need to eat lots of carbs. We’ll help you out with a pre-marathon diet in the weeks to come.
Simple Bonk-Prevention Marathon Workouts
Ok. So now you know that you need to train your body to burn fat and to metabolize sugars on the run, here are some actual workouts you can incorporate into your training plan to bonk-proof yourself for race day.
Fat-Burning: It will take several weeks to work the fat-burning system. When you run at an easy pace you don’t burn through your glycogen as quickly as you do when running marathon pace, so you can actually do your long runs without carbs. It might not be pretty, but it’s an important lesson to teach your body. Here is an example of a three-week progression of long runs that will train your body to use fat to fuel you on the run:
- During 1 week run 2.5 hours easy without ingesting carbs during the run.
- During week 2 run a total of 2.5 hours without ingesting carbs and run easy until you have 2:10. From there run marathon pace for the last 20 minutes of the run.
- During week 3 do the same 2.5 hour run without ingesting carbs and up the marathon-paced portion to 30 minutes.
Sugar Metabolizing: This system doesn’t take as long to train as the fat-burning system. One or two workouts will do, especially if you already take energy gels or drink gatorade while running regularly. Here is a sample workout that will train your body to metabolize sugar at marathon pace:
- Run a total of 20 miles. Run the first 10 easy, then run 8 at goal marathon pace taking a gel 2 miles into the marathon paced portion. Run 2 miles easy to cool-down.
If you’d like to read more about bonking, fat-burning, or glycogen stores check out these links:
- Science of Running, Evidence for Doubling, Training in Glycogen Depleted State
- Runners Connect, Marathon Fueling – How Not to Bonk
- Science of Sport, Fat-burning 101
- Marathon Guide, Fuel on Fat for the Long Run
Have you ever bonked? Do you always take in carbs during your long runs? Think you might try to train yourself to burn fat more efficiently by not taking in a gel or sports drink during some of your long runs this training cycle?