Leading into this post, I promised myself that I wouldn’t try to dissuade people from running marathon(s) or any long distance races. I already do that plenty in other posts , so today’s is geared toward the folks that simply are going to run a marathon or marathons, regardless of what I say. I know these people exist because I used to be one. Running a marathon can be a huge bucket-list accomplishment. With that in mind, when people write in to ask me about training for a marathon, I think about what I would do in that situation knowing what I know now. How would I train to do the least damage and get the most benefit? Truth is, if I put my mind to it, and you had elite level potential, I could most likely train some of you to win the thing outright, but that’s not what this post is about. This post is about finishing the race without embarrassing and/or hurting yourself. It’s about accomplishing something big, something special. It’s about training for a decent, respectable showing in a marathon. One (or two, or three if you must) and done.
To be an effective marathoner – or even to just finish one – you have to be an effective fat burner . It is the beta-oxidation of fat , both dietary and stored body fat, that provides much of the aerobic energy you will need to maintain reasonable pace for 26.2 miles. I mean, 26.2 miles is a whole lot of miles. When you’re driving somewhere and the sign says “26 miles” to your destination, you think “That’s kinda close, but kinda far.” Now picture that on foot. Yeah. Good luck doing that as a fully dependent sugar-burner. Fat’s the ticket, and if you have spent the requisite few weeks reprogramming your body to derive most of your energy from fat while at rest and at low level of activity  (through your PB diet ), you will be primed to access fat while training.
With that in mind, you’re not really training for a marathon, per se – you’re training your body to become more efficient with its energy so that you can run a marathon. You’re actually reapportioning how your body uses various types of fuel at different activity levels. Thus, training for a marathon comes down to three primary goals:
1. Achieve mitochondrial biogenesis and optimality.
Increasing the number of mitochondria  (biogenesis) will spread the aerobic workload – the beta oxidation of fats and some glucose/glycogen – across more cellular power plants. Improving the number and efficiency of your mitochondria will allow you to do more output (running) with less reliance on glucose and/or glycogen as a primary fuel and more reliance on fat (input). In effect, this will increase your “miles per gallon.” Only instead of filling the tank with gasoline, you’re using stored body fat.
2. Increase the amount of fat burnt relative to carbs at a given work output.
Glycogen depletion is the defining point of “hitting the wall,” so you want to avoid the wall as long as you can. Remember, it’s 26.2 miles. The more fat you’re able to burn and turn into useable energy, the less glycogen you’ll go through. Muscle glycogen storage is very limited, and whether you’re a sugar-burner or a fat-burner, you’re still going to store the same amount of glycogen – it’s the rate at which you deplete it that counts. If you can access fat more efficiently and use fat for work that would normally require glycogen, you’re winning. If you can train to use fat for higher workloads, you can increase or maintain the intensity without dipping too deeply into your muscle glycogen.
3. Increase your aerobic threshold.
The aerobic threshold is the maximum level of output at which you are still relying primarily on the aerobic, or oxidative, energy pathways. As long as you stay under that aerobic threshold, you can train yourself primarily using fat to generate ATP energy  (and your high fat diet plays a key role here, too). Once you cross that threshold you start burning more sugar. As you get further into anaerobic territory, however, you’re burning mostly sugar – liver and muscle glycogen. Sugar burns faster (and hotter), and it doesn’t last nearly as long as fat. So if you can increase your aerobic threshold, you should be able to increase the intensity of your runs without dipping too deeply into your glycogen stores. Ideally, then, a prospective marathoner will train to increase his or her aerobic threshold (we’ll save the ANaerobic threshold discussions for another day). That way, you can save the glycogen for the finish line, when it really matters.
One way to start out is to simply keep your heart rate at or below 65% of your max on longer runs (and this might eventually become 70-75% of max as your training benefits accumulate). To determine a person’s aerobic threshold, I find the most intuitive way is to have them run “long” (6-12 miles after a few weeks of sufficient low level training) runs on back-to-back days on fewer than 150 grams carbs per day. If you can complete both runs, both days, without adding back extra carbs, you’ll know you haven’t been dipping too deeply into your glycogen stores. If so, that’s your aerobic threshold pace. Remember it.
As for a specific training prescription, here’s what I’d do every week, beginning at least 12 weeks before the event and generalized for the widest possible audience:
1. Two to three slow aerobic threshold runs.
These should be easy runs performed just below or at your aerobic threshold at the type of pace you can easily maintain. If you are just starting out from little run training, these sessions can be long hikes with easy jogs thrown in. These are great opportunities to just log mileage and improve fat oxidation efficiency without too much stress, where you can actually think about stuff other than the run (hey, maybe even work through some personal issues). For improving mitochondrial efficiency and stimulating mitochondrial biogenesis, these aerobic threshold runs (and your Primal Blueprint eating strategy) will be your bread and butter – the kind of low-level training I referenced in the post on improving mitochondrial efficiency through exercise .
To really promote fat oxidation, limit your carbs or even go into these runs in a slightly fasted state. When you begin dipping into glycogen, or hitting the wall (which might come soon-ish since you’re fasted or slightly carb depleted), back off. You want to stay away from the anaerobic pathway. The length of these runs will depend on your baseline endurance, and you’ll soon be able to stay under the aerobic threshold for longer (which is the whole point!). I would add a mile each week to the longest of these runs.
2. One interval session, followed by an active recovery day.
Run intervals one day a week – alternating repeat 400 m one week, 800 m the next. Walk or jog for two minutes in between. For the 400s, start with as many as you can comfortably do the first week and add one each week until you are at 12 intervals for the workout; for the 800s, work your way up to 10. On a scale of 1-20 with 20 being the most intense, keep the intensity at about a 14-16. It’s not an all-out sprint, because, well, good luck sprinting 800 meters multiple times, but this is at faster than your intended marathon race pace for sure. The next day, go for a walk or hike or go bike somewhere. Don’t go climb Half Dome or anything. Keep it pretty light.
For the intervals, you’ll definitely want to carb-load the day before. Slam the sweet potatoes and yams , about 400 carb grams worth, since you’ll purposely be blasting through your glycogen that next day.
3. One race-pace run.
Here, you’re trying to emulate the race pace without going the actual distance. It’s necessarily higher intensity than your regular runs, just at or slightly above your aerobic threshold. It’s going to be tougher, too, with some glycogen depletion. Don’t expect to pull out your iPhone and check Facebook in the middle of it.
Start with at least two or three miles, or a bit more than whatever length your threshold runs are, and add a mile each week (minimum).
If you plan on doing this barefoot or in minimalist running shoes, be absolutely certain your lower body is acclimated to it. A marathon is a long way for someone whose feet, calves, knees, and hips  (with all the connective tissues that go along with said joints and body parts) have only been spending cursory time exercising without protective footwear. Review my post on making the barefoot transition  and confirm that your ship is in shape.
Well, that’s what I’ve got. Remember, this is just general advice for the wider public. If you were my client, I’d tailor the training to you, but you’re not. For what it’s worth, this is how I’d train myself I were crazy enough to get back into running marathons, because it’s effective, it’s low-cost, and it’s actually a fairly healthy way to go about training for one. I mean who doesn’t want rockstar mitochondria ?
Any runners out there? Any marathoners? How do you train?
Next time, I’ll discuss how to fuel a marathon while staying Primal. And yes, it’s very possible.
Whew, and I didn’t even mention the phrase “Chronic Cardio ” once. I’m pretty proud of myself. Thanks for reading.