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Could there be a connection between Radcliffe’s more aggressive nutrition strategy and her outrunning the greatest male distance runner of all time in the last two miles of the London Marathon? You bet. It is a simple, incontestable fact that the more fluids and carbohydrates a runner absorbs while competing in a marathon, the better he or she is likely to perform, especially in the critical closing miles.
Maximizing fluid and carbohydrate intake during a marathon requires that you first "train your gut" during the weeks of formal conditioning that precede race day. Unfortunately, this is something that few runners—even few elite runners—think to do. Logging hundreds if not thousands of miles in preparation for a marathon and then starving your muscles through it is not unlike building an impenetrable fortress and then defending it with the front gate open.
Never Enough
Runners are frequently ignorant of, or misled by advice such as the American College of Sports Medicine’s recommendation that athletes consume 30 to 60 grams of carbohydrate per hour during exercise. These guidelines make it sound as if 30 grams are just as good as 60. They also imply that the rate of 30 to 60 grams per hour matches the rate at which carbohydrate is burned during exercise, for why would the ACSM cap be set at 60 grams unless 60 grams were "enough"?
Here’s the reality. At marathon pace, a typical runner burns in the range of 200 grams of carbohydrate per hour. But the average runner can absorb only 60 to 80 grams per hour when carbohydrate is consumed in the most absorbable form—a six to eight percent liquid solution. So the ACSM guidelines are based not on how much carbohydrate you would need to absorb in order to prevent depletion but on a very conservative estimate of how much you can actually cram into your stomach without suffering gastrointestinal distress (cramps, bloating, nausea). The vast majority of runners don’t even get close to this.
The situation with fluid loss is similar. Body fluid (comprising water and electrolyte minerals) is often lost at rates exceeding 1.5 liters per hour during marathon-pace running. Yet the average runner is unable to tolerate drinking at more than a third of this rate while racing. Drinking any faster—even though the body could use a lot more fluid—causes uncomfortable stomach sloshing and can eventually result in cramps, bloating and nausea as well.
The bottom line is that you simply cannot get enough fluid or carbohydrate while running a marathon. Sure, you could actually swallow as much fluid as you sweat out and as much carbohydrate as you burn, but it would only come back up the way it went down, slightly warmer.
According to Christine Rosenbloom, Ph.D., and a nutritionist at Georgia State University, however, "There are huge variations in the amount of fluid consumption individual runners can tolerate and in the amount of carbohydrate they can absorb while running." And you cannot know how much your body is able to handle—thus you can’t be certain you’re consuming the right amount of nutrition in your next marathon—unless you make the effort to discover it in your training. Also, as with every other aspect of running, practice helps. "By routinely trying to take in more nutrition in training runs and perhaps also in the occasional shorter race, you can learn to tolerate more than you could right now," says Rosenbloom. For these two reasons, "training your gut" is essential for optimal marathon performance.
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The first thing you need to do is to start thinking about your bolus. That’s right, your bolus. It’s a funny name for the contents of your stomach. The reason it’s important is that, up to a point, the greater the volume of nutrition in your stomach, the faster it empties. And the faster your stomach empties, the faster the needed fluids and carbohydrate get into your bloodstream. So it’s a good idea to practice beginning your workouts with a larger bolus than you’re used to having.
It should be mostly sports drink. Liquids empty from the stomach faster than solids and sports drinks are absorbed through the intestine faster than other liquids. A good sports drink is also formulated to contain only what working muscles need and nothing extra. Drink between 60 and 30 minutes before your workouts—especially your longer and harder runs—and again five minutes before starting. Try to urinate within 10 minutes of starting so that you don’t get the urge during the workout. Begin with a modest amount. Even a few ounces may feel uncomfortable at first, if you’re used to running on an empty stomach, but keep doing it and you should adjust. When you do, try drinking a little more before running, and continue in this way until you’re confident you’ve found your personal limit.
Don’t use just any sports drink. In at least half your workouts, use the drink that will be offered at aid stations in the marathon you’re training for. If either your tongue or your stomach does not like this drink, or if the drink is poorly formulated (more on this in a moment), use a second sports drink of your choice in up to half your workouts.
According to Edmund Burke, Ph.D., and author of the book Optimal Muscle Performance and Recovery, you should avoid using sports drinks that contain fewer than 20 grams of carbohydrate per 12 ounces, unless you have a very sensitive stomach. Avoid using sports drinks that contain more than 30 grams of carbohydrate per 12 ounces even if your stomach is cast iron, because such concentrated drinks absorb too slowly. Burke also advises staying away from sports drinks whose primary carbohydrate ingredient is fructose, which is digested more slowly than sucrose, glucose and maltodextrin and is more likely to cause stomach cramping. Be sure to use a drink that contains the electrolytes sodium (100 to 200 mg per 12 ounces), potassium (100 to 150 mg per 12 ounces), and magnesium (30 to 70 mg per 12 ounces). And lastly, avoid using sports drinks that contain "marketing ingredients" like ginseng and chondroitin that cannot in any way fuel working muscles.
Carry or give yourself access to your sports drink on all of your long runs and marathon-pace workouts. Again, in your early workouts, drink only a small amount that you know you can handle. In subsequent workouts, gradually increase your intake until you reach the limit of your tolerance, keeping in mind that it may take your body a few tries to get comfortable with any given intake level. Increase your intake by drinking more frequently, then work on drinking larger amounts at a time so that you will maintain a larger bolus. Don’t drink more often than once a mile, though, because you want to simulate the feeding schedule provided by marathon aid stations.
In your early workouts you should test different brands and flavors of sports drink, assuming you’re not a big fan of the marathon’s drink choice. Start with a drink that’s heavier in carbohydrate content; if it works well, use it, or another drink containing a similar amount of carbohydrate. If it causes problems, go to a less concentrated drink. If you can tolerate a more concentrated drink, says Burke, consider testing out a sports drink that contains a small amount of protein in addition to carbohydrate. Such drinks may reduce the amount of muscle protein breakdown you experience during long workouts, so that you recover more quickly afterward.
How to Increase Mileage Running
In order to create your optimal marathon nutrition strategy, you just need to know the maximum volume of sports drink consumption you can tolerate before running and the maximum rate of consumption you can tolerate while running. Having determined these numbers in your training, simply duplicate them before and during your race, making sure to drink between 60 and 30 minutes, and again five minutes before the start, and at every aid station, if possible.
Now, of course, you won’t be handed measured amounts of sports drink at aid stations so you’ll have to control your intake by gulp size. In some cases you may need to drink only a portion of the contents of a cup you’re given. If you have a high tolerance and are given a small portion, you may need to take more than one cup at some stations.
Have confidence in the gut training you’ve done and stick to the plan that’s come out of it. Then, during the second half of the marathon, enjoy passing runners who didn’t train their guts.
