Matt Fitzgerald—When Meb Keflezighi and Ryan Hall reached the 23-mile mark of the 2012 U.S. Olympic Trials Marathon as co-leaders of the race, they were on pace to finish in 2:08:34. Keflezighi wound up stopping the clock at 2:09:08, Hall in 2:09:30. In other words, both runners hit a wall—not catastrophically, but enough to have felt it.
The third man to reach the 23-mile mark, Abdi Abdirahman, also slowed down over the last 3.2 miles of the race, as did the fourth- and fifth-place finishers. In fact, you have to go all the way back to 12th place to find a runner—Ricky Flynn—who held pace over the final 5K of the Olympic Trials marathon.
Yes, pro runners hit that imaginary but very real physiological wall, too, but it’s not nearly the problem that it is for the rest of us. Roughly three out of every four participants in any given marathon cover the second half of the race at least two minutes slower than the first. Many runners slow down even more dramatically after the 20-mile mark, where the wall traditionally hovers. By contrast, less than one in 10 half-marathon participants slow down by a comparable amount, and in races shorter than 13.1 miles hitting the wall is a rare occurrence.
The most common cause of hitting the wall is muscle glycogen depletion. Glycogen, a fuel derived from dietary carbohydrates, is stored in relatively small amounts in the muscles and liver, where it waits to be delivered to muscles via the bloodstream in the form of glucose. Most runners have enough glycogen in their bodies to run 13.1 miles at a good pace. But the marathon is fundamentally a metabolic challenge. If you run the first half of the race even one percent too fast, you risk depleting your glycogen levels. Finishing a marathon without hitting the wall requires storing and conserving enough glycogen fuel to avoid running out of it somewhere between 20 and 26 miles—which, as the statistics show, is not easy to do.
Good pacing is paramount. You’ll burn through precious glycogen stores more slowly if you maintain a consistent pace than you will if your pace is erratic, even if it averages out to be the same. Proper training also helps. A good marathon training plan will increase your capacity to store glycogen and improve your running economy and fat-burning capacity, enabling you to burn through stores at a slower rate.
But pacing and training aren’t enough. You must also maintain an appropriate nutrition plan throughout your training process. However, the thinking behind marathon (and half-marathon) training nutrition has shifted in recent years. Follow these six rules to maximize your training and avoid the wall in long-distance races.
Old Rule: Runners don’t rely as much as non-athletes on diet for weight management.
New Rule: Runners rely more than non-athletes on diet for weight management.
Until recently, exercise scientists believed that variables such as VO2max (or aerobic capacity) and running economy were the most powerful predictors of running performance. But recent research has revealed that body composition is equally important. One study involving elite Ethiopian runners found that those with the least body fat had the fastest race times.
Each runner’s optimal racing weight falls near the bottom end of his or her healthy weight range because excess body fat is dead weight that increases the energy cost of running. A typical runner who sheds just one pound of body fat could see a one-minute improvement in his or her marathon time without any change in fitness.
The runner’s goal of reaching his or her ideal racing weight is more challenging than the average non-runner’s goal of staying within his or her healthy weight range. To reach racing weight, runners have to eat more carefully than non-runners must eat to avoid becoming overweight.
Complicating matters for runners is something called the compensation effect. The more a person exercises, the more his or her appetite increases and the more he or she eats. Simply ignoring the increased appetite is not a viable solution, but neither is an extra-large, double-cheese pizza.
Instead, runners must increase the quality of their diets. High-quality foods such as vegetables are less calorically dense than low-quality foods, satisfying the appetite with fewer calories. The six high-quality food types are vegetables, fruits, nuts and seeds, whole grains, lean meats and fish, and dairy. And the four basic categories of low-quality foods are refined grains, fatty meats, sweets and fried foods.
Take-Away Tip: When training for a marathon, fuel with high-quality foods to reach the starting line lighter. Muscles burn less glycogen at goal pace, meaning you’re less likely to hit the wall.
Old Rule: The high-carb diet recommended to runners in the 20th Century was a mistake.
New Rule: The current carbohydrate-moderation fad in running is a mistake.
Back in the 1960s, Swedish researchers discovered a high-carbohydrate diet increased muscle glycogen stores and thereby boosted endurance running performance. The practice of pre-marathon “carbo loading” was born out of this research. Subsequent studies revealed a high-carbohydrate diet also increased runners’ capacity to absorb heavy training loads day after day. Sports nutritionists have recommended high-carb diets for runners ever since.
Well, most sports nutritionists recommended high-carb diets for runners almost ever since. Lately, some experts have suggested a low-carb diet is better, arguing when runners maintain a low-carb diet their muscles become better fat burners, an adaptation that spares muscle glycogen in marathons and thereby pushes back the wall.
Studies have shown that low-carb diets do indeed increase fat burning during running. However, this effect has not been linked to improved endurance performance. Meanwhile, new research has reconfirmed that runners aren’t able to train as hard on a low-carb diet because it produces chronically low glycogen stores.
A study conducted by Asker Jeukendrup and colleagues at the University of Birmingham, England, compared the effects of a 41 percent carbohydrate diet and a 65 percent carbohydrate diet during an 11-day period of intensified run training. On the low-carb diet, performance levels decreased and the runners’ self-reported fatigue levels increased. On the high-carb diet, performance and energy levels were maintained.
Take-Away Tip: The amount of carbohydrate a runner needs to handle his or her training is tied to the amount of training he or she does. Use this table to determine how much carbohydrate to include in your diet.
|Average Daily Training Time(Running and Other Activities)||Daily Carbohydrate Target|
|30-45 minutes||3-4 g/kg|
|45-60 minutes||4-5 g/kg|
|61-75 minutes||5-6 g/kg|
|76-90 minutes||6-7 g/kg|
|90 minutes||7-8 g/kg|
|>120 minutes||8-10 g/kg|
Old Rule: Drink plenty of sports drink every run to boost performance.
New Rule: Do some “fasting workouts” to make muscles better fat burners.
Sports drinks aid running performance by limiting dehydration and supplying muscles with an extra source of energy. But you do not need a sports drink on every training run. Research has shown that sports drinks have no effect on performance in hard runs lasting less than one hour or easier runs lasting fewer than 90 minutes.
What’s more, other studies suggest the carbohydrates in sports drinks act as a physiological crutch by limiting some beneficial fitness adaptations that occur in response to training. Improvements in the muscles’ fat-burning capacity and other adaptations depend partly on the depletion of muscle glycogen stores during workouts. Sports drinks attenuate glycogen depletion and thereby blunt the body’s adaptive response to the run. Sports drinks are imperative for longer and harder workouts, but relying too heavily on them in training may make you less fit.
Take-Away Tip: Use a sports drink during roughly half of your runs lasting between one and two hours and during all of your runs lasting longer than two hours.
Carbo- and Fat-Loading
Old Rule: Carbo load before a race.
New Rule: Fat load, then carbo load before a race.
Earlier I said a low-carb diet—specifically a high-fat, low-carb diet—increases fat burn during running, but this benefit comes at the cost of reduced training capacity. For this reason, it’s not recommended runners use such a diet as their normal training diet. However, research has shown that a short-term, high-fat diet that immediately precedes the traditional pre-race carbo load offers the best of both worlds. 10 days of fat-loading are enough to increase the muscles’ fat-burning capacity, while the subsequent three-day carbo load ensures muscles also have plenty of glycogen available.
In 2001, Vicki Lambert, an exercise scientist at the University of Cape Town, South Africa, tested the effects of 10 days of fat loading followed by three days of carbo loading on endurance performance in cyclists. After warming up with two hours of moderate-intensity cycling, Lambert’s subjects were able to complete a 20K time trial 4.5 percent faster after using this protocol than they did when carb loading was preceded by their normal diet.
To get these benefits in your next marathon you’ll have to get 65 percent of your calories from fat every day for ten days starting two weeks before your race. This means virtually everything you eat will need to be high in healthy fats. Recommended staples for fat loading are avocadoes, Greek yogurt, cheese, eggs, nuts, olives and olive oil, salmon, and whole milk.
Take-Away Tip: Switch from fat-loading to carbo-loading three days before your marathon. Aim to get 70 percent of your total calories from carbs during this period.
Drink Beet Juice
Old Rule: Drink plenty of water before your marathon.
New Rule: Drink plenty of water and a little beet juice before your marathon.
Every runner knows it’s important to hydrate before the start of a marathon, but it’s easy to go overboard. You don’t have to drink a lot to achieve full hydration after a night of sleep, and any excess will only force you to wait in long toilet lines before the start and—worse—stop for bathroom breaks during your marathon. Limit morning of, pre-marathon fluid intake to 24 ounces and don’t drink anything in the final hour before the race begins.
Here’s another suggestion: Instead of drinking water before your marathon, drink beet juice. Why? Beet juice is packed with dietary nitrates, which help blood vessels dilate, increasing blood flow to muscles during exercise. Studies have shown that drinking half a liter (about 17 ounces) of beet juice two to three hours before running can enhance performance.
Take-Away Tip: See if beet juice helps you by testing it before some practice runs. A word of caution: Don’t try it for the first time on the morning of a marathon.
Old Rule: Drink as much as you can during the marathon.
New Rule: Drink by thirst.
If you’ve been a runner longer than a week you’ve probably been advised at least once—perhaps dozens of times—to hydrate during your race with a sports drink at a rate sufficient to offset weight loss from sweating and to provide 60 grams of carbohydrate per hour. The rationale behind these recommendations is that full rehydration elevates performance by aiding thermoregulation and reducing cardiac strain, while absorbing carbs at the highest possible rate enhances performance by maintaining blood glucose levels and delaying muscle glycogen depletion.
Lately, however, these longstanding guidelines have been challenged by studies indicating that, during running, such high rates of fueling cause gastrointestinal discomfort and offer no performance benefit compared to simply drinking by thirst. A new study conducted by Ian Rollo and colleagues at England’s Loughborough University, published in the International Journal of Sport Nutrition and Exercise Metabolism, provides the strongest support yet for this new “obey your thirst” philosophy.
Nine experienced recreational runners participated in the experiment. Each completed a 10-mile road race on three separate occasions, drinking nothing during one race, drinking a carbohydrate-electrolyte sports drink by thirst during another race (which came to an average of 315 ml per hour), and drinking at a prescribed rate aimed to provide the recommended 60 grams of carbs per hour in the third race (which came to 1,055 ml per hour).
In addition to timing the three races, Dr. Rollo’s team took measurements of dehydration, core body temperature, and gastrointestinal distress. Performances in the no-drinking and prescribed-drinking trials were almost identical. But, when allowed to drink according to their thirst, the runners covered the 10-mile course almost a minute faster on average.
Rollo says that further research is needed to determine why the runners performed better with intuitive drinking, despite becoming significantly more dehydrated and taking in 70 percent less carbohydrates compared to the prescribed-drinking trial. One possible explanation is suggested by the runners’ subjective ratings of gastrointestinal discomfort, which were significantly higher throughout the second half of the 10-mile race in which they were required to drink more than desired.
Take-Away Tip: Drinking a calculated amount of sports drink during a marathon is difficult. Who knows how many ounces will be in that next Dixie cup? Fortunately, you don’t have to drink according to any mathematical formula. Listen to your body to take on only as much as you need.
This piece first appeared in the March 2013 issue of Competitor magazine.
About The Author:
Matt Fitzgerald is the author of numerous books, including Racing Weight: How To Get Lean For Peak Performance (VeloPress, 2012) and The New Rules of Marathon & Half-Marathon Nutrition (Lifelong Books, 2013). He is also a Training Intelligence Specialist for PEAR Sports. To learn more about Matt visitwww.mattfitzgerald.org.