Fuel For The Fire Inside

Just like a car, your body needs fuel to keep it going. But not just any fuel will do, especially if you want to push your body to extremes of speed and endurance. You don't think they put regular unleaded in Indy cars, do you? So why dump processed junk willy-nilly into your engine? To properly fuel up, it's important to know that certain types of nutrients burn at different rates and help your body with different tasks before, during and after you exercise.

Scott Jurek, the world's most acclaimed ultramarathon runner, has his food intake down to a science. His food fuels him on long weekend runs, which average 30 miles or more, and help him recover so he can lace up again and again.

While each person differs and requires different amounts of fuel, Jurek shared some easy formulas that'll show you know exactly how much you need.

Depending on the heat and your level of effort, you will need a different amount of water every time you exercise. According to Jurek, the general range is from 16 to 40 ounces per hour. That's a huge range, so Jurek recommends taking the "sweat test" to determine exactly how much your body requires.

To take the sweat test: 1) Weigh yourself, 2) Exercise for one hour without drinking any water or going to the bathroom, 3) Weigh yourself again to see how much weight you lost during exercise, 4) Convert that weight to ounces (there are 16 in a pound). Now you know exactly how much water you should drink for that exercise at that temperature.

But not everyone stops for water during runs and races. Jurek says it's OK to allow yourself to lose 1 to 2 percent of your body weight during a run, as long as you replenish yourself afterwards. Losing any more than 2 percent of your body weight on a run signals that you're dehydrated. When that happens, your heart rate automatically increases, making exercise more difficult.

While most nutritionists will say that Americans, as a whole, eat too much salt, sodium is key to preventing muscle cramping during exercise. When you sweat, you lose a lot of sodium through your pores, so your sodium intake should be related to how much you sweat. Jurek recommends consuming between 200 and 400 milligrams of sodium per hour.

These fast-burning nutrients are the most important to eat right before, and again during, a run. Because your body can turn carbs into energy faster than any other nutrient, you should try to take in a steady stream of them over the course of long runs.

To calculate how many carbs you should eat, convert your body weight to kilograms (one kilogram equals 2.2 pounds). Take that number and multiply it by 0.7. That is how many grams of carbs your body needs per hour of exercise. For more strenuous exercise—which Jurek defines as anything more than marathon-length—simply multiply by one.

For a 120-pound woman, the formula works as follows:
Marathon or shorter: 54.4 kg x 0.7 = 38 grams of carbs
Longer/more strenuous: 54.4 kg x 1 = 54.4 grams of carbs

Jurek says runners only need protein when their exercise lasts more than three hours. Otherwise, protein is better as a recovery nutrient. For those really long runs, he recommends consuming 10 to 15 grams of protein every two to three hours.

For recovery, he says to multiply your body weight in kilograms by 0.2 to find how many grams of protein you should eat within 30 minutes of completing a workout.

For our 120-pound woman:
54.4 kg x 0.2 = 10.9 grams of protein

Fat cannot be digested fast enough for you to consume it during a run and reap any benefits. Moreover, the fat stores that your body is already carrying will be easier to digest if your body needs them during a run. Jurek says that, for recovery, you may want to eat 3 to 5 grams of fat in the first half-hour after a run.

Now for the moment you've been waiting for—Jurek recommends a specific food. While most of these crucial nutrients are packed into easy-to-carry energy gels like GU or Clif's Shot Bloks, he prefers "real food" on long runs. Nothing is as satisfying to Scott Jurek on a day-long run over trails and mountains as a rice and bean burrito.

[Ed note: He didn't elaborate, but we're guessing that Jurek's burrito is more protein- and carb-rich than what you'd find in your garden variety Taco Bell meal.]