ATLANTA -- In the days before a big race, endurance runners customarily fuel up on pasta, bread, bagels, crackers and English muffins. "Carbs," they say, help them go the distance.
Indeed, carbohydrates -- fruits, vegetables, grains, potatoes, rice are the runner's main source of energy during a rigorous workout. The trick comes in manipulating diet and exercise so that the marathoner's energy level peaks at the starting gate.
The "carbo-loading" theory, introduced 20 years ago, has recently undergone revision.
In the week before an event such as a 10-K race, experts say, runners should generally go light on training and heavy on carbohydrates. That way the body stocks glycogen, the energy-producing byproduct of carbohydrate calories.
Heavy exercise is fine seven days before the race, but it should drop off dramatically after that, says Andrew Coggan, an exercise physiologist at Ohio State University.
Moreover, it doesn't hurt to be sedentary.
"Rest your muscles a few days before," Dr. Coggan advises.
At the same time, a moderate carbohydrate diet (one that derives half its calories from carbohydrates) is recommended. On the last two days, up those "carbs" to 70 percent, Dr. Coggan says.
The original carbo-loading routine involved moderate to intense activity during pre-race preparation. For roughly half the week, the runner avoided carbohydrates entirely. In the final three days before the race, the prescribed diet called for nothing but carbohydrates.
The starve-and-overload method was devised to trick muscles into holding their glycogen.
According to registered dietitian Missy Crawford, the approach was extreme.
"About everybody agrees that the carbohydrate-depletion phase was unnecessary, if not detrimental," says Ms. Crawford.
"It brought on physical and mental fatigue. And how you feel about your level of performance going into the race can affect how you do."