BOSTON, Oct. 22 (UPI) -- A Boston medical student says his model helps marathon runners avoid "hitting the wall," a physical limit caused by a lack of carbohydrates.
Benjamin Rapoport, a medical student and doctoral student at Harvard and the Massachusetts of Technology, says several miles before he ended the New York marathon, his legs just didn't want to keep up the pace -- essentially, the body runs out of fuel, forcing the runner to slow down dramatically.
"You feel like you're not going anywhere," Rapoport says in a statement. "It's a big psychological letdown, because you feel powerless. You can't will yourself to run any faster."
Hitting the wall occurs when the body's carbohydrates -- stored in the liver, leg muscles and blood -- are completely depleted, forcing the body to start burning fat. The by-products of fat metabolism start building up, causing pain and fatigue.
The model allows runners to calculate their aerobic capacity and how much carbohydrates they need to eat during the race.
For example, a runner who wants to achieve the 3-hour, 10-minute Boston Marathon qualifying time would need to consume about 700 calories -- for a 154-pound runner -- assuming his legs make up at least 15 percent of his body mass, Rapoport says.