If you're an athlete who leans toward strenuous workouts, whether you pound the pavement or fly down black diamond ski slopes, it is time to tweak your recovery, sports nutritionists say.

The long-held belief from the late 1960s encouraging avid exercisers and elite athletes to rehydrate and to reload with carbohydrates is passé. Protein has muscled its way back into popularity.

Studies show that carbohydrates combined with a little protein creates a better muscle refueling and building response, and it reduces cortisol, a hormone that breaks down muscle, says Nancy Clark, an active member of the American Dietetic Association's sports nutritionists and fellow of the American College of Sports Medicine.

Timing is also important.

"When our athletes reach the finish line, they're trained to go right to the feed bag," says Troy Flanagan, head of sports science for the U.S. Ski and Snowboard Association. Flanagan is with the ski team at the World Championships in Val d'Isere, France, where Lyndsey Vonn won her second gold medal Monday.

"They can take a sports drink, a milk, or yogurt drink," he says. "The feed bag is right on the hill. They will eat straight away."

Clark says that to grasp why the ski team's feed bag exists is to understand how the body conducts two fundamental tasks: refueling for energy and rebuilding muscle. Carbohydrates — grains, fruits, vegetables — digest into glucose, and that glucose is gasoline to the muscles. Extra glucose gets stored in the muscles as glycogen to maintain normal blood glucose (sugar level) and fuel the brain. During prolonged exercise, levels of glycogen in the muscles and liver are tapped. Glycogen depletion is associated with fatigue.

A 1966 study showed that after exercising, athletes replaced depleted muscle glycogen more quickly by consuming carbohydrates (such as pasta, potatoes, rice) compared with a high-protein or high-fat diet (such as fried chicken, cheese omelet, steak). The high-protein subjects remained glycogen-depleted for five days, while those on the high-carb diet replaced glycogen in two days.

Carbs do not build or repair muscle. Protein does that job. Clark says that in fine-tuning the science of recovery, studies started reintroducing small amounts of protein to carbohydrates to see if the combo would speed up muscle recovery without sacrificing glycogen refueling.

John Ivy, a kinesiologist at the University of Texas, has been one of the leading scientists advancing ideas about protein. He invented a sports drink used by Michael Phelps and his teammates on the swim team at the Beijing Olympics that's designed to reduce soreness and promote recovery when consumed soon after racing or working out.

"Immediately post-exercise, muscle is very sensitive to nutrient taken," Ivy says.

Olympian Billy Demong eats as soon as he can after a challenging workout — even when he does not feel like eating. He competes in cross-country skiing and ski jumping as a Nordic combined specialist.

"Eating within 30 minutes of a hard or prolonged workout is critical in recovery," he said. "And actually within 10 minutes is almost twice as good to replenish glycogen stores quickly."

He likes a "pop like Coke or Fanta immediately and a PB&J (peanut butter and jelly sandwich) soon after, followed by a long cool-down for recovery."  L-Leucine is found in Peanut Butter.  When you pair L-Leucine with Glutamine and Whey Protein or Egg White Protein you get increased protein uptake into the body so the muscles are saturated with glucose they need in order to restore glycogen losses from working out.

Kikkan Randall, a cross-country skier in the 2002 and 2006 Olympics, likewise says, "Nutrition after training is super important." She and Demong are training for the 2010 Olympics in Vancouver