 -- Tens of thousands of runners will line up in Staten Island to run the TCS New York City Marathon this Sunday. Preparing properly for a marathon can take weeks to months and require runs that span hours. But on race day plenty of new and even experienced runners can get caught up in common preparation myths that have little science to back them up.

We talked to some sports medicine and marathon experts to find out which common running tips are myths and which have scientific evidence to back them up.

MYTH: Carb Loading Is Absolutely Essential to Running Fast

Robert Truax, an osteopath and sports medicine specialist at the University Hospital Cleveland Medical Center, said experts now advise simply eating enough before a race. It's not necessary to inhale a box of pasta to have a good long run.

"What matters is that you have the calories," he said. "What you're eating the night before and the diet you eat is critical if you're trying to win the Olympics. But if you're trying to complete the marathon ... your training is the most important."

MYTH: A Long Stretch Will Keep You Injury-Free

Stretching may seem an essential part of any workout, but the experts say there's not a lot of evidence that it keeps people injury free.

Dr. Dennis Cardone, the chief of primary care sports medicine at the department of Orthopedic Surgery at NYU Langone Medical Center, said studies have shown a good stretch doesn't translate into a better or safe run.

"They should just do some type of warm-up," he said of marathon runners. "It's not so much about the stretching."

John Honerkamp, a coach for the New York Road Runners, said he sometimes stretches to get the circulation going, but he warned, "If you go out on long [training runs] and don't stretch, don't do that that on race day."

He pointed out that the first mile of the race, on the Verrazano-Narrows Bridge, is the steepest, so runners can warm up the first few miles before switching to a faster pace.

"If you're trying to run three or four hours ... you don't want to get your pace right away," Honerkamp told ABC News.

MYTH: Eat a Bunch of Unfamiliar Sports Bars/Goo/Gummies During the Race

While experts advise having some kind of calorie replacement every hour during a long run, they advise against eating a bunch of unfamiliar food, including products like goo, gummies or bars.

It's wise to go easy on sports goo, designed to be easily eaten during long runs, Cardone said.

"The general recommendation is just one during the marathon. It's big carbo load and can affect your stomach," he said.

He pointed out that the top rule for marathon runners is to avoid doing anything different on race day from how they train. This means avoiding any free sports treats from the marathon expo unless they were already incorporated into your training.

MYTH: Drink at Every Water Station

While health experts used to think that runners should stay so hydrated that they never felt thirsty, that advice has changed, Cardone said. Instead, he advises runners to wait until they feel thirsty before taking a drink.

"One of the biggest problems is hyponatremia ... a decrease in sodium in body," he said.

Slower runners can end up drinking too much water, which can decrease the sodium concentration in the body — a potentially dangerous condition if the level drops too low.

"We've gone full circle to 'Don't overhydrate.' That's more dangerous than being underhydrated," Cardone said.

MYTH: Compression Clothing Will Help You Run Faster

There is no item of clothing that is going to allow you to magically run faster, experts noted.

However, even though compression clothing can't help runners finish the race faster, it may help with a post-run issue called venous pooling, in which blood accumulates in the legs, according to Cardone.

"They might get a little lightheaded and get swelling in their ankles" because of the pooling, he said. "The compression clothing ... can maybe help some of that pooling."

This means runners might want to keep compression socks on after the race rather than take them off as soon as they cross the finish line, he said, adding that if they haven't been training in compression, race day is not the time to start.

FACT: Beer Can Help Relieve Aches and Pains

Here's a fact that may make many people rejoice: Beer (in moderation) can act as a muscle relaxer to help diminish the pain of a long run.

Marathoners often celebrate the end of a race with a cold pint, even if it's still morning. This tradition can help runners recover, Truax noted.

"Depending on what beer you're getting, there's a carbohydrate load, and the oldest muscle relaxer in the world ... is alcohol," he said.