Fall marathon season also happens to coincide with the release of the seasonal flu vaccine. While offices, pharmacies and schools around the country are offering up the vaccine, many runners, concerned about whether the shot will negatively impact their performance, are questioning whether they should join the masses and line up for the shot.

I understand the concern. I shied away from the vaccine in the week leading up to running a marathon because I worried that a sore arm wouldn't be conducive to a strong running performance. But I've heard from runners who have also avoided the vaccine over fears that it might leave them feeling sluggish, tired or sick.

"This whole idea that you can get sick from the vaccine is just not true," says Dr. Robert Sallis, director of sports medicine at Kaiser Permanente Fontana and past president of the American College of Sports Medicine. "It's an inactivated virus," he says, so getting the flu from the shot is not possible. Furthermore, he adds, "The vaccine should have absolutely no effect on running performance." A severe allergic reaction resulting from the vaccine is extremely rare. Most people can expect soreness, bleeding and pain at the injection site that should dissipate in a few days. So it's probably a good idea not to get the shot in the few days before running a race. "But there's no reason the vaccine should make you tired or sluggish," he says.

Another issue concerns the timing of getting the vaccine. Should you get the shot before a race or hold off until marathon day is behind you? "I see no reason to wait unless you have a history of reaction to the vaccine," Sallis says. In fact, he believes that if anyone should be lining up for a flu shot, it's runners who will typically be milling around large groups of people at races where there is little or no access to running water to wash hands -- one of the first line of defenses in preventing flu.

To further complicate things, distance running can make you more susceptible to colds and flu. "We know that for a few weeks after running a marathon your resistance is low, making getting the flu vaccine before the race even more important," Sallis says. Keep in mind, however, that it takes about two weeks after you receive the vaccine to be fully protected against the flu.

While the vaccine is considered the best way to avoid the flu, hand washing, eating right and sleeping enough will also help keep your immunity high. And, of course, running helps, too.

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