If your weight, health and overall quality of life weren't reason enough to get active on a regular basis, here's another one that might get you off the couch: Working out can help you fight the flu this winter season. Well, that's according to a study on mice anyway. Researchers from Iowa State University have found that mice who regularly run on a treadmill experience flu symptoms that are far less severe than the symptoms suffered by their lazier counterparts. Even mice who only started exercising right before the flu had less severe symptoms, though the ones who were regular gym-rats (pardon the pun) had longer-lasting positive effects -- meaning their symptoms were diminished throughout the course of their illness, not just in the first few days.

The findings, published in the Journal of Infectious Diseases, suggest that exercise can really boost the immune system, and while it's not clear whether the results can be applied to humans as well, researchers are optimistic. And besides, it's already the general consensus that regular, moderate exercise helps improve your odds against illness.

Still, don't overdo it -- you can get too much of a good thing. According to Jeffrey A. Woods, a professor of kinesiology and community health at the University of Illinois, prolonged and intense exercise sessions can lead "to increased susceptibility to viral infection." His advice on navigating flu season? "I would recommend everyone get the annual influenza vaccination and the new H1N1 vaccination," he tells The New York Times.

The flu isn't the only thing that exercise is good for -- cardio is more effective than heart surgery.