Could exercise fend off flu symptoms? Find out how your gym date and fitness routine could fight disease and keep you healthy.

By Heidi Pashman and Mirel Ketchiff
January 23, 2013
Photo: Halfpoint Images/Getty Images

With the raging flu epidemic this year (and every year, honestly), you may be using hand sanitizer like crazy and using paper towels to open public restroom doors. Smart strategies-now add a well-timed workout to your list of ways to stay healthy.

Turns out, there are two seriously impressive ways exercise can help you fend off the flu.

How Exercise Affects the Flu Shot

In a recent study, Iowa State University researchers gave a group of young adults the influenza vaccine and then had half of them sit for 90 minutes while the other half went for either a 90-minute jog or 90-minute bike ride post-shot. After the hour and a half, the scientists took blood samples from everyone and found that the exercisers had nearly twice the flu antibodies as those who relaxed, plus they had higher levels of cells that keep infection at bay.

Marian Kohut, Ph.D., professor of kinesiology at Iowa State who oversaw the study, told The New York Times that exercise may speed blood circulation and pump the vaccine away from the injection site to other parts of the body. It also could elevate the body's overall immune system, which, in turn, helps exaggerate the vaccination's effect. (The jury's out on whether that'll work for the nasal spray flu vaccine too.)

After performing similar studies with mice, Kohut found that 90 minutes seems to be the optimal amount of exercise. Longer workouts lead to fewer antibodies in the rodents, presumably because of a diminished immune response. (Already feeling the bug coming on? Find out exactly what to do to stop feeling like crap.)

But if you prefer strength training to cardio, it's better to hit the iron before your shot, according to a U.K. study. Researchers there found that lifting weights for 20 minutes-and specifically doing biceps curls and lateral arm raises with 85 percent of the max weight you can lift-six hours before receiving the influenza vaccine also boosted antibody levels.

To Ward Off Germs All Season

If your fitness motivation has taken a nosedive along with the temps outdoors, here's another reason to keep up the hard work: Exercising for at least two-and-a-half hours a week-about 20 minutes a day-can reduce your chances of catching the flu by 10 percent, according to a 2014 study from the London School of Hygiene and Tropical Medicine.

But just running around the block or plugging away on the treadmill isn't going to cut it. In fact, if you're serious about staying healthy, you have to really challenge yourself during your workouts, report the researchers. While vigorous exercise-which should leave you breathing hard and feeling tired-offered the health benefit in the study, moderate exercise did not. (Learn how to train using your heart rate zones for more help differentiating between the two.)

Why? The study authors say that more research is needed to confirm the findings, but other studies have shown that working out seems to improve immunity. (See: How to Avoid Getting Sick During Cold and Flu Season.) It's possible that physical activity helps expel bacteria from the lungs, or that the rise in body temperature may help kill off infectious bugs. Also, the connection between high-intensity interval training (HIIT) and protection from disease has been noted before. Working out harder (not longer) appears to have an entirely different effect on the body. And some researchers believe that there is a certain threshold you need to pass in order to see changes, which could explain why a more intense sweat sesh could work toward keeping you disease-free while keeping it low key doesn't do much. (That said, any workout is better than no workout.)

Just note: If you mostly work out indoors (hello, cold weather!), you may want to take extra precautions. Gyms are notoriously rife with germs thanks to the close quarters and sweaty inhabitants, so if you're working your butt off indoors, you're not in the clear! In fact, 63 percent of gym equipment is contaminated with rhinovirus, which causes the common cold, found a study in the Clinical Journal of Sports Medicine. Plus: The free weights have even more bacteria than a toilet seat. (Eek.) Your move: Show up prepared. Bring your own towel, avoid touching your face between sets, avoid these especially germy gym areas, and wash your hands thoroughly after your sweat session to avoid getting sick.

Your Flu-fighting Plan

Reminder: If you haven't gotten your shot yet, do it. The influenza vaccination is the number one recommendation for flu prevention, according to Philip Hagen, M.D., the preventative medicine doctor and medical editor of Mayo Clinic Book of Home Remedies. (And, no, it's not too early to get the flu shot.) But since it's only 60 to 80 percent effective, schedule a strength workout before or a cardio workout after you hit the doctor's office or do an arms workout before, and you may fortify your protection. That, and keep exercising (as you already should be) on the regular. If nothing else, you'll burn calories and build muscle!