Exercise Can Help Fight Flu

Worried about not being able to get a flu vaccine this year? Exercise may be the flu remedy you've been looking for.

Moderate exercise helped mice survive the flu in a recent lab test done by researchers at University of Illinois at Urbana-Champaign. They presented their findings at the 2004 American Physiological Society Intersociety Meeting in Austin, Texas.

After exposing mice to the flu virus, Jeffrey Woods, PhD, and colleagues randomly assigned some rodents to a four-day workout program with 20-30 minute daily exercise sessions. The mice stopped exercising when flu symptoms appeared, simulating typical human behavior.

For comparison, another group of flu-exposed mice didn't exercise at all.

The exercising mice were twice as likely to survive the flu as the sedentary group: 59 percent of exercising mice survived the flu, compared with 29 percent of those that did not exercise.

Mature exercisers (age 20 weeks) fared best. Eighteen out of 22 mature exercising mice survived the flu, compared with only 10 out of 22 sedentary mice of the same age. The protective benefit of exercise wasn't seen in younger mice aged 11-16 weeks.

It's worth noting that the mice weren't hard-core rodent "athletes." They only exercised moderately for a handful of days; none exercised regularly before the experiment.

"Our work has shown that moderate exercise for four consecutive days post-infection significantly increased survivability to influenza infection," write the researchers.

They plan to do follow-up studies with animals that had been exercising regularly, according to a news release.

The researchers also want to learn how exercise exerts its protective effect against the flu.

Meanwhile, a large clinical trial with human participants is underway at the University of Illinois' physical fitness laboratory, examining whether moderate exercise training can boost immunity (including responses to flu vaccine) in older adults, according to a news release.

By Miranda Hitti; reviewed by Michael W. Smith, MD

SOURCES: 2004 American Physiological Society Intersociety Meeting, "The Integrative Biology of Exercise," Austin, Texas, Oct. 6-9, 2004.  News release, American Physiological Society.