Pump up your flu shot with a trip to the gym

If you are among thousands of procrastinating Minnesotans who put off getting a flu shot until their colleagues started getting sick, an Iowa researcher may have a way to lessen your chance of catching the virus.

It's all in the wrists — and arms and abs and legs.

Turns out that moderate exercise for 90 minutes after getting your shot may nearly double the antibodies your body produces, greatly enhancing the flu vaccine.

Still, cautioned Marian Kohut, professor of kinesiology at Iowa State University in Ames, "these are very preliminary findings" with a small group.

But as the number of flu cases and deaths rises during this harsh flu season, Kohut's findings could be critically important in getting the most from annual flu shots, which health officials say are 62 percent effective on average.

Propelled by success in her earlier flu-shot research funded by the National Institutes of Health, Kohut enlisted about 18 healthy students last fall to delve deeper into how exercise affects the body's immune response to flu shots.

Half went on a moderately paced 90-minute jog or bike ride 15 minutes after receiving a flu shot. Another group of volunteers sat quietly for the 90 minutes.

Volunteers who had exercised had "nearly double the antibody response" of the less-active group, Kohut said.

In 2009, Kohut's team studied flu shot effectiveness among about 30 sedentary people 65 and older. That's a particularly important group to study because flu shots typically are less effective for older people, and they are more likely to be hospitalized or die from the flu.

For 10 months, half the older group took up regular brisk walks or a stretching routine. The active group improved their immune response somewhat, but not as much as the students in last year's research.

If 90 minutes of exercise helps that much, Kohut and her team wondered, will a longer period of exercise offer even more protection?

Not much, a group of lab mice seemed to indicate. In a subsequent study, mice that exercised for 45 minutes on a running wheel showed increased immune response, but not as much as those that ran 90 minutes. Mice that ran for up to three hours, however, had fewer antibodies.

In England, a research team tried a different approach and found that healthy adults — especially women — could improve their flu-shot effectiveness by doing biceps curls and side arm raises with heavy weights for 20 minutes before getting flu shots.

Perhaps the heavy workout inflamed the muscles where the shot was applied, thus jump-starting the immune response, researchers said. However, further testing has yielded mixed results.

"This is still a fairly new area for research, just the last 20 years," Kohut said. "We're trying to understand not only whether exercise can help make vaccines more effective, but also whether regular exercise over time makes the symptoms of flu less severe, as some of our mice seem to be telling us. What about exercising while you're ill?"

Kohut and her mice are now at work trying to answer those questions.