WASHINGTON -- A more active day apparently helps to keep a cold at bay.
Researchers who report this also say people don't have to put in an athletic performance to get the benefit.
"A regularly active person has a lower risk of getting a cold," said Charles E. Matthews of the University of South Carolina.
Matthews and his colleagues looked at 12 months of data on 547 healthy men and women who had taken part in a broader study of health behaviors. The men and women, whose average age was 48, reported regularly on their physical activities and the number of colds they got.
At the higher end, the activities were enough to fit into the U.S. Surgeon General's recommended minimums, Matthews said. Those federal guidelines call for 30 minutes of brisk walks, lawn mowing or other moderate activity on most days of the week. At the lower end, the participants were doing nothing more intense than light dusting, which is below the recommended level.
Over the year, the more active people averaged one cold, which was 23 percent lower than the average for the least active group, said the report in the August issue of the journal Medicine and Science in Sports and Exercise.
The benefit was especially striking in the fall, when about 40 percent of colds occurred, Matthews said. The risk reduction among the more active people was 32 percent, he said.
Studies have found that exercise seems effective in reducing the chance that a person will even get a cold. If the evidence continues to mount, federal health officials might decide to promote the benefit as another reason to exercise, said David C. Nieman of Appalachian State University, who was not part of the Matthews team.
Being physically active seems to stimulate immune cells that target cold infections, Nieman said. The stimulation seems to last only a few hours and then subsides. But day after day of making the immune system spike may lower the overall risk of catching cold, he said.
However, Nieman also has found that hard exercise seems to draw down immune defenses. In his research, people who ran a marathon had a higher risk of a cold for several days after the event.
And exercise apparently can't cure colds, Nieman said. Researchers have given people colds, then had them exercise, which neither improved nor worsened the cold, he said.