According to a recent research, daily moderate exercise helps in keeping colds at bay.
This study published in the November issue of the American Journal of Medicine reports that there was 50% reduction in the number of attacks of cold in older women who walked for half-an-hour daily for one year when compared to those who did not exercise.
"There's been a lot of anecdotal evidence that exercise prevents infection, and colds in particular," said the study's lead author, Cornelia M. Ulrich, an associate member of the Fred Hutchinson Cancer Research Center in Seattle.
"Our team's study is the first randomized clinical trial to look at the impact of moderate physical activity on the actual number of colds contracted, " she said.
The study involved assessment of 115 overweight women based in Seattle area who had previously not been doing any regular exercise and all were past menopause of an average age of 61 years.
They were divided into 2 groups, the exercise group and the control group. 53 of them were allocated to the first group, where they performed moderate exercises like brisk walking for half-an-hour, 5 days a week. While the other 62 in the control group went for a 45-minute stretching class only once a week.
There was no change in the dietary habits of the participants. Data concerning cold symptoms or other upper respiratory infections were collected every 3 months in the form of a questionnaire.
"Overall, the non-exercisers got two times the number of colds," Ulrich said.
"The benefit of exercise in reducing colds was even greater in the final three months of the study, " she added.
"In the final three months, one of 10 exercisers had a cold, but one of three of the non-exercisers did," Ulrich noted. "Couch potato" types, "were more than three times as likely to get a cold," she said.
Ulrich also said, "There was no overall difference in the risk of upper respiratory infections (like flu) between groups, but this could be due to the fact that more non-exercisers had received the flu vaccine. "
42% of the participants in the control group had been vaccinated against flu while only 23% in the exercise group were vaccinated.
How exercise controls colds is yet to be found out.
"We think there are [positive] changes in the immune system," Ulrich said.
"The study results make sense", said David Nieman, a professor of health and exercise science at Appalachian State University, Boone, N.C., and a veteran researcher of the exercise/colds link.
In a study conducted by him, there was 50% reduction in the number of days of cold symptoms in the exercisers when compared to the non-exercisers.
"The new study adds more valuable information to the mix", he said.
"I think it is another set of data that now adds to the growing awareness that one of the most powerful ways of keeping your sick days down is to do nearly daily [physical] activity," Nieman said.
Neiman said that each session of moderate exercise brought about positive immune changes, in a report on exercise immunology, published in 2003 in Current Sports Medicine Reports.
"Over time, this translates to fewer sick days from colds or flu, " he said.
"But the new study does have some potential weaknesses, " added Dr. Paul D. Thompson, director of cardiology at Hartford Hospital who co-authored an editorial that accompanied the journal report.
"Infections were self-reported, colds were reduced [in the exercisers], but there was not a reduction in upper respiratory infections [overall]," he said. "Could subjects have 'reclassified?'"
"In other words, they may have described a cold as the flu, " he said.
He also said, "The control stretching group worked in close proximity during the 45-minute sessions, which could have left them more vulnerable to catching and spreading infection than the more-solitary walkers. "
"Even so, the new study suggests there's yet another good reason to exercise, " he said.
Thompson said, "Regular physical activity probably reduces the chance of colds, probably reduces the incidence of heart attacks and heart disease, helps prevent diabetes, helps control body weight and keeps you out of the nursing home."