Exercise linked to fewer, milder colds

Physical fitness and frequent aerobic activity reduced upper respiratory tract infections.

High perceived physical fitness and nearly daily aerobic activity were associated with reduced upper respiratory tract infection frequency, severity and symptomatology.

Findings from previous epidemiologic reports have retrospectively or prospectively examined the incidence of upper respiratory tract infections in moderately active and sedentary individuals.

The findings support decreased rates of upper respiratory tract infections in physically active groups. The primary criticism of these findings, however, is that upper respiratory tract infection incidence and symptomatology were not measured with validated methods in any of these studies.

“The physically active always brag that they’re sick less than sedentary people,” David C. Nieman, DrPH, director of the Human Performance Laboratory at Appalachian State University, in Kannapolis, N.C., said in a press release. “Indeed, this boast of active people that they are sick less often is really true.”

To investigate the relationship between physical activities with upper respiratory tract infections during a 12-week period, researchers followed 1,002 adults during the winter and fall seasons of 2008.

They monitored symptoms and severity using the Wisconsin Upper Respiratory Symptom Survey, a daily logging system designed and developed to comprehensively measure significant health-related dimensions that are negatively affected by the common cold.

During the 12-week period, the total number of days with upper respiratory tract infection was reduced by 43% in those reporting at least 5 days per week aerobic exercise compared with those who were largely sedentary (≤1 day per week aerobic exercise). When comparing those in high vs. low physical fitness tertiles, the number of days with upper respiratory tract infection was reduced by 46%.

For severity of upper respiratory tract infection, high perceived physical fitness was correlated with a 32% reduction, and near-daily aerobic activity was correlated with a 41% reduction.

For symptomatology of upper respiratory tract infection, high perceived physical fitness was associated with a 34% reduction, and near-daily aerobic activity was associated with a 41% reduction.

Factors, including older age, high or medium fitness level, lower education, being married or male, and eating at least three servings of fruit per day, were associated with an adjusted mean of five or fewer days with upper respiratory tract infection.

Exercise activates the immune system at a higher rate than normal and causes immune cells to attack viruses, according to Nieman.

“Exercise gets these cells circulating around the body,” he said. “Any aerobic exercise should give you these immune benefits.”

The underlying mechanisms for the reduction in upper respiratory tract infection risk with aerobic exercise training are still being explored and debated, according to the researchers.

Example of more info:

For more information:

• Nieman DC. Br J Sports Med. 2010;doi:10.1136/bjsm.2010.077875.

It would be comforting to say that the main message of this paper is true: Exercise and good physical fitness reduce the number and severity of upper respiratory infections. However, there are some potential problems with this study. First is that physical fitness was determined by a questionnaire and not by objective measure. The only measured criterion was BMI, and it is of interest that those reporting higher physical fitness had a lower BMI. Also, it was not possible to test the hypothesis that those with a "healthier" lifestyle make a choice to engage in exercise more frequently. Finally, the proposed mechanism is that aerobic exercise causes enhanced immune function. The problem with this construct is that vigorous immune response to viruses is likely the cause of upper respiratory infection misery.

– Robert S. Baltimore, MD
Infectious Diseases in Children Editorial Board

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