Exercise Increases Resistance to Colds

If you happen to find yourself wandering through a health food store, you’re likely to find many products claiming to be a cure for the common cold. Everything from high dose vitamin C to zinc to herbs that even doctors cannot pronounce. There is no evidence for these products actually working and with good reason. The common cold is caused by more than 200 different viruses, which makes finding a cure of vaccine incredibly elusive. This means that if a person were to find a cure for the common cold they would not only be able to retire to an island, they would be able to purchase the island. While such a cure does not exist, it turns out that a little sweat equity might boost our resistance to the common cold.

The Study

File this away in the “Medicine In Motion is not just a clever title” part of your brain because the research bears out that moderate exercise reduce the occurrence of the common cold. Researchers at Appalachian State University in North Carolina have found that regular exercise, and surprisingly the perception of being fit, are associated with a substantial reduction in upper respiratory tract infection. The study followed 1,002 adults (male & female, 18 to 85) over two 12-week periods; half participated in the fall and half in the winter. Those who said they exercised (details below) at least five days a week had 43% fewer days with upper respiratory tract infection than those who exercised no more than one day a week (4.41 days versus 8.18). Similarly, those who rated themselves as highly fit had 46% fewer days with a respiratory infection than those who reported low fitness (4.89 days versus 8.60). Even when they did get sick, frequent exercisers and the most fit suffered less severe symptoms, by 32% to 41% between high versus low exercisers and perceived fitness.

To determine high exercisers from low, participants were surveyed regarding how many days per week they exercised for at least 20 minutes, leaving them winded and sweaty. They were also asked to rate their physical fitness on a 10-point scale. They were divided into three groups (8-10 high, 6-7 middle, and 1-5 low) based on their response.

While earlier research has been performed, what set this study apart was that validated methods were used to track respiratory infections and related symptoms. The researchers chronicled the effects of the common cold using the Wisconsin Upper Respiratory Symptoms Survey, a reliable and valid daily logging system.

A Double-Edged Sword

While moderate exercise shows benefits to reducing the occurrence of the common cold, too much exercise seems to increase the occurrence. It is well-known that marathon runners often come down with colds or worst in the weeks and sometimes months after the race. This is especially true of ultra-marathoners. In a five year study of 350 athletes in the 160 kilometer Western States Endurance Run, Dr. Nieman found that one out of four runners reported sickness during the 2-week period after the race.

The effect is most certainly paradoxical. Athletes, when compared with their couch potato colleagues, experience higher rate of upper respiratory infections, especially in the few weeks following  intense training and races. In non-athletes, increasing physical activity is associated with a decreased risk of upper respiratory infections.

So stay active, but not too active, if you want to keep a cold a bay. If you’re a marathoner…we wish you good luck and would love to talk with you about ways to stay healthy too!