It's a familiar scenario: You wake up one morning feeling like a piece of lead, with a sore throat and clogged sinuses. Only two weeks until your half marathon, you do what many runners would: Pop some vitamins, lace up and head out the door. Why should a runny nose compromise your hard-earned gains? What's the worst that could happen?
We paid a visit to a few doctors to find out exactly how running affects your immune system. Here are the experts' diagnoses on common beliefs about running and wellness.
Running Regularly Keeps You From Getting Sick
It's not your imagination: People who exercise regularly report fewer colds than their sedentary peers. "It's been well-established by several studies in the sports medicine world that athletes who engage in moderate activity (eg. 10 to 20 miles per week) have fewer viral infections," says 30-year running veteran Dr. Jean Kayser, an OB-GYN at Kaiser Permanente in Walnut Creek, California.
Dr. Michael Mohseni, a Jacksonville, Florida-based Mayo Clinic ER physician, explains how running boosts immunity: "Essentially there is immunoglobulin A (IgA) in the blood, which is expressed in the mucous in your nose and saliva. Studies show that with moderate exercise, you produce more of this substance."
IgA triggers cells to identify and fight foreign substances like bacteria and viruses--particularly those that come in contact with mucous membranes coating the nasal passages. Mohseni, who is currently heading up a study to examine how running affects the body by analyzing the health of marathoners who completed the 2008 26.2 with Donna, reminds us that every runner is different.
"The effect that running has on your immune system is very individual and dependent on your degree of fitness."
There is a flip side. David Nieman, director of the Appalachian State University Human Performance Laboratory, has spent more than 20 years doing research on how running and other forms of exercise affect the immune system; his extensive body of research still serves as the watermark for current studies on the topic.
He wrote in the 2001 President's Council on Physical Fitness and Sports report on exercise and immune function, "Many components of the immune system exhibit adverse change after prolonged, heavy exertion lasting longer than 90 minutes...During this 'open window' of impaired immunity, which may last between three and 72 hours depending on the immune measure, viruses and bacteria may gain a foothold."
Those who engage in intense training are more prone to frequent infections because of the physical stress on the body and the immune system, explains Kayser. "Stress hormones adversely affect the immune system by decreasing the ability to fight infection."
So, it's true that people are more susceptible to getting sick immediately following a marathon. But even with the risks of heavy training, running offers benefits that outweigh them. "Balancing physical and emotional life stress with running or other exercise will definitely boost your immune system," Kayser says.