Once when I was young and foolish, my roommates and I suddenly decided we would all get in shape. We got up the next morning at 5:00 AM and ran about 3 miles. All of us spent the rest of the week in bed with a bad cold. Thus the golden rule of health applies to exercise as well as other things: Don’t be stupid.

As the above story points out, exercise is not good for your immune system if you overdo it. But it is well documented that sensible exercise is good for your immune system. For starters, exercise helps to promote the flow of lymph. Lymph is the fluid that is released from your blood into the tissues that eventually finds its way back into the bloodstream. Together, the blood and the lymph constitute the two major highways for transport of many of the cells (leukocytes) and molecules (such as antibody) of your immune system. The reason that exercise is important for the flow of your lymph is because, unlike blood, this fluid is not pumped by the heart. Instead, its flow is dependent upon gravity and body movement.

As pointed out in other articles on this site, immunity includes innate immunity and acquired immunity. Your respiratory system (bronchioles, lungs etc.) is one of the major routes by which infectious agents enter your body since you take in a large volume of air everyday. In terms of preventing colds, flu and other respiratory tract infections, innate immunity in these areas includes what is called the ciiary escalator. This “escalator” involves the movement of mucous containing foreign particles that you have breathed in, upwards (that’s the escalator part) by a whip-like action of thousands of tiny hair-like fibers (called cilia). This is your body’s way of getting bad stuff like viruses that you have breathed in up where you can cough and sneeze them out.

One way in which overdoing exercise can have a bad effect on immunity is through interfering with the ciliary escalator. This happens to ultra-marathoners who breathe in a lot of dry air through their mouths, which cools and dries the mucous and slows down the movement of the cilia. This results in an impaired ability to get viruses and other particles out of the respiratory tract. Extreme exercise programs have also been shown to reduce antibody (acquired immunity) levels in the respiratory tract. . Furthermore, among those that really overdo it, the focus of the body’s energies on repair of excessively sore muscles, as well as chronic psychological stress (see the article: “Chill or be chilled” elsewhere on this web site) may also impair immunity. Fortunately, these effects are transient and may only present a problem in those who chronically overdo it, such as those involved in heavy military training, ultra-marathoners, and other elite athletes. By the way, extra vitamin C is often taken by people in this group to aid in tissue repair and may also have a direct beneficial effect on immunity (see “Nutrition and Immunity” on this web site).

If you are like me, you have never been an ultra-marathoner and are in no danger of becoming one. For the rest of us, exercise is usually a good thing if we also exercise our brains and don’t try to jump into an exercise program without easing into it first. The other thing to avoid is continuing an exercise program in spite of being sick. A good rule of thumb I learned from our Wellness Center here at OSU is that if cold symptoms are all above the neck, it is probably okay to continue your exercise program. However, if you have symptoms below the neck (such as chills, aches, fever, a strange obsession for the Home Shopping Network (just kidding) etc), then rest is what you need. (My own rule of thumb is that if I feel as bad as I usually feel after working out before I have worked out, then skip it baby!)

Here’s the good news. Studies with human volunteers have shown that over the long term, moderate exercise (such as 45 minutes of exercise 5 times/week) reduces the incidence and severity of colds and flu, especially in older individuals who might otherwise be sedentary. So if you want to turn your leukocytes into little Arnold Schwartzneggers, then exercise sensibly, regularly, and moderately and you will be pumping up your immune system. If you want to read more about exercise and immunity, I recommend the following web site: www.physsportsmed.com.

This entry was posted on Friday, June 17th, 2005 at 11:13 am and is filed under Caring for the Immune System. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.