Can you outrun cold and flu season?

Can exercise help you resist getting sick through cold and flu season?

Research supports the idea that regular exercise can be a great preventive measure to help you fight various bugs during cold and flu season. On the flip side of this idea, there seems to be a lot of confusing information and research on the affects of hard, vigorous exercise that may hinder your immune system.

Let’s look at one study done around mice and exposure to the flu virus. Studies done a few years ago on these mice found that sedentary mice exposed to the flu virus became sick at a fairly high rate. Mice that were placed into a moderate regular exercise also exposed to the flu virus had lower infection rates. However, mice that were placed into prolonged intense exercise had the highest rate of infection from exposure. This seems intuitively obvious — sedentary mice may have a weaker immune system than those mice who get moderate regular exercise — but too much exercise weakens their immune system? OK, we are talking about mice, and humans are different, so what is the answer? Does exercise help hold off colds and flu? If so, how much is the right amount of exercise?

The one consistent aspect of writing these columns is the fact that rarely do I find subject matter that does not have conflicting or contrary views or facts.

The simple answer to the question “Does exercise help fight off colds and flu?” is "yes." I don’t think anyone would argue against healthy, fit people usually having strong immune systems and recovering quickly in most cases, but to get a clear picture of this, we need to understand a couple of basics around our body’s immune defenses.

We have two parts to our immune system. The first is the innate immune system where our killer cells come from, the natural immunity we are born with. Then we have the adaptive immune system which learns to fight various pathogens we encounter as we go about our day-to-day lives. The two systems work together — the innate immune system calls the adaptive immune system into play when pathogens trigger an immune response. I will skip the rather long and detailed scientific explanation on how the two systems detect changes through cells and antigens to attack a pathogen.

When it comes to immune cells and exercise, not enough is known to truly understand what is going on with the pros and cons of exercise and illness. However, there are a few studies that have linked what are called T1 helper immune cells and exercise together. These T1 helper cells are the first line of defense against an invading pathogen. It seems that moderate exercise may play a boosting factor for these immune cells. As mentioned, little is known regarding the mechanisms at work between exercise and immune cells, but studies seem to support as much as a 10 percent reduction in flu with people who get moderate exercise each week.

Some researchers theorize that moderate physical activity strengthens the cardiorespiratory system which helps the body remove pathogens quickly from our body. Researchers have known for some time that exercise causes white blood cells to circulate faster, perhaps getting white blood cells to pathogens quicker than in someone with a sedentary lifestyle. The other aspects of exercise is it reduces our stress hormone cortisol and stress has certainly been lined to a lowered immune system. Exercise reduces stress which in turn may help protect you from getting sick.

One other positive outcome of regular exercise is an increase in your metabolism and while exercising, an increase in your body temperature. Both of these aspects may help the body fight infection more effectively.

We all know exercise is a good thing. Exercise also stresses the body and the body responds by building itself stronger and increases the body’s endurance. The process of breaking down and building up your body places your body under stress. The harder, more vigorous exercise, the tougher it is on your body, so it makes sense that intense workouts can weaken your body’s defense. I think it is fair to say that people who get regular moderate exercise are most likely boosting their immune system. I would also say that increasing your exercise intensity to boost your immune system may be a fool’s errand.

Like the mice I mentioned earlier from the study, if your lifestyle is sedentary, get into a routine of moderate exercise that includes cardio for a minimum of three hours a week. If you are already working out to a moderate exercise regimen, then you are probably giving your immune system that extra boost to keep you healthy through the cold and flu season. Extreme exercise can add too much stress to your body and research does indicate that you could be running your body’s defense down, making you more susceptible to colds and the flu.

One final note, if you already have a cold or flu, you should rest and recover. Working out with a bad cold or flu is not going to help you beat the bug. In fact, research has proven that your body needs downtime to recover, and going to the gym sick is only going to potentially spread the pathogens around to your fellow gym members.

Judd Jones is a director for the Hagadone Corporation.