How too much movement can lower our immune system, and just the right amount can help us kick illness to the curb.

Have you ever had a year where getting ready for the holidays felt like running a marathon? And then, as soon as your holiday started, you got sick? The funny thing is, this happens to actual runners all the time. Studies show they are most likely to get sick after running a marathon.

Training, just like the lead up to a big holiday, is a stress on our bodies. This stress can create positive changes, like better endurance, or it can affect us negatively, with overuse injuries or chronic stress. The key is to get enough stress without going overboard.

The standard recommendations for physical activity are 150 minutes per week at a moderate intensity, or 75 minutes per week of vigorous intensity. In this article, we’ll look at how this level of physical activity can help prevent illness, and how it can help when we do get sick.

Preventing disease vs. illness

There are no guarantees when it comes to preventing sickness. Nothing gives us 100 percent immunity. But what we can do is reduce our risk of disease, and movement is one of our best tools for doing just that.

According to “Exercise is Medicine,” compared to being sedentary, meeting the standard physical activity guidelines can help us reduce our risk of:

  • Recurrent breast cancer (by 50 percent)
  • Colon cancer (by more than 60 percent)
  • Alzheimer’s (by 40 percent)
  • Heart disease and high blood pressure (by 40 percent)
  • Stroke (by 27 percent)
  • Type II diabetes (by 58 percent)
  • Depression (by 45 percent)

It can also lower our risk of upper respiratory infection by 43 percent and maintain our bone mineral density, which can prevent osteoporosis.

But you can have too much of a good thing. Too much physical activity causes a temporary reduction in our immune function. Experts think it may be due to a rise in stress hormone levels that occurs when we work out either for long periods of time, or when we’re already under a lot of stress.

This is what’s happening when a marathoner gets the flu the week after a race—or when we find ourselves knocked out with a cold on our first day of vacation.

A 2014 study out of Bangor University found that the length of a workout, rather than its intensity, triggered this effect. Thirty minutes of moderate or vigorous physical activity had no effect, but 120 minutes of moderately paced running caused a reduction in immune response.

The takeaway is that moderate physical activity will help boost your immune system to resist infection and lower your risk of major noncommunicable diseases, as long as you don’t push the length of your workout. And that’s nothing to sneeze at.

All that said, if you’re sick enough to visit your doctor, make sure you ask their advice before starting any fitness program. Everyone responds differently to physical activity, and your doctor will have the best understanding of all the considerations that are important for you.

Things you wish you knew yesterday

If you’re already sick, learning to reduce risk and prevent infection won’t cut it. (It’s like this scene in “The Wedding Singer.”)

You need things you can use to feel better ASAP. What’s amazing is that the standard fitness guidelines that help prevent illness also help us feel better.

Our lymphatic system is responsible for making and transporting our immune cells and removing waste from our system. Lymph fluid moves around the body mostly via the pumping actions of our muscles. So in order for lymph fluid to move, we need to move. Exercises that require movement from the ground to a standing position are one of the best ways to get a lot of muscles going without being too strenuous.

And strenuous is not the answer when you’re sick. A 2005 study from the University of Illinois that found mice infected with the flu had an 82 percent survival rate when they worked out moderately, but only a 30 percent survival rate when the workout was “extreme.”

Moderate physical activity really is key. A 1998 study found that moderate activity made cold sufferers feel better than simply resting, even though their non-exercising counterparts experienced the same symptoms and length of illness.

When you’ve got an acute infection—like a cold or the flu—doctors recommend what they call the “neck check” before working out. If your symptoms are only above the neck, like a runny nose or a headache, feel free to train. But if your symptoms are below the neck or all over, like a fever or an upset stomach, it’s better to rest until you feel better.

Longer-term solutions

Noncommunicable diseases are chronic conditions that require more careful management and planning. But movement is often a large part of the treatment plan.

Take breast cancer, for instance. According to the National Cancer Institute’s information on physical activity, “women who exercised moderately … after a breast cancer diagnosis had approximately 40 to 50 percent lower risks of breast cancer recurrence, death from breast cancer and death from any cause compared with more sedentary women.”

Programs like UW Well-Fit at the University of Waterloo offer customized movement plans specifically for cancer patients. One testimonial on the program’s website reveals the following:

“Unbelievably to me, the recommendation of the Well-Fit team was that I start the … program during the time I was receiving chemotherapy. I dragged myself there twice a week, so tired, sore and sometimes nauseated.

“Caryl and Lori expertly and patiently led us through the cardiovascular and strength training exercises. Each day the tiredness, the soreness and nausea disappeared for a while. Each day I felt stronger. I began to look forward to the class: to exercising, celebrating our success and supporting each other when bad things happened.”

Physical training is stress, so we need to get the amount right, especially when we’re sick. But when we follow the guidelines, we unlock the power to prevent illness, to feel better and to increase our chances of survival if we do get sick.

Photo credit: cyano66, Thinkstock