Exercise and Viruses Exercise Immunology

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This article was edited and updated on December 12, 2021.

Two Questions: Can I exercise when I have a cold? If I exercise will I prevent a cold?

This article could be about whether or not you should exercise when you have a virus.

Could. That's the important word in that sentence.

Because that is not what this article is about.

This article is about whether or not the exercise you have done in the past will help you fight viruses on any particular day — today, tomorrow, or in the future.

In other words, does exercise strengthen your immune system? Will exercise help you to do battle with a virus? 2

Exercise Immunology

Exercise immunology has become almost big business. There are organizations which support research on this topic — The International Society for Exercise Immunology, to name but one (see sidebar for the organization's goals).

There is a fairly strong body of evidence that exercise will indeed help your immune system.

Dr. David C. Nieman, Ph.D., from Appalachian State University, published in 2003 the results of his research in a document titled "Current Perspective on Exercise Immunology." 3 His introduction states:

"By far, the most important finding that has emerged from exercise immunology studies is that positive immune changes take place during each bout of moderate physical activity. Over time, this translates to fewer days of sickness with the common cold and other upper respiratory tract infections. This is consistent with public health guidelines urging individuals to engage in near-daily physical activity of 30 minutes or more." [My emphasis.]

It should be noted, however, that Dr. Nieman says there is a tipping point where activity is less helpful, especially when other factors are involved:

"Risk of upper respiratory tract infections can increase when athletes push beyond normal limits. The infection risk is amplified when other factors related to immune function are present, including exposure to novel pathogens during travel, lack of sleep, severe mental stress, malnutrition, or weight loss. Many components of the immune system exhibit adverse change after prolonged, heavy exertion lasting longer than 90 minutes. These immune changes occur in several compartments of the immune system and body (eg, the skin, upper respiratory tract mucosal tissue, lung, blood, and muscle). During this "open window" of impaired immunity (between 3 and 72 hours, depending on the immune measure), viruses and bacteria may gain a foothold, increasing the risk of subclinical and clinical infection." [My emphasis]

His final conclusion is:

"In general, if symptoms are from the neck up, moderate exercise is probably acceptable (and some researchers would argue even beneficial) when an athlete is sick, whereas bed rest and a gradual progression to normal training are recommended when the illness is systemic."

So, in the end, this article does include one small bit of advice about whether you should exercise while you have a virus.

But here's the more important message to get from what has been said so far: Since heavy exertion may weaken the immune system, it is important to concentrate on moderate activity on a daily basis.

Moderate Activity

What does "moderate activity" mean? It is different for every person, depending on your age, gender, and general health.

In most studies, walking 35-45 minutes a day, compared to those who do no physical activity, fare better and have "about 505 fewer days with cold symptoms" than those who don't exercise at all.

Studies vary, of course, as to what it means to exercise moderately. In the fitness industry, moderate exercise is achieving a heart rate that is within 50 to 60 percent of your resting heart rate. (See below for how to calculate this.) But what "moderate activity" is will be different for each individual.

Here are some suggested activities for a normal adult with no health issues:

Other daily activities such as these also qualify as moderate activity:

To be absolutely certain that you are reaching the right heart rate level, you can learn to count your heartbeats.

Here is how it's done: Subtract your age from 220. That is your maximum heart rate. Then calculate 50% and 85% of that number because you do not want to exercise at your maximum heart rate. You will end up with two numbers which is a target range for your heart rate to be while exercising.

Example: A 70-year-old woman would subtract 70 from 220 to get a Maximum Heart Rate of 150 (220-70=150). However, she does not want to exercise with her heart beating at 150 beats per minute. Instead, she should exercise at 50-85% of her Maximum Heart Rate which would be between 75 and 128 (150 X .50 = 75 and 150 X .85 = 128). Every time she checks her heart rate while exercising, it should be between those two numbers.

Why does moderate activity help the immune system?

Research has shown that "during moderate exercise, several positive changes occur in the immune system." Moderate activity does not release or elevate stress hormones or pro-and anti-inflammatory cytokines. Stress hormones, if activated, can suppress immunity. Cytokines are indicative of intense metabolic activity.

Although the immune system returns to pre-exercise levels very quckly after exercise, each session represents a boost in immune surveillance that appears to reduce the risk of infection over the long term.


One can conclude from the research that moderate activity is good for humans in almost any situation and it can actually enhance the immune system, making you less likely to have trouble fighting off a virus.

Oscar Wilde said, "Everything in moderation, including moderation." It applies in exercise as well as in every other aspect of our lives. High-intensity exercise may be worthwhile at times, but moderation in our daily activities is worth considering.

This article is part of a series about various health conditions and the benefits of exercise. The other articles are:

I am a BCRPA-certified fitness instructor in Vancouver, BC. I teach four classes at the West End Community Centre in Vancouver, BC, mostly designed for the older adult. The Inevitable Disclaimer: Everything published here expresses only my opinion, based on my training and research. What you do with the information is entirely your own responsibility. I am not liable for any injury you suffer that seems to be related to anything you read here. Always consult your doctor before beginning an exercise program. For other articles, return to the table of contents.

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  1. These three dots behave exactly like a footnote. Click on them and you will get more information about the topic. ↩︎

  2. If you were hoping to learn about whether or not you should exercise when you have a cold or the flu, this article won't answer that question, though you will find plenty of opinions about that on the internet. ↩︎

  3. His research was published in Science Direct. You can find the link [here] (http://www.sciencedirect.com/science/article/pii/S2095254612000075). ↩︎