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Your Immune System & Exercise

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What is exercise immunology?

I’d never heard of exercise immunology, but its principle makes sense:  exercise boosts the immune system and reduces inflammation.  With exercise, the old adage goes “no pain, no gain”; but if we are constantly tearing our bodies and muscle tissue down, isn’t that likely to lead to being worn out and leave us susceptible to catching more bugs?  It’s a question that was posed in recent weeks by the University of Bath.

Researchers opened up a debate in the scientific community about the benefits of exercise immunology, how exercise can boost immunity, and why it’s so important to stay active to the extent possible even under these restricted times.

Even though the principle of exercise immunology seems logical, it still leaves a lot of questions about the increases in inflammation and biological responses that heavy exercise brings–but the statistics are where the physiology of exercise immunology shines.

Moderate, “near-daily” exercise (such as walking or jogging) for a period of just twelve to fifteen weeks can reduce the number of symptoms associated with upper respiratory tract infections (colds, flus, and other viruses) by 25-50% over people who are don’t exercise and are sedentary.  It’s not extreme exercise that is achieving these benefits.

Exercise has some interesting effects regarding upper respiratory tract infections (URTIs).  If you’re exercising regularly, you’ll have better immune function and lower your risk of catching a cold, flu, or other virus.  And surprisingly, if you’re exerting yourself for more sustained and heavier exercise, it will have the opposite effect.

The answers may lie in what’s happening within the body when you’re exercising.  If you’re pushing yourself during workouts, your stress hormones increase.  These stress hormones can lower your immunity.  During heavy periods of exercise, the metabolic activity is increased to such a point that pro-inflammatory cytokines are elevated.  During moderate exercise, however, these stress hormones are not elevated.

 A study involving 547 adults who exercised regularly showed a reduction of 23% in the likelihood of contracting an upper respiratory tract infection (URTI), compared to those who exercised harder but more irregularly.

Women, who were not in top physical shape, demonstrated that exercising moderately (about 4 days a week for a total of 166 minutes) reduced the risk of getting a cold by three times, compared to those who did not exercise.  Women who walked frequently or jogged more than 2 hours weekly had an 18% reduction in the risk of pneumonia, and elderly women who walked 5 days per week reduced their incidence of URTI to only 21%.  The elderly women who exercised with traditional calisthenics also reduced their risk of URTI, but they still accrued a 50% chance of contracting an URTI—which was a higher risk than those who walked for exercise.

For men between the ages of 33 and 90, the days that they suffered the symptoms of URTI decreased with more physical activity, giving them 64% less days they were sick.

The data shows clear benefits in maintaining moderate, daily exercise.  Fitness can be touted as all or nothing, hence the “weekend warriors” who are sedentary most of the workweek and then push themselves extremely hard on the weekend at various fitness classes and regimens.  It’s important to remember that, as with most things, moderation is the key.

Exercise immunology has been studied for the past 40 years.  It studies how different types of exercise affects the immune system and delves into the immune surveillance theory (which states that the immune system is always on the lookout for harmful cells).  Exercise immunology is fascinating, and it can get technical—but it has real benefits that can be applied to the real world.

Exercising moderately for 45 minutes before a flu shot can improve your body’s antibody response.  It’s worth the time to try to walk as close to every day as possible!


Simpson, RJ, et al. “Can Exercise Affect Immune Function to Increase Susceptibility to Infection?” Exerc Immunol Rev., vol. 26, 2020, pp. 8–22., https://www.ncbi.nlm.nih.gov/pubmed/32139352.

Nieman, David C. “Clinical Implications of Exercise Immunology.” Journal of Sport and Health Medicine, vol. 1, no. 1, May 2012, pp. 12–17., doi:https://doi.org/10.1016/j.jshs.2012.04.004.


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