The COVID-19 pandemic has sparked widespread interest in improving immune function. In addition to practicing social distancing and good hygiene, many people are searching for ways to build a stronger immune system.

Exercise plays a vital role in maintaining a healthy immune system.^[1] Since many gyms and parks have been temporarily closed in an effort to slow the spread of the virus, it can be challenging to find ways to get enough exercise.

Thankfully, one of the best researched forms of exercise doesn’t require a gym membership or additional equipment. That form of exercise is walking.

Active Individuals Have Fewer Upper Respiratory Symptoms

Researchers have found that people who exercise regularly are less likely to experience upper respiratory symptoms such as coughing, sore throat, or runny nose. Adults who engaged in aerobic exercise at least five days per week had 43% fewer days with upper respiratory symptoms over a 12-week period than those who exercised no more than once per week.^[2] Another study found that adults who exercised at least three days per week were 26% less likely to have the common cold during a yearlong period.^[3]

These immune system benefits aren’t exclusive to people engaged in formal exercise. Two studies have found an approximately 20% lower risk of upper respiratory symptoms in people who are the most physically active.^[4][5] Another study found similar results in a group of older adults at an average age of 70.^[6]

Walking Programs Lead to Fewer Upper Respiratory Symptoms

When researchers decided to test the cause-and-effect relationship between exercise and immune function, they selected brisk walking as the exercise of choice. Brisk walking is generally defined as walking at a pace of 2.5 to 4.0 miles per hour.^[7]

Most studies have found that a program of brisk walking for 30-45 minutes per day, 5 days per week, leads to fewer respiratory symptoms.^{[8][9][10][11]} These programs have ranged from 8 weeks to 15 weeks in duration and have included a variety of age groups, including those 65 and older.

A Single Exercise Session Can Positively Impact the Immune System

We’ve learned that walking programs lasting at least 8 weeks can lead to fewer upper respiratory symptoms, but an important question remains: Can we strengthen our immune system in less than 8 weeks?

It appears that the answer is “yes.”

A single session of brisk walking or moderate-intensity cycling for 20-30 minutes leads to increased activation of several different types of immune cells (Nieman 2005, Campbell 2009, Bigley 2014).^[12][13][14] With regular exercise, these positive responses are thought to contribute to a stronger immune system.1

Next Steps (Literally)

Start a walking program today by using the following research-based guidelines:

• Walk for 30-45 minutes per day.
• Walk at a pace of 2.5 to 4.0 miles per hour, which equates to walking one mile in 15 to 24 minutes.
• Aim to perform this walking routine five times per week.

References

1. Nieman, D. C., & Wentz, L. M. (2019). The Compelling Link between Physical Activity and the Body’s Defense System. Journal of Sport and Health Science, 8(3), 201–217. doi: 10.1016/j.jshs.2018.09.009
2. Nieman, D. C., Henson, D. A., Austin, M. D., & Sha, W. (2010). Upper Respiratory Tract Infection Is Reduced in Physically Fit and Active Adults. British Journal of Sports Medicine, 45(12), 987–992. doi: 10.1136/bjsm.2010.077875
3. Zhou, G., Liu, H., He, M., Yue, M., Gong, P., Wu, F., … Zhang, X. (2018). Smoking, Leisure-Time Exercise, and Frequency of Self-Reported Common Cold among the General Population in Northeastern China: A Cross-sectional Study. BMC Public Health, 18(1). doi: 10.1186/s12889-018-5203-5
4. Matthews, C. E., Ockene, I. S., Freedson, P. S., Rosal, M. C., Merriam, P. A., & Hebert, J. R. (2002). Moderate to Vigorous Physical Activity and Risk of Upper-Respiratory Tract Infection. Medicine & Science in Sports & Exercise, 34(8), 1242–1248. doi: 10.1097/00005768-200208000-00003
5. Fondell, E., Lagerros, Y. T., Sundberg, C. J., Lekander, M., Bälter, O., Rothman, K. J., & Bälter, K. (2011). Physical Activity, Stress, and Self-Reported Upper Respiratory Tract Infection. Medicine & Science in Sports & Exercise, 43(2), 272–279. doi: 10.1249/mss.0b013e3181edf108
6. Kostka, T., & Prączko, K. (2007). Interrelationship between Physical Activity, Symptomatology of Upper Respiratory Tract Infections, and Depression in Elderly People. Gerontology, 53(4), 187–193. doi: 10.1159/000100017
7. U.S. Department of Health and Human Services. Physical Activity Guidelines for Americans, 2nd edition. Washington, DC: U.S. Department of Health and Human Services; 2018.
8. Nieman, D., Nehlsen-Cannarella, S., Markoff, P., Balk-Lamberton, A., Yang, H., Chritton, D., … Arabatzis, K. (1990). The Effects of Moderate Exercise Training on Natural Killer Cells and Acute Upper Respiratory Tract Infections. International Journal of Sports Medicine, 11(06), 467–473. doi: 10.1055/s-2007-1024839
9. Nieman, D. C., Henson, D. A., Gusewitch, G., Warren, B. J., Dotson, R. C., Butterworth, D. E., & Nehlsen-Cannarella, S. L. (1993). Physical Activity and Immune Function in Elderly Women. Medicine & Science in Sports & Exercise, 25(7), 823–831. doi: 10.1249/00005768-199307000-00011
10. Nieman, D. C., Nehlsen-Cannarella, S. L., Henson, D. A., Koch, A. J., Butterworth, D. E., Fagoaga, O. R., & Utter, A. (1998). Immune Response to Exercise Training and/or Energy Restriction in Obese Women. Medicine & Science in Sports & Exercise, 30(5), 679–686. doi: 10.1097/00005768-199805000-00006
11. Çiloğlu, Figen. (2005). The Effect of Exercise on Salivary IgA Levels and the Incidence of Upper Respiratory Tract Infections in Postmenopausal Women. Kulak burun boğaz ihtisas dergisi : KBB = Journal of ear, nose, and throat. 15. 112-6.
12. Nieman, D. C., Henson, D. A., Austin, M. D., & Brown, V. A. (2005). Immune Response to a 30-Minute Walk. Medicine & Science in Sports & Exercise, 37(1), 57–62. doi: 10.1249/01.mss.0000149808.38194.21
13. Campbell, J. P., Riddell, N. E., Burns, V. E., Turner, M., Zanten, J. J. V. V., Drayson, M. T., & Bosch, J. A. (2009). Acute Exercise Mobilises CD8 T Lymphocytes Exhibiting an Effector-Memory Phenotype. Brain, Behavior, and Immunity, 23(6), 767–775. doi: 10.1016/j.bbi.2009.02.011
14. Bigley, A. B., Rezvani, K., Chew, C., Sekine, T., Pistillo, M., Crucian, B., … Simpson, R. J. (2014). Acute Exercise Preferentially Redeploys NK-cells with a Highly-Differentiated Phenotype and Augments Cytotoxicity against Lymphoma and Multiple Myeloma Target Cells. Brain, Behavior, and Immunity, 39, 160–171. doi: 10.1016/j.bbi.2013.10.030