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  • Alaina Pupulin

Physical Activity and the Immune System

Edited by: Temi Toba-Oluboka

Immune System Overview:

  • The immune system is a large network of organs, cells and proteins that work together to protect you from foreign invaders (bacteria, viruses, parasites, and fungi) that cause infection, illness and disease.

  • Certain lifestyle changes can boost your immune system and help you avoid illness including smoking cessation, weight loss, healthy eating, exercising regularly, and maintaining proper hygiene.

  • Regular exercise can result in better sleep, improved moods, lower stress levels, and increased circulation of immune cells in your body — all factors that contribute to a healthy immune system.

Does exercise boost the immune system? Exercise stimulates cellular immunity Performing aerobic exercise at a moderate to vigorous intensity for an average of 30–45 minutes a day can stimulate cellular immunity by increasing the recruitment and circulation of the immune system’s defensive cells. This helps your body better prepare for a future infection by detecting it earlier.

Exercise raises body temperature

The brief rise in body temperature during and right after exercise may prevent bacteria from growing. This temperature rise may help the body fight infection better and is similar to what happens when you have a fever.

Exercise helps you sleep better

Regular physical activity can contribute to better overall sleep quantity and quality. Some research points to a higher risk of infection due to a reduction in antibodies and the production of inflammatory cytokines in people with a modest amount of sleep loss.

Exercise decreases risk of heart disease, diabetes, and other diseases

Exercise can reduce cardiovascular risk factors, prevent or delay development of type 2 diabetes, increase HDL (good) cholesterol, and lower resting heart rate. Having one or more of these conditions may make it more difficult for your immune system to ward off infections and viral illnesses.

Exercise decreases stress and other conditions such as depression

Moderate-intensity exercise can slow down the release of stress hormones while positively influencing the neurotransmitters in the brain that affect mood and behavior. According to some research, ongoing stress and depression can lead to a low chronic inflammation status that favors infections, diseases, and other illnesses.

Should you exercise when you’re sick?

  • Exercising while sick may make you feel worse or delay recovery, especially if you’re running a fever or experiencing severe symptoms.

  • If you’re experiencing above-the-neck symptoms like congestion, sneezing, sore throat, and runny nose, you may have the common cold and be okay to do some mild to moderate exercise which may help flush bacteria out of the lungs and airways.

  • If you have a fever or chills, body aches, a cough, or nausea, you could be dealing with a more serious condition, such as influenza or COVID-19, and should refrain from exercising.


Nieman D.C., Wentz, L.M. (2019) The compelling link between physical activity and the body's defense system. J Sport Health Sci. doi: 10.1016/j.jshs.2018.09.009. Epub 2018 Nov 16. PMID: 31193280; PMCID: PMC6523821.

Simpson, R. J. (2020). Exercise, Immunity and the COVID-19 Pandemic. American College of Sports Medicine.

Kenny, G.P., McGinn, R. (2017). Restoration of thermoregulation after exercise. Journal of Applied Physiology.

Zee, P.C., Turek, F.W. (2006). Sleep and health: everywhere and in both directions. Arch Intern Med 166:1686-1688.

Irwin, M.R., Wang, M., Campomayor, C.O., Collado-Hidalgo, A., Cole, S. (2006). Sleep deprivation and activation of morning levels of cellular and genomic markers of inflammation. Arch Intern Med 166(16):1756-1762.

A. Caplin, F.S. Chen, M.R. Beauchamp, E. Puterman. (2021). The effects of exercise intensity on the cortisol response to a subsequent acute psychosocial stressor. Psychoneuroendocrinology.

Volume 131, 105336, ISSN 0306-4530.

Cañas-González B., Fernández-Nistal A., Ramírez J.M., Martínez-Fernández V. (2020). Influence of Stress and Depression on the Immune System in Patients Evaluated in an Anti-aging Unit. Front Psychol. 4;11:1844. doi: 10.3389/fpsyg.2020.01844. PMID: 32849086; PMCID: PMC7417678.

Martin, S. et al. (2009). Exercise and respiratory tract viral infection. Exerc Sport Sci Rev. 2009 October; 37(4): 157–164. Retrieved from:

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