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Can Exercise Weaken the Immune System?

November 30, 2020

By Sadie Engelken, Duke Diet & Fitness Intern from Carroll University with the supervision of the Duke Diet Fitness Team.

The immune system is the body’s protection system. The body recognizes and defends against bacteria, viruses, and foreign and/or harmful substances to prevent or limit infection or disease. Regular exercise is an effective way to keep the immune system strong; however, there is a lot of conflicting information about how to keep your immune system in shape. In this week’s blog post, we outline five key points to think about when strengthening the immune system through regular exercise.

Interval training can be an effective way to strengthen the immune system.

Research about the effects of regular exercise on the immune system is still ongoing.

Previous research stated that acute bouts of vigorous and/or prolonged exercise resulted in detrimental effects on the immune system, including an increased risk of infection and decreased blood immune cells an increased likelihood of becoming sick the following days.3 The opposite has now been supported. Current research shows that after an acute bout of aerobic activity there is a redistribution of immunity cell components resulting in improved surveillance, coordination, and regulation of the immune system. These results, therefore, support that high-intensity exercise; especially in the form of interval training can be an effective way to strengthen the immune system. 2, 6

Physical exercise can strengthen your immune system.

Increased circulation results in more mobilization of immune cells, removal of damaged cells, decreased inflammation and enhanced bodily functions. The most beneficial impact occurs when exercise comprises a lasting, maintained routine of both aerobic and resistance training. The impact of these benefits increases over time and each mode of training improves the immune system in different ways. Aerobic training works on the immune cells themselves by increasing their numbers and activity. Resistance training improves inflammatory status and removal of diseased or mutated tissues. Research has shown these benefits can be seen in as little time as one month and even if training were to be discontinued, the benefits would remain even after two months. 1, 2, 4, 6

When can exercise weaken the immune system?

It is important to note there is a point at which exercise can weaken the immune system. With long-term intensive or excessive training, multiple parts of the system can weaken resulting in decreased function and increased risk of infection. This occurs when the duration of a single exercise session is too long, the intensity is too high during, or when a person does not allow the body time to recover.1, 2, 5

Key takeaways

  • Brief bouts of vigorous activity will improve the immune system.
  • A routine of both aerobic and resistance activity will give the best boost to your immunity.
  • Overtraining can result from long-term, intensive, excessive training resulting in declined function and increased risk of infection.
  • It is important to check in with your emotions, performance, and body to make sure you are not overtraining.
  • Most importantly, keep moving because any activity will provide immediate benefits to the immune system.


1. Au, K. (2017, November 6). Should you exercise when sick?

2. Calabrese, L. (2017, July 28). How to Train and Maintain Your Immune System.

3. Campbell, John P., and James E. Turner. Debunking the Myth of Exercise-Induced Immune Suppression: Redefining the Impact of Exercise on Immunological Health Across the Lifespan.

4. Harvard Health Publishing. (2018, July 16). How to boost your immune system.

5. MacKinnon, L. T. (2000), Overtraining effects on immunity and performance in athletes.

6. Sellami, Maha & Gasmi, Maha & Denham, Joshua & Hayes, Lawrence & Stratton, Dan & Padulo, Johnny & Bragazzi, Nicola. (2018). Effects of acute and chronic exercise on immunological parameters in older adults.

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