How Exercise Affects Your Immunity

March 4, 2017 Updated: March 4, 2017
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Most competitive athletes follow a stress and recover training program, and so should you, even if you don’t compete in sports.

To make muscles stronger, you need to exercise intensely enough to damage them. To increase your ability to take in and use oxygen, you need to exercise hard enough to become short of breath.

However, several recent studies show that if you don’t follow your hard workouts with easy ones, you may be suppressing your immune system, leading to increased risk of developing diseases, from colds to autoimmune disease.

Healing muscles after exercise is governed by your immune system.

A 2016 study published in the Journal of Strength and Conditioning Research showed that doing intense workouts actually reduces the immunity of elite soccer players. Intense exercise lowered salivary levels of immunoglobulin A (IgA), an antibody in secretions (including saliva, tears, and stomach fluids) that prevents germs from entering the tissues and bloodstream. The same reduction in salivary IgA occurred in football players after games, according to a 2015 study published in the Journal of Sports Sciences. 

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This effect has also been shown in non-athlete exercisers when they perform intense workouts on consecutive days without allowing time for recovery, according to a 2016 study published in Frontiers in Physiology.

The researchers also found that consecutive intense workouts reduce levels of anti-inflammatory cytokines, a type of protein produced by the white blood cells. Cytokines control the strength of your immune system’s response to invading germs. Having low levels of cytokines increases the chances of your immune system attacking your own body in the same way that it tries to kill germs, which can lead to various autoimmune diseases, such as chronic fatigue syndrome or inflammatory bowel disease. Other studies show that consecutive days of intense exercise may also reduce your white blood cell count.

All of this is caused by doing too many consecutive intense or long-duration workouts, including not taking enough rests and not stopping when your muscles burn or you feel excessively tired.

How Muscles Heal After Intense Exercise

Yoga instructor Tracye Warfield, right, participates in a yoga class in Times Square during the 13th annual Solstice in Times Square, Sunday, June 21, 2015, in New York. Warfield was one of several thousand who practiced yoga during six different classes held throughout the day to mark the summer solstice. (AP Photo/Julie Jacobson)
Yoga instructor Tracye Warfield, right, participates in a yoga class in Times Square during the 13th annual Solstice in Times Square, Sunday, June 21, 2015, in New York. Warfield was one of several thousand who practiced yoga during six different classes held throughout the day to mark the summer solstice. (AP Photo/Julie Jacobson)

Muscles are made up of hundreds of thousands of individual fibers. To make muscles stronger, you have to damage them. Then when they heal, they become larger.

You can tell that you are damaging a muscle during exercise by the burning you feel in the muscles and the soreness you feel the next day. If you do an easy workout when your muscles feel sore, those muscles will become stronger. If you do an intense workout on sore muscles, you may tear and injure them.

Healing muscles after exercise is governed by your immune system. The same cells and cytokines that kill germs initiate this healing process. When you feel sore after intense exercise, your immune system goes into high gear to heal the damaged muscle tissue.

If your immune system stays active in the same way for prolonged periods, it can begin to attack your healthy tissues.

If you do another intense workout when you feel sore and are trying to heal, your body senses that you are causing further damage, so it reduces the amount of white blood cells and proteins that initiate muscle healing.

Your body does this because if your immune system stays active in the same way for prolonged periods, it can begin to attack your healthy tissues in the same way that it attacks germs. This is called inflammation, and it can lead to heart attacks, as overactive immunity can cause holes to form in arteries and lead to the formation of plaques. Cancer can be caused by your immunity attacking your own cells and damaging the genetic material that controls cell growth.

When you are exercising properly—taking hard workouts to strengthen your muscles followed by easy workouts that allow your muscles to heal—you are also strengthening your immunity by allowing it to “turn up” and “turn down.” 

Listen to Your Body

• Try to alternate harder workouts with easy recovery ones on consecutive days.
• If you are training properly, expect to feel sore every morning when you wake up. If your muscles feel better after a 5- to 10-minute warmup, do your planned workout.
• If you don’t feel better during your warmup, go home, because continuing to exercise will only increase your chances of injuring yourself. 

Gabe Mirkin, M.D., has been a practicing physician for over 50 years. He is board-certified in sports medicine, allergy and immunology, pediatrics, and pediatric immunology. This article was originally published on DrMirkin.com. Subscribe to his free weekly Fitness & Health newsletter.