Exercise and Immunity

Exercise Immunology is a relatively new area of research in the medical field. Though the majority of studies on the effects of exercise on immunity have happened after 1990, one of the first documented papers was published in 1902 by Larrabee – he studied the changes in white blood cells in Boston marathon runners.

Immunity is our body’s defense against infections. When our body detects pathogens (antigens), the immune system works to recognize the antigens and get rid of them. Many cells and organs work together to protect our bodies against infections. White blood cells (leukocytes) play an important role in the immune system. There are different types of white blood cells – phagocytes (e.g., neutrophils) destroy invading pathogens and lymphocytes help to remember the pathogens and destroy them. B lymphocytes make antibodies that lock onto specific antigens. They act like an intelligence system that detects invasion and catches the pathogen. T lymphocytes act like soldiers and destroy the pathogens detected by B lymphocytes. Hence the T lymphocytes are often called the killer cells. Helper T lymphocytes coordinate the overall immune response – stimulate B cells to produce more antibodies and killer T cells to destroy the invading pathogens.

Immunity can be categorized into three types:

1. Innate or natural immunity – we are born with it.

2. Acquired immunity – develops throughout our life as we get exposed to pathogens.

3. Passive immunity – antibodies are acquired from an external source.

The immune system is very responsive to exercise and exercise has a profound impact on the normal functioning of the immune system. The effects of exercise on the immune system are as follows:

1. Moderate-to-vigorous intensity exercise of about 60 minutes has a positive impact on the immune system. Each session of exercise improves the anti-pathogen activity of macrophages, neutrophils, and killer cells, and increases the circulation of immunoglobulins (antibodies) and anti-inflammatory cytokines. This enhances the defense activity of the immune system and our metabolic health.

2. Immunosurveillance improves with regular moderate exercise. When the body detects invasion by pathogens quickly, it can neutralize the pathogens before it causes any damage to the body.

3. Regular moderate exercise has an anti-inflammatory effect and this reduces inflammation in the body. Though moderate inflammation is required for the efficient functioning of the immune system, exaggerated inflammation can damage the body.

4. Obesity, metabolic syndrome, atherosclerosis, some cancers, and type 2 diabetes are characterized in part by high inflammation, oxidative stress, and immune dysfunction. Exercise helps to counter the disease process by stimulating cellular and molecular changes throughout body tissues that promote anti-inflammatory and antioxidant responses and augment immunosurveillance.

5. Stress hormones (e.g., cortisol) have a detrimental effect on the immune system. Regular moderate exercise helps to reduce the levels of stress hormones in the body and this helps in the proper functioning of the immune system.

6. Immunosenescence is defined as immune dysregulation with aging. Regular moderate exercise helps to regulate the immune system and delays the onset of immunosenescence.

Words of caution - prolonged excessive exercise can lead to increased inflammation, oxidative stress, transient immune dysfunction, and muscle damage. For people indulging in excessive prolonged exercise, it is extremely important to take adequate rest and proper anti-inflammatory, anti-oxidant, and tissue-building nutritional support. Otherwise, excessive exercise can be detrimental to immunity.