A moderate exercise can boost up your immune system, whereas strenuous exercise may lead to decrease in host immune response. Extreme exercise can cause the transient decrease in white blood cell (Leukocyte) functions, i.e. it creates an “open window” for infection. During this window of infection, there is great extent of access of viruses and bacteria into the host’s body which cause disease subsequently. Other factors which favour the organisms’ supremacy are- Psychological stress, inadequate nutrition like deficiency of iron, zinc and vitamins- A, D, E, B6 and B12, lack of sleep, etc.
Prolonged exercise (>1.5 hour), without adequate supplementation of nutrients, has a pronounced impact on immune response. Strenuous exercise has a negative impact on innate immune response via phagocytosis, oxidative burst activity, neutrophil chemotaxis, toll like receptor expression and natural killer cell cytotoxicity activity. It has also great negative impact on the specific immune response via immunoglobulin production by B lymphocytes, antigen presentation by monocytes and macrophages, interferon-g production and proliferation of T lymphocytes. Mucosal Immune response is also compromised with extreme exercise. The cause for the depressed immune response in prolonged strenuous exercise is the production of stress hormones like epinephrine and cortisol, imbalance in the pro- and post- inflammatory cytokines like IL-6, IL-10, IL-1 receptor antagonist and soluble tumour necrosis factors (TNF).
Recently it has been found that the gene expression during extreme exercise is involved in down-regulation of immune response by producing anti-inflammatory cytokines. During exercise, IL-6 cytokine is released from the fatigued muscle which causes release of IL-10 and IL-1RA, adrenocorticotrophic hormone and cortisol, as well as acute phase reactants of hepatocytes (C reactive proteins).
Intense level of exercise may also affect the mucosal immune status. Heavy and chronic exercise may cause the low level of immunoglobulin in secretion, i.e IgA and IgM while moderate exercise may have positive effect on mucosal immune status. Low level of secretory immunoglobulin, particularly IgA1, is associated with respiratory diseases.
The immune system is not a single entity but a system. It involves many cell types orchestrating into a common goal to kick out the disease causing organisms. To function well it needs balance and harmony among all the cell types. Many studies have demonstrated that regular and moderate exercise is good for a healthy and long life. Regular and moderate exercise help in cardiovascular health, lower blood pressure, can control the body weight and protect against various diseases. Exercise directly promotes the circulation and thereby helps in circulating all the immune cells and other immune substances throughout the body so that they perform their functions efficiently. The role of exercise in boosting up of immune system is not fully uncovered though there is evidence of increase in circulating T lymphocytes in aerobic training like brisk walking.
The World Health Organisation recommendation for exercise is 300 minutes per week, i.e. 45 minutes aerobic exercise daily to boost up the immunological networks via good blood circulation throughout the body. Right amount of exercise reduces the chances of heart disease and keeps bones strong and healthy. Physical activity also helps in flushing out the microorganisms from respiratory and airways; the raised temperature right after exercise also helps in inhibiting the growth of bacteria. Normal exercise may include bicycling, playing different sports, walking, running, going gym, yoga, etc.
There are substantial evidences that moderate amount of exercise on daily basis helps in boosting of immune system and strenuous exercise may cause the aforesaid immune insult. About 24 hours of rest is required to restore the normal state of immune system after extreme exercise. Nutritional and other factors must be considered during chronic extreme exercises.
Ref: 1. Sports science Exchange journal (2015). Vol. 28 No.151, 1-6
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