Exercise and the immune system

what are the reasons for the higher risk of infection with long duration or higher intensity exercise?

-decreased blood levels of B cells, T cells, and natural killer cells -decreases in natural killer cell activity -decreases in nasal neutrophil phagocytosis -increase in pro- and anti- inflammatory cytokines collectively these results in a depression of the immune system's ability to defend against pathogens. It has been argued that there is an "open window: for pathogen invasion post intense exercise.

why does regular exercise give the immune benefits

1) B cell antibody production is elevated, natural killer cell count is elevated, monocyte count elevated, the more of these that are circulating, the more ready the immune system is 2) diet, sleep, mood is better with exercise

the mucosa in your respiratory, digestive, and genitourinary tract collectivly measure about

400 square meters and is another example of a physical barrier against bacteria and viruses

J curve

Dr. David Nieman created this curve to represent the risk of upper respiratory tract infection as a function of exercise intensity and/or amount

killer T cells Helper T cells Regulatory cells

Killer T cells- do the damage to the bacteria, recognize antibodies and kill foreign agent Helper T cells- secrete cytokines Regulatory T cells- recognize own cells (protection system) they protect the immune system from attacking itself and its own cells

when bacteria enter the body, macrophages recognize these invading cells and reach out to attach to the bacteria.

This results in the bacteria being engulfed into a pouch which is moved inside the macrophage and killed by powerful chemicals and enzymes within the macrophage

when stem cells divide the mature daughter cell makes

a choice to what type of blood it will become when it matures. These choices are not random and are highly regulated by complicated systems

a vaccine

allows B cells to recognize it so the immune system can respond rapidly

T cells

are a family of immune cells produced in bone marrow. T cells and B cells differ in several ways. First, B cells mature in the bone marrow, T cells mature in a specialized immune organ called the thymus (hence T cells). T cells do not produce antibodies but specialize in recognizing protein antigens in the body. T cells exist as Killer T cells, Helper T cells, and regulatory T cells

natural killer cells

are also produced in the bone marrow and are found in the blood liver, or spleen. They exit the blood and move into tissue to fight infection. They play two key roles, First, natural killer cells can destroy virus-infected cells, bacteria, parasites, and fungi. Second, natural killer cells also give off cytokines that help with immune defense

phagocytes

are cels that engulf bacteria in a process called phagocytosis. To remove unwanted bacteria, the body produces several different types of phagocytes which participate in the innate immune system. To key phagocytes are macrophages and neutrophils.

neutrophils

are leukocytes that also participate as phagocytes during a bacterial invasion similar to macrophages, neutrophils produce cytokines to alert other immune cells to the presence of the bacteria

blood cells, red and white, are made in

blood marrow- where they are produced from common self-renewing stem cells stem cells- one breaks in half- now 2- one can stay in place while the other can help

moderate aerobic exercise PROTECTS against infection

both epidemiological and randomized studies consistantly report that regular exercise results in 18-67% reduction in the risk of upper respiratory infection. This protection can be achieved with walking, jogging, cycling, swimming, etc. In general, 20-40 minutes of exercise at 40-60% VO2 max is adequate to provide protection.

cytokines

cellular components of the innate immune system, during the battle with bacteria, macrophages also produce proteins called cytokines. these are cell signals that regulate the immune system by facilitating communication between cells within the immune system. Some cytokines alert immune cells that the battle is ongoing and help recruit more immune cells. In this case, cytokines serve as a CHEMOATTRACTANT to attract more immune cells to the harmful bacteria. Other cytokines can promote fever and inflammation the stronger the infection the more macrophages and neutrophils are recruited to the area

exercise in cold conditions

few studies have examined immune response to exercise in cold, these studies have mostly involved short-duration exercise protocols lasting less than 1 hour and have compared immune responses following exercise in cold conditions with immune responses in hot rather than thermoneutral conditions. Nevertheless, although limited, the evidence to date does not support the popular belief that exercising in cold conditions suppresses the immune system.

B cells

function as antibody factories and can produce more than 100 million different types of antibodies that are required to protect us against a wide variety of invading antigens. Antibodies are proteins manufactured by B cells to fight against foreign substances, Antigens are substances that stimulate the immune system to produce antibodies.

innate immune system

humans are born with an innate immune system that is made up of a collection of both cellular and protein elements. This system provides both external and internal defenses against foreign invaders

exercise when already sick

if one has common cold symptoms, runny nose sore throat without fever or general body aches and pains, intensive exercise training may be safely resumes a few days after the resolution of symptoms, mild to moderate exercise when sick like walking with the common cold does not appear to be harmful, in 2 studies using nasal sprays of a rhinovirus leading to a common cold symptoms, subjects were able to engage in exercise during the course of the illness without any negative effects on severity of symptoms or performance capability, with symptoms of fever, extreme tiredness, muscle aches, and swollen lymph glands, 2 to 4 weeks should probably be allowed before resumption of intensive training

increased susceptibility to infection

increased exposure to pathogens, exercise-induced immune suppression, inadequate diet, mental stress, and lack of sleep

macrophages are deriveed from

monocytes and are locates in tissues throughout the body

complement system

numerous proteins produced in the liver that circulate in the blood in inactive form. When activated, they bind to the surface bacteria triggering a rapid series of events resulting in the binding of more and more complement proteins to the bacteria. This eventually forms a hole in bacteria so that phagocytes recognize it as a harmful agent and they serve as a chemoattractant to recruit more immune cells to the infection.

"open window"

only lasts between 3-20 hours post exercise and studies have shown that immune function between athletes and non-athletes is not different at rest, or 24 hours after an intense workout. So weeks of repeated intense workouts should not create a chronic state of immune depression

cellular components:

phagocytes and natural killer cells are specialized cells that are designed to attack and kill invading pathogens. Both are members of the leukocyte family of blood cels. Leukocytes (white blood cells) are a group of special cells designed to recognize and wipe out foreign invaders and form the second line of defense against foreign agents

immunity

refers to all of the mechanisms used in the body to protect against foreign agents. immunity results from well-coordinated immune system that consists of both cellular and chemical components that provide overlapping protection against infectious agents. This overlapping of immune system components is designed to ensure that these redundant systems are efficient in protecting the body against infection from pathogens (disease-causing agents) such as bacteria, viruses, and fungi

high intensity/long-duration aerobic exercise increases the risk of infection

studies support the concept that athletes engaged in intensive endurance training suffer a higher incidence of URTI compared to sedentary individuals of people engaged in moderate exercise.

what is 40-60% VO2 max?

sub-lactate threshold, moderate exercise. higher intensity= higher risk of infection

acquired immune system

the acquired immune system is composed of highly specialized cells and processes that prevent of eliminate invading pathogens. This adaptive immune response provides us with the ability to recognize and remember specific pathogens and to mount stronger attacks each time a repeating pathogen is encountered

cortisol

the biological explanation for the suppressed immune system is likely connected to the stress hormone cortisol. high cortisol levels have been reported to depress the immune system function. Specifically, high cortisol level can blunt the effect of cytokines, suppress natural killer cell function, and depress both the production and function of T cells

exercise and resistance to infection

the concept that exercise can have both a positive and negative effect on the risk of infection is almost 2 decades old

physical barriers

the skin and mucus provide a first line defense against bacteria and other invaders