TRAINING LOAD AND DECREASED FITNESS LEVELS

A SPELL OF ILLNESS MEANS A REDUCED

THE IMMUNE SYSTEM Our immune system can be split into two parts – innate immunity and adaptive immunity. The innate system is our primary defence, which if breached is then backed up by the adaptive system. With so many bacteria, viruses and other infectious agents existing in the environment, we need both systems to be working optimally to ensure that we do not become ill.

The innate immune system This is composed of both biochemical and physical defences. These defences include, among other things, mucus, stomach acid, sebaceous gland secretions and gut organisms. Various cells, called phagocytes, are derived from bone-marrow stem cells; their role is to surround infectious particles that penetrate through the skin and other external barriers and then to destroy them. Another key proponent of the innate immunity is the natural killer (NK) cells, which help to reject any cells that have been virally infected. NK cells recognise changes in cells that are virally infected, which enables the NK cells to attach to and kill the infected cells. Just as with an injury during sport, inflammation is a response to infection. While we bring oxygen and glucose to the muscles during exercise with increased blood flow, so we also must bring immune activity to sites of inflammation. Leucocytes and macrophages are attracted to sites of inflammation in order to combat infection. Phagocytes, after recognising infectious agents, can then surround and destroy them.

The adaptive immune system This is based around the activity of antibodies and lymphocytes. Antibodies are produced by the B-lymphocytes of the adaptive immune system. The role of antibodies becomes more prominent when phagocytes cannot recognise infectious cells: antibodies then provide a link between the infectious cells and the phagocytes. These antibodies are flexible adaptors that can bind to

specific locations on infectious cells called antigens and neutralise them.

THE LYMPHATIC SYSTEM The lymphatic system has an important role in immune system function as well as functioning to absorb excess fluids and return it to the bloodstream and to aid in the absorption of fat. The lymphatic system has capillaries throughout the body, much like vessels of the circulation system, and some 600–800 lymph nodes. Contractions of skeletal muscle help to move the lymph fluid around the body.

There are four main lymph organs: (i) the lymph nodes, which contain concentrated numbers of lymphocytes and macrophages; (ii) the spleen, which filters the lymph fluid and blood that passes through it; (iii) bone marrow, which produces lymphocytes, monocytes and leucocytes; and (iv) the thymus gland. The lymph system has a key role in distributing B-cells, which produce antibodies and helper T-cells, which are developed in the thymus. These cells are paramount in aiding the combat of infection if the inflammation response from the damaged cells has not done enough to neutralise the microbes. The immune system is called into play at this point to supplement the inflammatory response. The immune system not only brings essential cells to fight infection to specific sites throughout the body but also acts as a way for the debris from injury and infection to be cleared away and then filtered by the spleen.

HORMONAL MODULATION OF IMMUNITY

It is important to remember that the inflammation response is induced by the immune system to combat pathogens, invading biological agents that cause illness or disease. A cold, sore throat or fever are the symptoms of the body expelling the pathogens casuing the infection of trying to expel infection from the body. This inflammatory response is not caused solely by invading pathogens, as

SYSTEM AND TRAINING CAN DECREASE IMMUNITY

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THE LYMPHATIC SYSTEM HAS AN IMPORTANT ROLE IN IMMUNE

sportEX dynamics 2009;21(Jul):7-9