Elite athlete training and immune system
There is both anecdotal and epidemiological evidence that regular moderate exercise reduces the risk of infections by having a positive effect on the immune system( Pacque, Booth, Ball, & Dwyer, 2007). Couple physiological factors and changes associated wit peak performance and relationship with elite athletic performance. Several studies have examined various physiological responses associated with the cardiorespiratory, metabolic, hormonal, neuromuscular and immunological systems during the pre-event taper across a number of sports (Mujika, Padilla, Pyne, & Busso, 2004).
Other studies discussed that exercise has a variable effect on the immune system and include infectious, neuroedocrine, and metabolic factors, with nutritional status of the athlete and the training load playing a role (Brollinson, & Elliott, 2007). Regular moderate exercise is associated with a reduced incidence of infection and prolonged bouts of strenuous exercise cause a temporary depression of various aspects of immune function (e.g., neutrophil respiratory burst, lymphocyte proliferation, monocyte antigen presentation) that usually lasts approximately 3-24 h after exercise, depending on the intensity and duration of the exercise bout (Gleeson,2007). Furthermore, inadequate or inappropriate nutrition can compound the negative influence of heavy exertion on immunocompetence.
Dietary deficiencies of protein and specific micronutrients have long been associated with immune dysfunction (Gleeson,Nieman, Pedersen, 2004).Although it is possible that immune depression linked with prolonged intensive training may determine susceptibility to infection, convincing evidence of a cause and effect relationship remains elusive (Gleeson, 2006).
Immune system and environment Factors
Intense exercise has been shown to impair natural killer cell activity and lymphocyte production postexercise and increase cytokine concentration. (Nielsen, 2003; Pedersen, & Toft, 2000). However, Pedersen, Rohde, & Zacho(1996) discussed that after exercise there is an “open window” period of impaired immunity, that the degree and duration of immunosuppression is related to the intensity and duration of exercise and that the risk of infection by viruses and bacteria is increased during this period. However, hormonal markers such as testosterone, cortisol, testosterone : cortisol ratio, 24-hour urinary cortisol : cortisone ratio, plasma and urinary catecholamines, growth hormone and insulin-like growth factor-1 are sometimes affected and changes can correlate with changes in an athlete’s performance capacity(Mujika, Padilla, Pyne, & Busso, 2004). Furthermore, an adequate intake of iron, zinc and vitamins A, E, B6 and B12 is particularly important for the maintenance of immune function, but excess intakes of some micronutrients can also impair immune function and have other adverse effects on health(Gleeson ,Nieman, & Pedersen, 2004).
Several studies indicate that the incidence of symptoms of upper respiratory tract illness is increased in the days following prolonged strenuous endurance events and it has been generally assumed that this is due to the temporary exercise-induced depression of immune function (Gleeson,2006). Therefore, environmental factors such as living quarters, travel requirements, and the type of sport (team versus individual) also contribute to infectious risk ( Brollinson, & Elliott, 2007).
Understanding the relationship between exercise and infectious disease has important potential implications for public health and for clinicians caring for athletes and athletic teams( Brollinson, & Elliott,2007). Although elite athletes are not clinically immune deficient, it is possible that the combined effects of small changes in several immune parameters may compromise resistance to common minor illnesses(Gleeson, 2006). Therefore, it is important to note that some or all of the described physiological and psychological changes associated with the taper occur simultaneously, which underpins the integrative nature of relationships between these changes and performance enhancement (Mujika, Padilla, Pyne, & Busso, 2004).
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