EXERCISE IMMUNOLOGY - PRACTICAL APPLICATIONS

During the last 95 years, 629 papers (60% in the 1990s) dealing specif ically with exercise and immunology have been published. Major finding s of practical importance interms of public hearth and athletic endeav or include: (a) In response to acute exercise (the most frequently stu died area of exercise immunology), a rapid interchange of immune cells between peripheral lymphoid tissues and the circulation occurs. The r esponse depends on many factors, including the intensity, duration, an d mode of exercise, concentrations of hormones and cytokines, change i n body temperature, blood flow, hydration status, and body position. O f all immune cells, natural killer (NIK) cells, neutrophils, and macro phages (of the innate immune system) appear to be most responsive to t he effects of acute exercise, both in terms of numbers and function. I n general, acute exercise bouts of moderate duration (<60 min) and int ensity (<60% VO(2)max) are associated with fewer perturbations and les s stress to the immune system than are prolonged, high-intensity sessi ons. (b) In response to long-term exercise training, the only finding to date reported with some congruity between investigators is a signif icant elevation in NK cell activity. Changes in the function of neutro phils, macrophages, and T and B cells in response to training have bee n reported inconsistently, but there is some indication that neutrophi l function is suppressed during periods of heavy training. (c) Limited data suggest that unusually heavy acute or chronic exercise may incre ase the risk of upper respiratory tract infection (URTI), while regula r moderate physical activity may reduce URTI symptomatology. (d) Work performance tends to diminish with most systemic infections, and clini cal case studies and animal data suggest that infection severity, rela pse, and myocarditis may result when patients exercise vigorously. (e) Although regular exercise has many benefits for HIV-infected individu als, helper T cell counts and other immune measures are not enhanced s ignificantly. (f) Data suggest that the incidence and mortality Fates for certain types of cancer are lower among active subjects. The role of the immune system may be limited, however, depending on the sensiti vity of the specific tumor to cytolysis, the stage of cancer, the type of exercise program, and many other complex factors. (g) As individua ls age, they experience a decline in most cell-mediated and humoral im mune responses. Two human studies suggest that immune function is supe rior in highly conditioned versus sedentary elderly subjects. (h) Ment al stress, undernourishment, quick weight loss, and improper hygiene h ave each been associated with impaired immunity. Athletes who are unde rgoing heavy training regimens should realize that each of these facto rs has the potential to compound the effect that exercise stress is ha ving on their immune systems.