Exercise and Immunity

Abstract

It is generally accepted that moderate physical activity can improve immune functions and potentially reduce the risk of developing infectious diseases and cancer. There is accumulating evidence to show that moderate physical activity can enhance the activities of T cells, natural killer cells and macrophages, cytokine productivity and serum immunoglobulin (Ig) G and salivary IgA levels. In contrast, however, exhaustive exercise causes the systemic release of immunosuppressive stress hormones and anti-inflammatory cytokines, and temporarily causes a decrease in circulating lymphocyte counts and the reduction in activities of T cells and natural killer cells and salivary IgA levels. Consequently, these negative alterations in immune function and cytokine imbalance may enhance host susceptibility to infections and promote allergic disposition. Although exercise-induced mobilization and activation of phagocytic cells such as neutrophils and monocytes can result in muscular, vascular and systemic inflammation and oxidative stress due to the production of reactive oxygen species, these deleterious responses may be attenuated by the appropriate use of antioxidants and nutritional supplements. This review presents the findings from recent studies in the field of exercise immunology, and offers some insight into how these findings may be applied in the broad realm of preventive, complementary and alternative medicine.