Although the terms "exercise" and "heart health" are practically synonymous, members of The International Society of Exercise and Immunology (ISEI) are accustomed to looking at the effects of exercise on a deeper level. The ISEI recently issued a position statement on immune function and exercise that covers many aspects of exercise (eg, exercise and respiratory infection, cellular function, and inflammation).1 The following are highlights:
• The investigators differentiate between "exercise" and "physical activity." The term "exercise" implies activity for the specific purpose of competing or improving physical condition. Because of this distinction, as well as an emotional component, exercise is likely to have a greater effect on the immune system than physical activity.
• Exercise-induced immune suppression increases susceptibility to infection, especially around the time of a competition, evidence suggests. Much more information is needed about whether exercise-induced changes in immune function alter susceptibility to infection and whether the anti-inflammatory effects of exercise are mediated through exercise-induced effects on innate immune cells.
• Lymphocytosis occurs during and immediately after exercise and is proportional to the extent and intensity of the activity. The number of T cells and B cells dips below pre-exercise levels during early recovery but returns to normal within 24 hours.
• T- and B-cell activity differs in sedentary versus athletic persons. Activity is somewhat blunted in sedentary persons but sensitive to training load increases in athletes. Changes include reduced T-cell proliferation and enhanced B-cell immunoglobulin synthesis; the changes appear to be related to increased levels of circulating stress hormones and changes in pro- and anti-inflammatory cytokines.
• Information about the effects of exercise on dendritic cells is scant.
• Exercise alters measures of immunity by 15% to 25%. Whether this affects host defense or disease susceptibility or severity mechanisms remains to be determined.
• Exercise has anti-inflammatory effects, including an increase in at least 2 circulating anti-inflammatory cytokines: interleukin (IL)-1 receptor antagonist and IL-10. More study is needed to determine the type of exercise that most effectively alleviates the inflammation that underlies so many chronic diseases.
The paper is available for download at http://www.isei.dk/services/download.php?url=../files/eir/eir17.pdf.
1. Walsh NP, Gleeson M, Shephard RJ, et al. Position statement, part 1: immune function and exercise. Exerc Immunol Rev. 2011;17:6-63.