Infection, Immunity, and Exercise

Abstract

In brief How-and if-exercise alters immunity is open to debate. Research centers on changes in the number and function of granulocytes and lymphocytes and in levels of immunoglobulins. In general, these immune changes are mixed, mild, and brief. Clinical studies are inconclusive and fraught with confounders, especially the impact of psychological stress. Whether exercise enhances immunity or impairs it may, in fact, depend on whether the exercise is a joy or a stress.

Exercise and febrile illnesses

“…This may be due, in part, to effects on the immune system, but may also be related to other factors, such as psychological stress, inadequate recovery time and fatigue (2). It is also recognized that exercising during an infectious illness may exacerbate symptoms, prolong the length of illness and increase the risk of potentially serious complications such as myocarditis (1,4,5).…”

“…The ratio of CD4 (helper T) to CD8 (suppressor T) cells also decreases, which may contribute to infection susceptibility. The salivary immunoglobulin A concentration is suppressed with shortterm exercise, and may even be diminished below baseline with long-term, high-intensity exercise (1)(2)(3)(4).…”

“…An infected athlete should attempt to exercise at mild to moderate intensity for 10 min to 15 min; if symptoms worsen, the athlete should stop and rest. If symptoms do not worsen, the athlete can continue to participate (3)(4)(5).…”

“…Once recovered, athletes should ease back into sports gradually, taking one to two days for every training day missed to build back up to preillness levels (3)(4)(5).…”

“…In general, decisions about whether to continue exercising during an illness can be made using a 'neck check' (3)(4)(5). If symptoms are confined to above the neck, such as a runny nose, nasal congestion or sore throat, athletes may continue to participate as long as they feel able.…”