Purpose of review: To evaluate the effects of exercise on immune function in relation to infection susceptibility.
Recent findings: Postexercise immune function depression is most pronounced when exercise is continuous, prolonged, of moderate to high intensity and performed without food intake. Periods of intensified training that result in overreaching have been shown to chronically depress immune function, with leukocyte functions measured at rest still depressed 24 h after the last exercise bout. 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. More recently it has been proposed that at least some of these symptoms are attributable to inflammation of the upper respiratory tract rather than to infectious episodes.
Summary: 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. 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.