The Effect of Exercise on Secretory and Natural Immunity

Abstract
The high frequency of recurrent respiratory infections following “overtraining” in competitive athletes prompted this study to examine the effects of intense prolonged exercise on mucosal immunoglobulins (Ig). In a previous study from this laboratory, it was shown that in elite athletes (US National Nordic ski team) resting salivary IgA levels are lower than in age-matched control subjects, and that IgA levels decrease further after two to three hours of exhaustive exercise (1981 US National Nordic ski competition) (1). It was unclear whether the decreases in IgA were due to the effects of exercise, to the effects of cold (1°C), to the stress of competition, or to a combination of factors. To further elucidate the role of exercise, we studied competitive bicyclists in a controlled environment and noncompetitive laboratory setting. We followed secretory Ig levels for two days after exercise in order to study the time course of suppression and return to baseline levels following cessation of exercise. In addition, we measured NK cytotoxic activity before and after exercise in order to study whether severe exercise alters other immune parameters.