[The effect of exercise and elite athletics on the immune system]

Physical and psychological stress influence immune responses. The influence of physical stress on immunity is through the action of neuro-peptides and other hormones and by way of a direct effect on the cells controlling the immune response. There is little or no evidence that physical activity, i.e. regular exercise without competition has any harmful effects on immunity. On the contrary, some animal studies tend to indicate a beneficial effect of exercise on the immune system. Regular intense training and competitions have been associated with increased morbidity, especially from infections. This may be connected to suppression of cell-mediated and humoral immunity which has been demonstrated in connection with exercising to exhaustion.