Immunological effects of competitive versus recreational sports in cross-country skiing

For a period of two months during the competitive season the effects of end urance training in cross-country skiers were evaluated in order to compare the adaptive and innate immune systems between 10 competitive athletes, 10 moderately trained athletes and 10 untrained healthy controls. The main res ults were as follows: the peripheral T-lymphocyte count of the competitive athletes was decreased. In contrast the number of peripheral blood NK cells was increased in this group. These data imply a diminution of the adaptive immune system due to repeated bouts of intense exercise and contemporaneou s reinforcement of the innate immune response. Moreover the inducible IL-12 -expression following monocyte stimulation was significantly decreased in c ompetitive athletes. Compared with the other two groups, the moderately tra ined athletes showed a significantly increased production of IFN-gamma upon T-cell stimulation. These data suggest that the immune system may profit f rom moderate endurance training by an increased capacity to generate IFN-ga mma while the immune situation following repeated exhausting exercise of co mpetitive athletes tends to deteriorate through downregulation of IFN-gamma and IL-12.