Effect of strenuous physical stress on circulating lymphocyte number and function before and after training.

Seventeen young male subjects underwent a six-week training period and their physical fitness was examined using a bicycle ergometer test. Twelve subjects without any marked training served as controls. Venous blood was drawn immediately before and after exercise on a bicycle ergometer both before and after training. After exercise, the subjects developed a leukocytosis as well as lymphocytosis where the proportion of E-rosettes, theophylline resistant E-rosettes and SIg-positive cells remained stable but their absolute number rose by more than 100% before training and more than 50% after training. In spite of the rise of immunocompetent cells in the circulation, the post exercise increase of lymphocyte transformation was not more than 10% both before and after training. After training the response to physical stress is manifested by a significantly weaker mobilization of lymphocytes into the circulation than before training. Consequently, when physical fitness is high fewer immunocompetent cells are required to produce a normal immune response than when physical fitness is low. Our findings indicate that in healthy individuals improved physical fitness compensates for the influence of stress on the immune system.