Exercise is one of the important factors in the prevention, treatment and maintenance of mental and physical health. The immune system is one of the vital systems, the proper functioning of which guarantees the health of individuals. The aim of this study is to investigate the effect of strength exercises on the immune system's performance of athletes in the bodybuilding clubs of northern Tehran in 2012. The study is a randomized-clinical trial, in which 96 athletes from northern Tehran were surveyed in 2012. Demographic data and disease history was collected through a researcher-made questionnaire; for this purpose, the subjects were divided into two groups, with each group including 48 subjects; one group was made to do regular exercises ...