Aims: Salivary Immunoglobulin A is the most important part of immune system in upper respiratory tract. The findings of the studies regarding hormonal and immune changes, especially mucosal immune system, are highly contradictory and different. The purpose of this study was to compare the effect of intense exercise in the morning and evening on the concentration of salivary cortisol and Immunoglobulin A, in young swimmers.

Methods: This study is a quasi- experimental design conducting in 2010-11 academic years. The population of the study included 120 young boy swimmers, studying in a guidance school in Gonabad city, of which 20 were selected using random convenient sampling method. The subjects performed the selected exercise in two times, one on 11 in the morning and the other after 16 days. Saliva samples were taken before and immediately after the intensive exercise. The data were analyzed using SPSS 14 software by paired T-test.

 Results: A significant decrease of Immunoglobulin A was observed in the morning exercise. Likewise, a significant decrease in cortisol was seen in the evening exercise. The amount of swimmers’ salivary Immunoglobulin A and cortisol had a significant decrease after the exercise compared with before it (p=0.0001). Moreover, their amount in the evening turn had a significant decrease compared to the morning turn (p=0.0001).