Background: The aim of this research was to determine the relationship between inflammatory markers (Fibrinogen, C-reactive protein (CRP) and Creatine kinase (CK)) and respiratory responses FEF25-75% (Forced expiratory flow in 25-75 percent) and FEV1 (Forced expiratory volume in one second) in 14-16 year’s Urmia city boys in response to an incremental physical activity.

Materials and Methods: The subjects were boys of 14-16 years among 24 healthy participants. These groups divided into two groups randomly, one group as trained one (n=12) and the othes as control group. Blood sample was taken in baseline and after Modified Balke Protocol in trained group, And the blood sampling was taken in baseline and 48 hours later in control group. respiratory responses were measured immediately after Modified Balke Protocol.

Results: CRP and Fibrinogen significantly increased in trained group (p<0.001) and this group had high level of these markers compared with control group (p<0.001). The association between CRP with FEF25-75% and fibrinogen with FEF %25-75 and CK with FEF 25-75% in trained group was significant (p&le0.05).

Conclusion: The results of this study show that incremental physical activity increased inflammatory factors in active children. Incremental exercise shows a strong relationship between some inflammatory markers and respiratory parameters in adolescents 14-16 years old.