Objective To investigate the change in the content of intracellular adhesion molecule-1(ICAM-1)in myocardium of rats at different time courses after exhausted exercise.Methods One hundred male SD rats were divided into sedentary control group,single bout of exhausted exercise group and 14-day consecutive exhausted exercise group.Rats were killed at 0.6,1 2 and 24 hours after exhausted exercise.Immunofluorescence technique and image analysis method were used to study the dynamic changes in the content of ICAM-1 in myocardium.Results Comparing with the control group,following these 2 modes of exhausted exercise,the content of ICAM-1 in rat myocardium increased and reached its peak value 6 hours after exercise,and then decreased,and ICAM-1 content in all other time courses were significantly increased(P<0.01)after exhaustive exercise,except 24h after exercise group (P>0.05).ICAM-1 content from different parts of myocardium immediately after consecutive exhausted exercise was significantly higher than that after single bout of exhausted exercise (P<0.01),and the differences disappeared 6 hours after exercise(P>0.05).ICAM-1 content in 12-and 24-hour single bout of exhausted exercise groups was significantly higher than that in consecutive exhausted exercise groups(P<0.01).Conclusion The increase of ICAM-1 level in myocardium after difierent modes of exhausted exercise can activate cytokine,mediate inflammatory responses of myocytes,such as adhesion and infiltration,which contribute to the exercise-induced myocardial micro-injury.