Introduction: Cardiovascular diseases are the most common cause of death in the most countries and Iran, and are the main disability cause, those induced stress, anxiety and changes in vital signs in patients with myocardial infarction. This study was conducted to determine the effect of progressive muscle relaxation on the vital signs of patients with myocardial infarction.

Methods: In the randomized double-blind clinical trial, 66 patients with myocardial infarction after sampling by convenience method, randomly selected and assigned by random allocation method to 33 patients either the control or intervention groups. An orientation session was held to explain the research goals and intervention. The test group did the progressive muscle relaxation technique, two 20-30 minutes sessions daily for 2 months (120 sessions). Data collection tools were demographic information questionnaire, vital signs record and self report check lists. Independent sample t-test, U Mann Whitney, repeated measure analysis of variance, and Friedman tests were used.

Results: Pulse and respiratory rate variables between intervention group )P<0.048) (P<0.001(and also systolic blood pressure over the three times (Pre, one and two months after intervention) between control and intervention groups had showed significant differences (P<0.001). Moreover, pain variable over the two times post intervention between control and intervention groups had demonstrated significant differences (P<0.001).

 Conclusion:  Applying progressive muscle relaxation technique would modify, adjust and improve various aspects of vital signs of patients suffering myocardial infarction.

Keywords: Myocardial infarction; Progressive muscle relaxation; Vital Signs.