Objectives : This study was performed to examine the hypothesis that the structural imbalance affect cardiac function and autonomic reflex system and to investigate the possibility of the chiropractic care for cardiovascular system. Methods : 78 of Dong-Guk University students with structural imbalance were recruited for the investigation from March to June 2007. Heart rate variability, Buss and Durkee Hostility inventory(BDHI) and physical examinations to evaluate psoas muscle contracture were performed. Results : Left psoas muscle contracture was associated with decrease of LF/HF ratio(p=0.048). Conclusion : Left side contracture of psoas muscle showed a tendency to decrease sympathetic activity.