Effect of Tai Chi on Cardiac Autonomic Function and Salivary Cortisol Level in Healthy Adults

Introduction: An estimated 8.2 million American adults (1 in 3) have 1 or more types of cardiovascular disease. Heart rate variability (HRV) analysis is considered a non-invasive procedure for analyzing cardiovascular autonomic influence. Depressed HRV has been linked to stress and abnormal cardiovascular autonomic modulation.;Purpose: This study evaluated the acute effects of tai chi on cardiac autonomic function and cortisol level in healthy adults.;Design: 10 healthy adults, 7 females and 3 males, with an average age of 54 +/- 2.04 were included in this study. They were asked not to consume any alcoholic or caffeinated beverages at least 24 hours before the study. Each subject practiced tai chi for 1 hour. HRV measurements were obtained at supine rest using Nexus biofeedback device before and after 10 min, 20 min and 30 min post tai chi exercise. Saliva samples were collected before tai chi and after 45 min post tai chi practice.;Results: The cardiac autonomic function was assessed using frequency domain HRV analyses. Repeated measures ANOVA revealed that there is significant difference in means of HR, SDNN, nLF and nHF between the pre tai chi and post tai chi groups. Using student's T-test, we found that the nHF increased significantly from 42.79 +/- 4.12 to 52.82 +/- 4.39 after 30 min post tai chi exercise (p<0.05). In contrast, nLF decreased significantly from 57.21 +/- 4.12 to 52.82 +/- 4.39 after 30 min post tai chi exercise (p<0.05). HR significantly decreased from 73 +/- 2 to 67.79 +/- 2.94 after 30 min post tai chi exercise. Also, SDNN increased significantly from 34 +/- 5.26 to 41.38 +/- 6.42 after 30 min post tai chi exercise. No significant changes in cortisol level were observed between pre tai chi and post tai chi groups.;Conclusion: Tai chi exercise can modulate cardiac autonomic tone by enhancing the vagal activity and reducing the sympathetic activity. Long-term beneficial effects of tai chi on cardiac autonomic function need further investigation.