Transcutaneous Electrical Nerve Stimulation of PC5 and PC6 Acupoints Increases Sympathovagal Balance but Not Oxidative Stress in Healthy Subjects: A Randomized Clinical Trial

Background: Transcutaneous electrical acupoint stimulation (TEAS) improves autonomic balance and reduces oxidative stress in subjects with chronic diseases, that decreases the risk of low-grade chronic inflammatory diseases, including cardiovascular diseases. However, these beneficial effects have never been demonstrated in healthy subjects. Objectives: To evaluate the acute effects of TEAS on autonomic balance and oxidative stress of healthy subjects. Methods: A randomized clinical trial was conducted with male healthy subjects (1830 years old), randomly allocated to control (no intervention; n = 14), placebo (placebo intervention; n = 14) and TEAS group (at PC5 and PC6 acupoints; n = 13). The protocol consisted of accommodation (20 min), intervention (40 min), and recovery (30 min) periods. The acute effects of TEAS on hemodynamics were studied through measurements of heart rate, blood pressure and double product; on the autonomic nervous system by assessing heart rate variability; and on oxidative stress by quantifying reactive oxygen species in saliva samples, collected at the end of each period. Results: TEAS increased heart rate and double-product compared to control and placebo groups (p < 0.01). Moreover, TEAS increased sympathetic and reduced parasympathetic tonus, increasing the sympathovagal balance compared to the control and placebo groups. However, TEAS exerted no effect on oxidative stress in saliva samples. Conclusion: In healthy subjects, TEAS at PC5 and PC6 acupoints acutely improved autonomic balance, increasing sympathetic and reducing parasympathetic tonus, reflecting little improvement on hemodynamic responses. Whether it could be used as a cardioprotective strategy remains uncertain since it exerted no effect on oxidative stress.