Effect of Hi-method for body regulation on heart rate and salivary cortisol level after stress reaction

Aim: To observe the effect of Hi-method for body and mind regulation on heart rate and salivary cortisol level response to stress reaction. Methods: The experiment was carried out in the Institute of Neuroinformatics, Laboratory of Body and Mind, Dalian University of Technology between May and June in 2006. Thirty-three healthy subjects (the 3rd-year Physics students of Dalian University of Technology, 22 males and 11 females, aging 19-21 years) volunteered for the study with their informed consents, and were randomly divided into two groups. 1 Hi-method treatment group (n=16) attended training for 5 days before stress test. Subjects practiced Hi-method while listening to the instruction and background music. The control group (n=17) did not receive any relax training during that period. 2 All subjects were given a 5-minute rest at the laboratory. We adapted the mental arithmetic task as the psychological acute laboratory stressor. Subjects were instructed to undergo a 3-minute serial subtraction task, afterwards the treatment group performed 20-minute Hi-method, whereas the control group quietly sat for 20 minutes. We repeatedly recorded the heart rate and collected saliva samples on the time points of baseline, right after stress task and 20 minutes after stress task. The salivary cortisol level was analyzed by radioimmunoassay. Results: All 33 students finished the experiments and entered the result analysis without any dropout. 1 The serial subtraction task successfully induced acute stress, the heart rate and salivary cortisol level significantly increased in the stress condition than at the baseline [Hi-method treatment group: (87.71±13.77, 71.50±10.28) beats/min, (10.13±3.64, 7.90±3.51) nmol/L; Control group: (84.12±14.30, 77.65±9.14) beats/min, (13.79±6.18, 10.03 ±4.01) nmol/L, P < 0.01]. 2 The heart rate on the time point of 20 minutes after stress task had no significant difference between two groups, both dropping to the level of baseline (P > 0.05). After 20-min Hi-method practice, the treatment group showed an significantly attenuated salivary cortisol level in comparison to controls (12.95±4.26, 17.58±7.48) nmol/L, t=2.130, P < 0.05]. Conclusion: The Hi-method effectively attenuates the excessive secretion of salivary cortisol and helps to maintain physiological as well as psychological equilibrium under stress.