Neurophysiological effects of heart rate variability biofeedback training in adolescents: a Russian study
METHODS: A group of 15-16 years old adolescents with high sympathetic tone (Group I, n=24) and a group of adolescents of similar age, but with a normal sympathetic tone (n=22) participated in the study. HRVB sessions were carried out as specified in the patent N 2317771 RU). Every adolescent held 10 HRVB sessions. Electroencephalogram (EEG) was recorded at the first and at the tenth session of HRVB. Maximal amplitude and index in each frequency EEG-ranges (4-7 Hz, 8-12 Hz, 13-25 Hz) were performed. Paired data were compared using Wilcoxon sign rank test while independent data were compared by Mann-Whitney tests.
RESULTS: Higher baseline levels of the studied EEG parameters in adolescents with high sympathetic tone compared to adolescents with normal sympathetic tone (p for all tests <0.05) were observed at the first HRVB session. After the first session of HRVB, EEG alpha-activity increased in both groups (p for both tests <0.05) while systolic blood pressure decreased (p for both tests <0.05) as compared with baseline values. Adolescents with high sympathetic tone showed a reduction in theta-activity (p<0.05) while no changes were found in adolescents with normal sympathetic tone. After the tenth HRVB session all studied indices of EEG-activity in the group of adolescents with high sympathetic tone (all p<0.01) became comparable with the corresponding indices observed in the group of adolescents with normal sympathetic tone.
CONCLUSIONS: HRVB sessions have a potential for reduction of blood pressure and for optimization of the functional brain activity and increase of the stability of a subcortical brain structures regulation among adolescents with high sympathetic tone.