Response of the cardiovascular system to heart rate variability biofeedback intervention in adolescents with different autonomic nervous tone living in northern and southern regions

BACKGROUND: The cardiovascular responses of adolescents during self-regulation are contingent upon their initial autonomic tone and place of residence. AIM: To investigate the dynamics of cardiovascular system indices during heart rate variability biofeedback (HRV BF) training in adolescents with different initial autonomic regulation of heart rhythm, taking into account their residence in the northern and southern regions. MATERIAL AND METHODS: Schoolchildren aged 1617 years, residents of the northwestern (n=55), northeastern (n=55) and southern (n=55) regions of the Russian Federation were examined. Heart rate variability (HRV) and blood pressure (BP) were recorded. Participants were divided into the following groups according to their baseline autonomic regulation of cardiac rhythm: vagotonics, normotonics and sympathotonics. Normotonics and sympathotonics additionally had a one-time HRV BF session to increase parasympathetic influences on heart rhythm. RESULTS: The northwestern/northeastern/southern samples revealed 29/7/16% vagotonics; 42/47/49% normotonics; and 29/46/35% sympathotonics. BP was significantly greater in sympathotonics compared to vagotonics and normotonics in in the northeastern region and sympathotonics in the northwestern and southern regions. HRV BF training was successful in all participants: HRV parameters responded to a greater extent in sympathotonics living in the northwestern region while their BP and baroreflex levels were relatively stable. Sympathotonics of the northeastern and southern regions were characterized by preservation of elevated HR after HRV BF accompanied by a significant decrease in BP and a pronounced baroreflex response. CONCLUSION: In the northwestern region, adolescents who are mainly decendants of migrants from the southern regions typically have sympathicotonia and increased vascular response to HRV BF. The descendants of natives of the northwestern region apparently inherited more advanced mechanisms of cardiovascular regulations in the conditions of the Arctic.