Effects of Respiratory Yoga Training on Heart Rate Variability and Baroreflex of Healthy Elderly Subjects

Overview

The decreases of physiological capacities which take place with senescence include diminishing respiratory capacity as well as a reduction of heart rate variability and baroreflex sensibility. Altogether, these alterations increase elderly people's frailty and have a negative impact over quality of life. Since Yoga (Indian auto-discipline) has a wide range of respiratory exercises already investigated as components for non-pharmacological treatments for hypertension (situation in which heart rate variability is also diminished), the investigators hypothesis is that the training of respiratory exercises of Yoga may have a significant positive effect on heart rate variability and baroreflex of health elderly subjects, increasing quality of life and reducing frailty. We included 30 health elderly subjects (both sexes, from 60 years-old onwards) divided into 2 randomized experimental groups: control (C) and respiration (R). Each group underwent an entry evaluation, followed by a 4-months training period, after which they were re-evaluated. Control consisted of 2 stretching classes per week, and respiration consisted of 2 respiratory exercises classes a week. Both groups were instructed to perform the exercises at home twice a day, and to keep a record of each session in a log sheet. Evaluations were: WHOQOL-OLD questionnaire for quality of life, 20 minutes of seated rest with heart rate, respiration and blood pressure acquired continuously for further spectral analysis.

Heart rate variability was performed using the autoregressive model, and the baroreflex was calculated with the spontaneous approach, both with the softwares developed in Milan by Alberto Porta in a non-invasive way. The frequency domain analysis of heart rate, respiration and systolic blood pressure were conducted, consisting of calculating the power spectral density with the minimum error predicted by Akaike's algorithm. Spectral power was then subdivided into two bands of physiological interest: low - (LF 0.03-0.15 Hz) indicating predominant sympathetic modulation, and high - (HF 0.15-0.5 Hz) frequency, indicating parasympathetic modulation of the heart. The fraction calculated dividing LF by HF (LF/HF ratio) provided information of sympathovagal balance to the heart. The spectral analysis of Systolic Blood Pressure provided information of the vasomotor tone, and the integration of heart rate information with these data also provided information about the spontaneous baroreflex gain. Other questionnaires used were: Pittsburgh Quality of Sleep Questionnaire, Stress Symptoms Questionnaire by Marilda Lipp - validated in Brazil, and Beck's anxiety and depression inventories.