Yoga has received considerable attention for its potential therapeutic benefits over the past decades and it gradually became object of scientific scrutiny. There is currently extensive literature supporting its use as a non-pharmacological tool for managing a variety of medical problems. A few studies have also explored potential beneficial effects of practising yoga during pregnancy on maternal and neonatal outcomes. An association between prenatal yoga and decreased incidence of fetal growth restriction, preterm delivery, and labor abnormalities resulting in operative delivery have been reported. Exact mechanisms by which yoga could improve perinatal outcomes have not been elucidated yet. One of such mechanisms could be the positive effect of yoga on autonomic nervous system (ANS). Maternal cardiovascular system undergoes profound changes during pregnancy and ANS plays a central role in adaptation to pregnancy-related hemodynamic changes. Increase in peripheral vascular resistance that characterises hypertensive disorders in pregnancy with fetal growth restriction is mediated by substantial increase in sympathetic vasoconstrictor activity. Effects of yoga on ANS outside of pregnancy have already been investigated in several studies. Heart rate variability (HRV) indices, used as a one of proxy measures for ANS activity, showed significant shifts towards parasympathetic dominance following yoga sessions. Another objective means of assessing ANS activity is measurement of phase synchronisation between cardiovascular and respiratory systems following acute challenge. The higher the cardiorespiratory synchronisation after acute challenge is, the higher is the ability of ANS to flexibly adapt to challenge. The objectives of the study are: I. To examine whether there is a short-term shift in autonomic balance to the parasympathetic branch of the ANS and ability of the cardiovascular and respiratory respiratory systems to flexibly adapt to acute psychological challenge following sessions in pregnancy. II. To investigate potential long- term effects of yoga practice during pregnancy on HRV and cardio-respiratory synchronisation following acute psychological challenge.
Study Type
INTERVENTIONAL
Allocation
NON_RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
NONE
Enrollment
100
Weekly 90 min pregnancy-adapted yoga classes lead by certified yoga instructors.
20-30 min easy walking
UMC Ljubljana
Ljubljana, Slovenia
UMC Maribor
Maribor, Slovenia
Change in cardio-respiratory phase synchronisation index
Cardio-respiratory phase synchronisation index measures synchronisation between the cardiovascular and respiratory system following acute psychological challenge. It's value is between 0 (no synchronisation) and 1 (complete synchronisation). The higher the value, the higher the ability of cardiovascular and respiratory systems to flexibly adapt to challenge (standardised memory task).
Time frame: Change in cardio-respiratory phase synchronisation index from baseline (measured up to 30 minutes before yoga class/walk) to the end of exercise (measured up to 30 minutes after the end of yoga class/walk)
Change in LF/HF HRV ratio.
For frequency related HRV indices, we will run an autoregressive spectral analysis using Burg's algorithm (model order 24) after resampling and removing the trend of 2nd order. Low frequency (LF) will be defined as 0.04 - 0.15 Hz, high frequency (HF) will be defined as 0.15 - 0.40 Hz. The higher the LF/HF HRV ratio, the lower the parasympathetic tone.
Time frame: Change in LF/HF HRV ratio from baseline (measured up to 30 minutes before yoga class/walk) to the end of exercise (measured up to 30 minutes after the end of yoga class/walk).
BRS
The sequence technique will be used for the assessment of baroreceptor sensitivity (BRS). This technique is based on identifying consecutive cardiac beats in which an increase in systolic blood pressure is accompanied by an increase in heart rate, or in which a decrease in systolic blood pressure is accompanied by a decrease in heart rate. The regression line between the systolic blood pressure and heart rate produces an estimate of BRS. The higher the BRS, the higher the parasympathetic tone.
Time frame: Change in BRS from baseline (measured up to 30 minutes before yoga class/walk) to the end of exercise (measured up to 30 minutes after the end of yoga class/walk).
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