Investigating components of pranayama for effects on heart rate variability

Abstract

Objective: Traditional Indian breath control practices of Pranayama have been shown to increase indices of heart rate variability (HRV) that are generally held to reflect parasympathetic nervous system (PNS) tone. To our knowledge, individual components of pranayama have not been separately evaluated for impact on HRV. The objective of this study was to isolate five components of a pranayama practice and evaluate their impact on HRV.

Methods: In a crossover clinical trial, 46 healthy adults were allocated to complete five activities in random order, over five separate visits: 1) sitting quietly; 2) self-paced deep breathing; 3) externally-paced deep breathing; 4) self-paced Sheetali/Sheetkari pranayama; and 5) externally paced Sheetali/Sheetkari pranayama RESULTS: Our final sample included 25 participants. There was a significant increase in a time-domain index of HRV, the root mean square successive differences between RR intervals (RMSSD), during the five interventions. The change in logRMSSD ranged from 0.2 to 0.5 (p < .01 in all conditions by paired t-test). Greater increases were evident during externally-paced breathing than during self-paced breathing (mean pre-during logRMSSD change of 0.50 vs. 0.36, p = .02) or sitting quietly (mean, 0.17 ms; p = .005 and 0.02 when comparing Activities 3 and 5 to Activity 1 by random intercept model with Tukey correction for multiple comparisons). Lastly, pre-during increase in RMSSD was greater for Sheetali/Sheetkari vs. deep breathing, when controlling for respiration rate, though not significantly different (p = .07 in random intercept model) CONCLUSIONS: RMSSD increased with paced breathing, deep breathing, and Sheetali/Sheetkari pranayama, reinforcing evidence of a physiologic mechanism of pranayama.

Trial registration: NCT03280589 https://www.clinicaltrials.gov/ct2/show/NCT03280589?term=sheetali&draw=2&rank=1.

Keywords: Autonomic nervous system (ANS); Blood pressure; Heart rate variability (HRV); Pranayama; Respiratory rate; Sheetali.

Conflict of interest statement

Conflicts of Interest: All authors have completed the Unified Competing Interest form. The authors have no competing interests to report.

Copyright © 2021 Elsevier Inc. All rights reserved.

Figures

Figure 1.

Illustration of Sheetali and Sheetkari pranayamas, involving inhaling through an open mouth (rolled tongue, Sheetali; exposed teeth, Sheetkari) and exhaling through the nose.

Figure 2.

Recruitment for our study, detailing numbers assessed for eligibility and enrolled, as well as those who completed visits and were analyzed.

Figure 3.

Respiratory rate (y-axis) during eight 5-minute steps (x-axis) at each of five visits/breathing activities (Activities 1-5, indicated by colored lines). Activity 1 was Sitting Quietly, Activity 2 was Deep Breathing (self-paced), Activity 3 was Deep Breathing (externally-paced), Activity 4 was Sheetali and Sheetkari (self-paced), and Activity 5 was Sheetali and Sheetkari (externally paced). Steps 1 & 2 are baseline/ pre-intervention measurements, in Steps 3-6 the breathing activity for the visit is administered per the randomization sequence, and Steps 7-8 are post-intervention measurements. For Sheetali and Sheetkari interventions, Sheetali took place during Steps 3-4 and Sheetkari took place during Steps 5-6. Error bars represent ± 1 SE.

Figure 4:

Mean respiratory rate (breaths per minute, b/min) over time (pre, during, and post breathing activities) for each intervention (Activities 1-5). Activity 1 was Sitting Quietly, Activity 2 was Deep Breathing (self-paced), Activity 3 was Deep Breathing (externally-paced), Activity 4 was Sheetali and Sheetkari (self-paced), and Activity 5 was Sheetali and Sheetkari (externally paced). *P0.05 (not significant). Error bars represent standard error.

Figure 5.

Box and Whisker plots of variability in mean respiratory rate (breaths per minute, b/min) at baseline (A); and during each intervention, Activity 1-5 (B). The grey box represents interquartile range. The dark, solid line represents the median. The lowest and tallest lines represent minimum and maximum values, respectively.

Figure 6.

Log of the root mean square of successive normal RR intervals (RMSSSD, y-axis) during eight 5-minute steps (x-axis) at each of five visits/breathing activities (indicated by colored lines). Steps 1 & 2 are baseline/ pre-intervention measurements, in Steps 3-6 the breathing activity for the visit is administered per the randomization sequence, and Steps 7-8 are post-intervention measurements. Breathing activities are defined as follows: Activity 1: Control/ Sitting quietly/ Normal breathing; Activity 2: Deep Breathing (self-paced); Activity 3: Deep Breathing (externally-paced); Activity 4: Sheetali/Sheetkari Breathing (self-paced); Activity 5: Sheetali/ Sheetkari Breathing (externally-paced). Error bars represent ± 1 standar error (SE).

Figure 7.

HRV parameters over time (pre, during, post intervention) during each intervention (Activities 1-5) represented in terms of: (A) log of the root mean square of successive normal RR intervals (RMSSD); (B) log of the standard deviation of all normal RR intervals (SDNN); and (C) log of high-frequency (HF) heart rate variability. *P<0.05, ** P<0.01, ***P<0.001, NS P>0.05 (not significant). Error bars represent confidence intervals.