Yoga Practitioners Exhibit Higher Parasympathetic Activity and Baroreflex Sensitivity and Better Adaptability to 40 mm Hg Lower-Body Negative Pressure.

Yoga has been shown to improve autonomic conditioning in humans, as evidenced by the enhancement of parasym-pathetic activity and baroreflex sensitivity. Therefore, we hypothesized that the experience of yoga may result in adaptation to acute hemodynamic changes. To decipher the long-term effects of yoga on cardiovascular variability, yoga practitioners were compared to yoga-naïve subjects during exposure to -40 mm Hg lower-body negative pressure (LBNP). A comparative study was conducted on 40 yoganaïve subjects and 40 yoga practitioners with an average age of 31.08 ± 7.31 years and 29.93 ± 7.57 years, respectively. Heart rate variability, blood pressure variability, baroreflex sensitivity, and correlation between systolic blood pressure and RR interval were evaluated at rest and during LBNP. In yoga practitioners, the heart rate was lower in supine rest (p = 0.011) and during LBNP (p = 0.043); the pNN50 measure of heart rate variability was higher in supine rest (p = 0.011) and during LBNP (p = 0.034). The yoga practitioners' standard deviation of successive beat-to-beat blood pressure intervals of systolic blood pressure variability was lower in supine rest (p = 0.034) and during LBNP (p = 0.007), with higher sequence baroreflex sensitivity (p = 0.019) and ~ high-frequency baroreflex sensitivity. Mean systolic blood pressure and RR interval were inversely correlated in the yoga group (r = -0.317, p = 0.049). The yoga practitioners exhibited higher parasympathetic activity and baroreflex sensitivity with lower systolic blood pressure variability, indicating better adaptability to LBNP compared to the yoga-naïve group. Our findings indicate that the yoga module was helpful in conditions of hypovolemia in healthy subjects; it is proposed to be beneficial in clinical conditions associated with sympathetic dominance, impaired barore-flex sensitivity, and orthostatic intolerance.

The Cardiovascular Variability during Transient 6° Head Down Tilt and Slow Breathing in Yoga Experienced Healthy Individuals.

OBJECTIVE: The intervention of yoga has been shown to improve autonomic conditioning in humans and better adaptability to orthostatic challenges. Similarly, slow breathing at 0.1 Hz akin to pranayama also increases baroreflex sensitivity (BRS). Hence, we intended to investigate whether yoga practitioners have different autonomic responses at rest,during slow deep breathingas well as during 6° head down tilt (HDT) compared to naive group individuals. AIM: The aim of the study was to evaluate the acute effects of slow breathing on cardiovascular variability during HDT in yoga practitioners compared to yoga-naïve individuals. SETTINGS AND DESIGN: This was a comparative study with repeated measures design conducted in Autonomic Function Test lab of the Department of Physiology, All India Institute of Medical Sciences, New Delhi, India. MATERIALS AND METHODS: Time domain and frequency domain parameters of heart rate variability, blood pressure variability (BPV), and BRS were evaluated during 6° HDT and slow breathing at 0.1 Hz on forty yoga-naïve individuals and forty yoga practitioners with an average age of 31.08 ± 7.31 years and 29.93 ± 7.57 years, respectively. All of the participants were healthy. STATISTICAL ANALYSIS USED: General Linear Mixed Model ANOVA was applied with yoga experience as a between-group factor in repeated measures. Independent sample t-test was applied for between group comparison of respiratory rate, demographic, and anthropometric data. P <0.05 is considered statistically significant. RESULTS: Between-group comparison during HDT with spontaneous breathing has shown a significantly lower heart rate (P = 0.004) with higher RR interval (RRI) (P = 0.002) and pNN50% (P = 0.019) in yoga practitioners. The sequence BRS (P < 0.0001) and α low frequency (LF) of spectral BRS (P = 0.035) were also significantly higher in the yoga group compared to the naïve group. Similarly, during HDT with slow breathing, the heart rate was lower (P = 0.01); with higher RRI (P = 0.009); pNN50% (P = 0.048). Standard deviation of successive RR interval difference of systolic BPV was lower (P = 0.024) with higher sequence BRS (P = 0.001) and α LF of spectral BRS (P = 0.002) in yoga group than naïve group. CONCLUSION: The yoga experienced individuals exhibit higher resting parasympathetic activity, lower systolic BPV, and higher BRS than naïve to yoga individuals. It is inferred from the findings that yoga practitioners were better adapted to transient cephalad fluid shift that happens during 6° HDT. Furthermore, acute slow breathing during 6° HDT reduced the systolic blood pressure in all the participants suggesting the beneficial role of slow breathing during exposure to extreme conditions such as microgravity which might help in the prevention of adverse effects of cephalad fluid shift during long-term weightlessness and maintain the astronaut health. Future mechanistic studies with active yoga intervention are necessary to understand the adaptive mechanisms involving central and vascular modulations contributing to either attenuation or accentuation of the cardiovagal baroreflex during HDT and slow breathing in healthy individuals.

Autonomic Tone and Baroreflex Sensitivity during 70° Head-up Tilt in Yoga Practitioners.

INTRODUCTION: The intervention of yoga was shown to improve the autonomic conditioning in humans evident from the enhancement of parasympathetic activity and baroreflex sensitivity (BRS). From the documented health benefits of yoga, we hypothesized that the experience of yoga may result in adaptation to the orthostatic stress due to enhanced BRS. AIM: To decipher the effects of yoga in the modulation of autonomic function during orthostatic challenge. MATERIALS AND METHODS: This was a comparative study design conducted in autonomic function test lab, of the Department of Physiology, All India Institute of Medical Sciences, New Delhi, India. Heart rate variability (HRV), blood pressure variability, and BRS were analyzed on forty naïve to yoga (NY) subjects and forty yoga practitioners with an average age of 31.08 ± 7.31 years and 29.93 ± 7.57 years, respectively. All participants were healthy. Seventy degrees head up tilt (HUT) was used as an intervention to evaluate the cardiovascular variability during orthostatic challenge. RESULTS: During HUT, the R-R interval (P = 0.042), root mean square of succesive R-R interval differences (RMSSD) (P = 0.039), standard deviation of instantaneous beat-to-beat R-R interval variability (SD1) (P = 0.039) of HRV, and sequence BRS (P = 0.017) and α low frequency of spectral BRS (P = 0.002) were higher in the yoga group. The delta decrease in RRI (P = 0.033) and BRS (P < 0.01) was higher in the yoga group than the NY group. CONCLUSION: The efferent vagal activity and BRS were higher in yoga practitioners. The delta change (decrease) in parasympathetic activity and BRS was higher, with relatively stable systolic blood pressure indicating an adaptive response to orthostatic challenge by the yoga practitioners compared to the NY group.

Effect of slow breathing on autonomic tone & baroreflex sensitivity in yoga practitioners.

BACKGROUND & OBJECTIVES: Slow breathing increases parasympathetic activity and baroreflex sensitivity (BRS) in healthy individuals, also similarly observed in yoga practitioners. Pranayama which is an important component of yoga when practiced at a slow pace was at a respiratory frequency of around 0.1 Hz (6 breaths/min). Therefore, it was hypothesized that yoga practitioners might have adapted to slow breathing. This study was aimed to decipher the role of yoga on cardiovascular variability during slow breathing (0.1 Hz) in yoga practitioners. METHODS: A cross-sectional study was undertaken in naïve-to-yoga individuals (n=40) and yoga practitioners (n=40) with an average age of 31.08 ± 7.31 and 29.93 ± 7.57 yr, respectively. The analysis of heart rate variability, blood pressure variability (BPV) and BRS during spontaneous and slow breathing was compared between the two groups. RESULTS: During slow breathing, the heart rate (P<0.01) was lower, respiratory rate interval (P<0.05) and pNN50 per cent (P=0.01) were higher, mean systolic BP (SBP) (P<0.05) and SDSD (Standard deviation of successive beat to beat systolic blood pressure differences) (P<0.01) of SBP variability were lower with sequence BRS (P<0.001) and α low frequency (P<0.01) and α high frequency (P<0.001) of spectral BRS were higher in yoga practitioners. INTERPRETATION & CONCLUSIONS: The present study indicated higher parasympathetic activity and BRS with lower SBP variability at rest and during slow breathing in yoga practitioners compared to naive group. Findings indicate that the short-term practice of slow breathing complements the augmented parasympathetic activity and BRS in the yoga group.