Natl. J. Physiol. Pharm. Pharmacol. (2025), Vol. 15(1): 69–75

Original Research

10.5455/NJPPP.2025.v15.i1.12

Objective evaluation of effects of different yoga techniques based on recording of electrical and mechanical activity of the heart

Sowjanya T.^1*, Sai Dinesh Thatikonda² and Balakrishna Nagalla³

¹Department of Physiology, Apollo Institute of Medical Sciences and Research, Hyderabad, India

²Department of Orthopaedics, Shadan Institute of Medical Sciences, Hyderabad, India

³Department of Statistics, Apollo Institute of Medical Sciences and Research, Hyderabad, India

*Corresponding Author: Dr Sowjanya T. Assistant Professor. Department of Physiology, Apollo Institute of Medical Sciences and Research, Hyderabad, India. Email: sowjanya.gdss [at] gmail.com

Submitted: 23/11/2024 Accepted: 03/12/2024 Published: 31/01/2025

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Abstract

Background: Research into cardiovascular changes during yoga is crucial for validating its health benefits, enhancing personalized care, and supporting global health strategies.

Aim: In this context, the present study investigates the immediate effects of Balasana, Viparita Karani, and Apan Vayu Mudra on both cardiac electrical and mechanical activity, contributing to a deeper understanding of yoga’s impact on cardiovascular health.

Methods: The study was conducted in the year 2024 among 30 healthy students, aged 18 to 25 years who were selected through a simple random sampling technique. Each participant performed all three yogic techniques in a single session, with heart rate (HR), blood pressure (BP), and heart rate variability (HRV) recorded at baseline, during, and after the practices using a digital sphygmomanometer (OMRON) and the ADInstruments PowerLab26T Teaching System. Statistical analysis was performed using repeated measures ANOVA and Friedman’s two-way ANOVA.

Results: Both Balasana and Viparita Karani elicited significant increases in systolic and diastolic blood pressures during the posture, with values returning to baseline during recovery, while heart rate exhibited a similar pattern of elevation followed by recovery. In contrast, Apan Vayu Mudra did not result in significant changes in blood pressure. However, it induced an increase in HR during mudra compared to the resting phase. Additionally, a decrease in HFnu and an increase in LFnu and the LF:HF ratio was observed during the mudra, relative to resting values.

Conclusion: Our study demonstrates the immediate effects of yogic techniques sustained over 5 minutes, highlighting differential cardiovascular responses. These findings contribute to a deeper understanding of yoga’s benefits and may help prevent potential adverse effects by promoting more informed practice.

Keywords: Balasana, Viparita Karani, Apan Vayu Mudra, HR, BP.

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Introduction

Yogic practice has been integral to Indian culture for centuries, with ancient Indians diligently practicing it. Yoga integrates physical postures (asanas), pranayama, hand gestures (mudras), and meditation, collectively promoting holistic improvement in physical, mental, emotional, and spiritual well-being (Iyengar, 1976; Vandali and Biradar, 2018). Yoga and its health benefits have recently garnered significant attention from professionals, especially researchers, alongside an expanding global initiative to scientifically examine its physiological effects (Dutta et al., 2022; Yatham et al., 2023; Sengupta, 2012). Among the diverse physiological effects of yoga, its influence on the cardiovascular system has been the subject of extensive research (Isath et al., 2023; Kalra et al., 2022).

The cardiovascular system is intricately regulated by the autonomic nervous system (ANS), which maintains homeostasis and adapts to the body’s changing demands. The cardiac autonomic nervous system (CANS) is crucial for maintaining cardiac function, including heart rate (HR), systolic blood pressure (SBP), and diastolic blood pressure (DBP) (Gordan et al., 2015). Different yogic techniques elicit varied physiological responses, even within a single short session. For example, lateral shifts, forward bending, backward bending, prone poses, and breathing duration variations lead to distinct changes in BP and HR, primarily mediated by autonomic nervous system regulation (Bhavanani et al., 2014; Malhotra, 2005; Pramanik et al., 2009). In the last few years, heart rate variability (HRV) has been established as a non-invasive tool to evaluate CANS function (Sztajzel et al., 2004). High HRV typically signifies optimal autonomic adaptability, while low HRV is commonly linked to various health conditions, including cardiovascular disorders such as hypertension, ischemia, sudden cardiac death, and heart failure (Tiwari et al., 2021). The underlying mechanisms of autonomic functioning during yoga are less studied compared to the post-intervention effects of yoga, which have shown improvements in HRV with sustained practice (Tyagi and Cohen, 2016). The paucity of research and the variability in findings regarding the immediate effects of yogic techniques provided the impetus for this study. To investigate these effects, we selected two asanas and one mudra: Balasana (a forward-bend pose), Viparita Karani (an inversion pose), and Apan Vayu Mudra. Our goal was to advance the scientific understanding of these yogic techniques by evaluating their effects on the cardiovascular system, including the electrical component through HR and HRV in the frequency domain, and the mechanical component through blood pressure measurements.

Materials and methods

This was a cross-sectional study that employed a pre- and post-intervention design. The experiment was conducted in the Electrophysiology Lab in the Department of Physiology at Apollo Institute of Medical Sciences and Research, Hyderabad in the year 2024 between April and June. Ethical clearance was obtained from the Institutional Ethics Committee (EC/NEW/INST/1527/2023/09/138). The study was conducted on 30 healthy students from the Apollo College of Nursing and Apollo College of Physiotherapy between the ages of 18 to 25 years who were recruited by simple random sampling. Written informed consent was obtained from all subjects who were enrolled after briefing them about the study protocol. Subjects with cardiovascular, respiratory illness, or other systemic illnesses, smokers, alcoholics, and regular yog practitioners were excluded from the study.

The parameters measured were HR, SBP, DBP, and HRV. HR and BP were measured using a digital sphygmomanometer (OMRON) which has instrumental accuracy of ± 5% for HR and ± 3 mm Hg for BP. HRV was evaluated using a Lead II Its Electrocardiogram. (ECG) with the AD Instruments PowerLab 26T Teaching System. Following the guidelines established by the Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology (1996), a minimum of 5 minutes of ECG recording was analyzed to accurately quantify sympathetic and parasympathetic activity.

Study design

The study was conducted over a 12-week period. Participants were assessed on separate days to ensure precision in data collection. All experimental sessions took place between 8:00 AM and 10:00 AM to standardize timing. Participants were instructed to arrive in a fasting state and to wear loose, comfortable attire to minimize interference during assessments. The laboratory environment was carefully controlled, with subdued lighting, a quiet atmosphere, and a comfortable temperature to facilitate participant relaxation.

The primary parameters viz. HR, SBP, DBP, and HRV were measured at three intervals: prior to, during, and following the practice of each specific yogic technique, namely Balasana [B.A.], Viparita Karani [V.K.], and Apan Vayu Mudra [A.V.M.].

Data collection

Prior to initiating data collection, participants were instructed to rest in a supine position for 10 minutes to establish a stable baseline. The study design, represented schematically in Figure 1, was followed consistently across all sessions. To prevent carry-over effects of ANS modulation, sufficient intervals were maintained between different yogic techniques. Apan Vayu Mudra was performed in a seated posture, as this position is optimal for its efficacy.

Procedural guidelines for each yogic technique Balasana [B.A.]

1. Assume a kneeling position with feet positioned together, ensuring that the big toes are in contact.
2. Allow the buttocks to rest on the heels while gently tucking the tailbone inward.
3. Inhale deeply, and as you exhale, lower the upper body forward until the forehead contacts the floor, maintaining alignment of the spine and neck with the crown of the head directed forward.
4. Extend the arms forward with palms facing down.
5. Relax the neck and shoulders, allowing the torso to expand with each inhale and exhale.
6. After holding the pose for 5 minutes, release by returning to the initial seated position.

Viparita Karani [V.K.]

1. Position yourself seated on a mat near a wall, with one hip close to the wall.
2. Gently lower yourself onto your back, simultaneously raising your legs up against the wall in a fluid motion.
3. Adjust the body position so the buttocks rest comfortably near the wall.
4. Extend the legs vertically along the wall, keeping them straight but relaxed without locking the knees.
5. Place the arms by the sides with palms facing upward.
6. Close the eyes, directing attention to the breath.
7. Maintain the pose for 5 minutes.
8. To exit the pose, bend the knees, roll to one side, and rise to a seated position gradually.

Apan Vayu Mudra [A.V.M.]

1. Sit in a comfortable, upright position with a tall spine.
2. Extend both arms forward with palms facing upward.
3. Bend the index finger to touch the base of the thumb.
4. Place the thumb over the index finger.
5. Bring the tips of the thumb, middle, and ring fingers together.
6. Extend the little finger outward.
7. Maintain straight elbows (full extension).
8. Close the eyes and focus on a calm, steady breath.

Fig. 1. The schematical representation of study design.

Data analysis

Data were assessed using SPSS version 24. Data pertaining to HR and BP changes before, during, and after yogic techniques for different techniques was analyzed using repeated measures of ANOVA as they passed normality testing by the Kolmogorov Smirnov Test. HR and BP were reported as means and standard deviations. However, Data pertaining to Frequency domine indices of HRV were tested using Friedmann two-way ANOVA as the variables did not follow a normal distribution pattern. Frequency domain indices were reported as median and interquartile range (IQR). The following frequency-domain indices were obtained viz. 5 min Total power ms² (The variance of NN intervals over the temporal segment, Note: NN-intervals refer to the intervals between normal R-peaks), LF ms² (Power in the low-frequency range: 0.04–0.15 Hz), LF norm n.u. (LF power in normalized units), HF ms² (Power in high frequency range: 0.15–0.4 Hz), HF norm n.u. (HF power in normalized units) and LF:HF ratio. Under resting conditions, the LF band in HRV primarily reflects baroreflex-mediated autonomic regulation involving both sympathetic and parasympathetic activity, rather than being a direct measure of cardiac sympathetic innervation (Goldstein et al., 2011). The HF band in HRV reflects parasympathetic activity via respiratory sinus arrhythmia but not exclusively cardiac vagal modulation (Grossman and Taylor, 2007).

The LF:HF ratio was once considered a marker of sympathovagal balance, but it is now controversial due to its dependence on complex autonomic interactions, baroreflex activity, and measurement conditions (Shaffer and Ginsberg, 2017).

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Results

Table 1 presents the characteristics of the study participants.

The changes in SBP, DBP, and HR over time across different yogic techniques are summarized in Table 2. Tables 3–5 show the changes in frequency domain indices over time for Balasana, Viparita Karani, and Apan Vayu Mudra, respectively.

Table 1. Demographic profile of the participants.

Table 2. SBP, DBP, and HR change over time in Balasana, Viparita Karani, and Apan Vayu Mudra.

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Discussion

Scientific exploration of the physiology of yoga is essential to validate its traditional wisdom and promote its acceptance in modern medicine. Our study aimed to investigate the cardiovascular effects of three yogic techniques—Balasana, Viparita Karani, and Apan Vayu Mudra—by analyzing heart rate, blood pressure, and heart rate variability before, during, and after practice, and to correlate changes in HRV with alterations in blood pressure and heart rate.

Balasana

In our study, SBP and DBP increased significantly during the Balasana posture compared to the baseline values, with minimal variation between initial and 5-minute measurements within the posture. Upon transitioning to a supine recovery position, both SBP and DBP significantly decreased, returning to baseline values, with no notable changes over the subsequent 5-minute recovery period. HR also increased significantly during Balasana compared to resting values and decreased significantly by the 5-minute mark within the posture. During recovery, HR continued to decline significantly at both 1- and 5-minute intervals in the supine position. However, HRV in our study showed no statistically significant changes across the observed periods. These findings differ from those reported by Ahmad Rufa’i et al. (2013), who observed a significant reduction in SBP and DBP within 1 minute and an increase in pulse rate at 1 and 3 minutes of entering the head-down crooked kneeling (HDCK) posture, a position closely resembling Balasana (Ahmad Rufa’i et al., 2013). The discrepancy may reflect differences in populations, with our study involving yoga-naïve participants and their habitual practitioners with potential baroreceptor adaptations. Interestingly, significant reductions in SBP, DBP, and HR were observed among students who practiced Balasana consistently for three months, as reported in a study, highlighting the benefits of sustained practice, which we hypothesized might also be evident during a single 5-minute session (Jabir et al., 2017).

Viparita Karani

In Viparita Karani, both SBP and DBP showed a significant increase compared to baseline values, though no substantial differences were observed between the initial and 5-minute measurements within the posture. Following the posture, SBP and DBP significantly decreased upon transitioning to a supine recovery position and remained stable during a 5-minute recovery period. HR also increased significantly in Viparita Karani compared to resting values, with a notable decrease by the 5-minute mark within the posture. During recovery, HR did not show a significant decrease at the 1-minute mark but did reduce significantly by the 5-minute mark. Using a comparable approach to explore cardiopulmonary physiology, one study found a significant decrease in HR and DBP but no change in SBP when transitioning from standing to supine to the inversion pose (Viparita Karani). This contrasts with our findings, with the discrepancy likely attributable to baroreceptor adaptation in their subjects, who were experienced yoga practitioners (Seffens and Seffens, 2020). Intriguingly, a study on yoga practitioners reported a decrease in LF and an increase in HF during inversion postures like Sarvangasana, which is closely related to Viparita Karani. However, we did not observe any significant changes in HRV either during or after the pose (Pitale et al., 2014).

Table 3. Changes in the median and interquartile range (IQR) of frequency domain indices over time in Balasana.

Table 4. Changes in the median and IQR of frequency domain indices over time in Viparita Karani.

Apan Vayu Mudra

Mudras, a simple and accessible form of yoga, have garnered increasing research interest due to their ease of practice and minimal risk of adverse effects compared to more complex yogic techniques like asanas and pranayama. It is hypothesized that hand mudras stimulate nerve endings, enhance parasympathetic activity, and promote autonomic balance, potentially aiding cardiovascular stability even during emergencies. Numerous studies have emphasized the health benefits of yoga for individuals with asthma, hypothyroidism, cardiovascular diseases, or anxiety disorders, even with short durations of practice (Anu et al., 2019; Tripathi et al., 2016, 2018; Saraswat and Kumar, 2021). Among these, Apan Vayu Mudra, also known as the “V Mudra,” has been recognized for its potential to alleviate symptoms in cardiac patients. For instance, Tripathi et al. demonstrated significant reductions in BP and HR in hypertensive individuals following a single 15-minute session of this mudra (Seffens and Seffens, 2020). Another study reported substantial decreases in SBP and DBP after three consecutive days of 5-minute daily practice among hypertensive subjects (Sunitha and Sharma, 2020). In contrast, our study conducted on healthy individuals did not observe significant changes in either SBP or DBP after a 5-minute practice of the mudra. HRV analysis during the mudra and recovery phases showed a significant decrease in HFnu, suggesting possible vagal withdrawal, alongside an increase in LFnu, reflecting sympathetic augmentation. These changes were supported by an increase in HR compared to baseline values. The divergence in results may be attributed to differences in study populations, with our research focusing on healthy participants, while previous studies have involved hypertensive individuals. Our study’s strengths include its consistent timing (8:00 AM to 10:00 PM) and the use of a standardized yoga protocol with adequate intervals to prevent carryover effects. The inclusion of both male and female participants enhances the generalizability of the findings. Comprehensive measurements taken before, during, and after each practice address the limitations of prior studies that focused on only one phase. Additionally, the study offers novel insights into the cardiac autonomic effects of three distinct yogic techniques. However, the study’s limitations include the lack of a three-armed design involving the same participants and a yoga-experienced group. This was due to logistical constraints, such as participants’ reluctance to attend consecutive sessions, which hindered a direct comparison of autonomic modulation between yoganaïve individuals and experienced practitioners.

Table 5. Changes in the Median and IQR of frequency domain indices over time in Apan Vayu Mudra.

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Conclusion

In conclusion, our study demonstrates that Balasana,

Viparita Karani, and Apan Vayu Mudra elicit distinct autonomic responses in healthy individuals, with observed changes in blood pressure and heart rate but no significant alterations in heart rate variability. These results suggest that the effects of these practices may depend on participants’ health status and prior yoga experience. Future research should explore longer practice durations, include diverse populations (e.g., experienced practitioners), assess the cumulative effects of repeated sessions, and examine the impact of performing these asanas immediately post-exercise to better understand their role in post-exercise recovery and autonomic regulation.

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Acknowledgment

We extend our deepest gratitude to the students of the Apollo College of Nursing and Apollo College of Physiotherapy for their invaluable cooperation and dedicated participation, which were essential to the successful completion of this research.

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Statement of funding

No funding was received for this study.

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Conflicts of interest

The authors have no conflicts of interest to disclose.

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Authors’ contributions

All authors contributed equally to the conception and design of the study, the acquisition and analysis of data, and the drafting and revision of the manuscript.

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Data availability

The data that support the findings of this study are available from the corresponding author, (Sowjanya T), upon reasonable request.

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