Abstract
Background
Mantra recitation is a universal practice that involves repeating sacred words or phrases. It is widely acknowledged for its function in improving concentration, slowing down thought processes and causing a variety of psychophysiological changes. Yet, no research has methodically looked at how various Mantra recitation techniques affect physiological parameters.
Purpose
This study was aimed to evaluate heart rate variability (HRV), autonomic function and respiratory variables prior to, during and following each style of Mantra recitation.
Materials and Methods
This trial involved 40 male novices between the ages of twenty and 25 years. The autonomic and respiratory variables of each participant were recorded before, during and following loud chanting (LC), lips movement chanting (LMC), silent chanting (SC) and no chanting (NC) in four distinct laboratory sessions. HRV frequency and time–domain measurements were taken from electrocardiogram (ECG) recordings, and data were obtained using a 16-channel polygraph. This study employed the repeated measures analysis of variance (RM ANOVA) to compare the differences between and within groups under the four conditions.
Results
Based on frequency domain measurements, the results showed a significant decrease in high-frequency (HF) power (p < .001) and a significant increase in low-frequency (LF) power (p < .001) during LC. Furthermore, NN50 was significantly higher (p < .001) in all sessions and groups, while pNN50 was significantly lower (p < .001) as compared to NC during LC. Moreover, the mean HR was considerably higher during LMC and LC (p < .001).
Conclusion
These results imply that, although in a relaxed physiological state, the LC and LMC styles of Mantra recitation may improve attentional focus while overdriving sympathetic activity. Nevertheless, vagal tone remained intact throughout the entire duration of the SC recitation.
Keywords: Mantra recitation, autonomic functions, heart rate variability
Introduction
Yoga is a holistic practice with deep spiritual roots that originated in ancient India and is guided by a set of organised beliefs. It includes a broad spectrum of established mental, spiritual and physical disciplines meant to help people achieve inner peace and self-realisation. Among these techniques, reciting Mantras (Japa) has long been thought to be an effective way to improve mental and physical health, especially when done during meditation. 1
An instrument that aids in achieving stillness and transcending mental fluctuations is symbolised by the term ‘Mantra’, which is derived from the Sanskrit roots ‘Man’, which means mind, and ‘Tra’, which means instrument or vehicle. Repetition of sacred words or phrases is a technique used in many spiritual traditions around the world to control thoughts and attain intense focus. 2 According to Newberg et al. (2001) chanting repeatedly has been linked to improved autonomic stability, decreased stress levels and increased cognitive functions. 3
Mantras are useful focal points in meditation that promote emotional equilibrium and mental clarity, much like visual symbols or objects. Their physiological and psychological effects are well-supported by scientific research, and they are widely used in both traditional and modern Yoga practices. 4 There are three distinct styles of mantra chanting, each with its unique significance for the body and mind. These styles include Manasika Japa, also known as silent chanting (SC); Vaikhari Japa or loud chanting (LC); lips movement chanting (LMC); and Upamshu Japa, which involves whispered or humming repetition. 5
In Yogic literature, ‘Om’ is one of the most well-known Mantra. It is a primordial sound that is thought to resonate with universal consciousness. Research has shown that reciting ‘Om’ during meditation causes an increase in skin resistance, 6 and a decrease in heart rate (HR), 7 indicating a state of increased mental alertness and physiological relaxation. Chanting ‘Om’ has also been demonstrated to activate brain regions linked to autonomic and emotional regulation in functional magnetic resonance imaging (MRI) studies. 8
Similarly, to promote profound relaxation and mental clarity, transcendental meditation (TM) uses customised Mantras. According to studies on TM, it dramatically lowers blood lactate levels, oxygen consumption, breath rate and HR. It also shows a shift towards parasympathetic dominance and improved autonomic stability.9, 10 Slow alpha and theta wave activity have been found to increase in electroencephalogram (EEG) recordings, which is associated with heightened awareness and a calm mental state. 11
The benefits of Mantra recitation on physiological functions, especially cardiovascular regulation, have been further supported by scientific research. Mantra chanting improves cardiovascular rhythm synchronisation, which leads to better autonomic balance and stress resilience, according to research. 12 Reciting the rosary prayer at a regulated pace of six breaths per minute produced positive physiological effects, such as increased heart rate variability (HRV), a well-known indicator of cardiovascular health and emotional stability, according to a noteworthy study by Bernardi and colleagues.
One of the most venerated Vedic hymns, the Gayatri Mantra, has been demonstrated to improve memory and attention in particular. A study by Pradhan and Derle (2012) reported that participants who recited the Gayatri Mantra exhibited significantly improved attention performance compared to those who recited a standard poem, suggesting that structured Mantra repetition promotes neural efficiency. 13 Mantra meditation can also be used as an adjunct intervention for mental health disorders because it has been associated with decreased symptoms of depression and anxiety. 14
The evidence presented here suggests that reciting particular Yoga Mantras and prayers at predetermined frequencies has both psychological and physiological benefits. Since no research trials have been conducted to study the physiological effects of different styles of Mantra chanting, this study aims to assess autonomic and respiratory functions following various styles of Mantra chanting.
Materials and Methods
Subjects
In this study, 40 male novices with ages ranging from 20 years to 25 years (mean age ± SD: 21.3 ± 3.8) took part. The study was limited to male participants only because autonomic balance changes during menstruation. 15 All of the participants had little prior experience performing Vedic recitation, which they did for an hour every day, four days a week, for three years while enrolled in Yoga classes at a residential Yoga centre in southern India. A clinical examination verified their overall good health, and none of them had a history of smoking, drinking alcohol or consuming caffeinated beverages. Furthermore, none were taking any medications or engaging in any other wellness practices. ECG recordings confirmed that none of the participants had extrasystoles. All participants received a comprehensive explanation of the study’s design, and written informed consent was obtained. The Institutional Ethical Committee gave its approval to the study.
Study Design
Every participant took part in four distinct evaluation sessions in the lab; the sequence of these sessions was determined by a random number table. Participants underwent the following conditions on various days: (a) SC, or mentally repeating a Mantra for eighteen rounds; (b) verbal recitation of the Mantra; (c) whispering of the Mantra; and (d) silent sitting while observing recurring thoughts. Pre-recording, during and post-recording—each phase lasting ten minutes—made up the half-hour session. Recordings started at 9:45 AM following preparation, which included affixing sensors to different body parts. Participants arrived at the lab at 9:30 AM. A constant acoustic level of 85 dB was maintained in the lab, and all recordings were made with the room temperature at 25°C.
A schematic representations of the recruitment of the subjects and the sessions randomised for each of them on different days are given in Figure 1.
Figure 1. Figure Illustrating the Recruitment Process and Random Allocation of Participants During the Trial.
Assessments
Participants were seated comfortably during all assessments, which were held in a soundproof room. The study employed a 16-channel polygraph (Finapres Medical Systems, USA) to record autonomic and respiratory variables. Using conductive gel and Ag/AgCl electrodes, ECG data was recorded in a standard limb lead II configuration. A sampling rate of 1 kHz was used for data acquisition, and only noise-free data were used for offline analysis. A volumetric pressure transducer was positioned around the trunk, about 8 cm below the lower costal margin, while the subjects were standing up straight to measure their respiratory rate. The ECG’s QRS complex’s R waves were used to calculate the HR. A beat-to-beat heart series was created for analysis by identifying successive R waves.
Intervention
Mantra recitation, or Japa, is the practice of repeating a selected word, phrase or syllable while passively tuning out external and internal distractions. Although the terms used for concentration or meditation may change, the goal of the study is always the same. In Manasika Japa (SC), vocalisation is not used; instead, mental repetition is used. Known as Vaikhari Japa (LC) is a verbal repetition that muffles outside noises. LMC is combined with whispered or humming repetition is called Upamshu Japa (4). In a control session, participants also sat in silence and noted their impromptu thoughts (no chanting, NC). In this study, there were four different intervention conditions: (a) Manasika Japa, which involved silently reciting the Maha Mrityunjaya Mantra for 18 rounds over ten minutes; (b) Vaikhari Japa, which involved reciting the mantra aloud; (c) Upamshu Japa, which involved whispering or humming repetition; and (d) NC, which involved participants remaining silent and observing their own thoughts for ten minutes. All the three styles of mantra chanting were supervised by a Yoga instructor for 15 days as part of an orientation. Following this, participants were given a seven-day period for detraining, after which the immediate effects of the three styles of mantra chanting were assessed in the laboratory.
Data Extraction
To determine HR (beats per minute), QRS complexes were continuously counted throughout 60-second intervals. By counting breath cycles in 60-second intervals, the breath rate (cycles per minute) was calculated. Measurements of HRV were made for ten minutes each before, during and after the intervention. HRV time-domain parameters were analysed in compliance with the guidelines of the European Society of Cardiology. These included the total index of NN intervals (TINN), the number of normal-to-normal (NN) RR intervals that differed by more than 50 ms (NN50), NN50 divided by the total number of NN intervals (pNN50). A Fast Fourier transform (FFT) was used to analyse the HRV power spectrum in order to evaluate the energy distribution across three distinct frequency bands: high frequency (HF, 0.15–0.50 Hz), low frequency (LF; 0.05–0.15 Hz), and very LF (0.0–0.05 Hz). The normalised units for both HF and LF values were used. 16 For offline analysis, BP signals were digitalised at 100 Hz using Beat-Scope 1.1 (TNO - Netherlands organization for Applied Scientific Research).
Data Analysis
SPSS 22.0 was used to conduct statistical analyses. Parametric tests were used since the data was discovered to be normally distributed. The four conditions were compared using a one-way analysis of variance (ANOVA) to compare differences within and between groups.
Results
The HRV spectrum’s time-domain, frequency-domain, HR and breath-rate group mean values ± SD are shown in Table 1. ‘Mantra’ was evaluated both within and between groups using repeated measures ANOVA (RM ANOVA). Four groups (LC, SC, LM and NC) and three states (pre, during and post) were included in the study. A Bonferroni-adjusted post-hoc test was used after RM ANOVA to examine differences between the groups and states.
Table 1. Mean ± SD Scores of the Measures of Autonomic and Respiratory Variables in Various Phases of Mantra Chanting Across the Styles of Chanting.
| Variables | Lips Movement Chanting (LMC) | Loud Chanting (LC) | No Chanting (NC) | Silent Chanting (SC) | ||||||||
| Pre | During | Post | Pre | During | Post | Pre | During | Post | Pre | During | Post | |
| Mean RR | 806.37 ±126.68 |
753.11*** ±159.31b |
827.60* ±126.62 |
826.08 ±124.05 |
731.32*** ±95.79b |
850.66** ±119.37 |
874.76 ±155.73 |
878.50 ±150.19 |
884.36 ±136.11 |
823.23 ±130.22 |
808.04 ±126.99 |
830.99 ±118.68 |
| STDRR | 58.50 ±26.50 |
56.83 ±20.93 |
60.38 ±27.95 |
73.63 ±29.14 |
74.60 ±27.13 |
72.43 ±28.81 |
59.50 ±18.91 |
60.46 ±20.59 |
68.18 ±37.47 |
65.98 ±21.11 |
64.93 ±24.84 |
65.18 ±23.35 |
| Mean HR | 76.62 ±11.98 |
80.17*** ±11.79b |
74.54* ±11.13 |
74.75 ±11.28 |
84.33*** ±11.35b |
72.37** ±9.56 |
70.94 ±12.06 |
70.46 ±11.28 |
69.84 ±10.66 |
76.09 ±13.25 |
76.58 ±12.45 |
74.23* ±11.06 |
| STDHR | 5.35 ±1.68 |
5.69 ±1.21 |
5.22 ±1.73 |
6.71c ±2.30 |
8.03*** ±2.23c |
6.12 ±1.94 |
4.90 ±1.21 |
4.99 ±1.40 |
5.35 ±2.14 |
6.19 ±1.84 |
6.08 ±1.59 |
6.47 ±4.06 |
| RMSSD | 43.85 ±30.25 |
39.19 ±24.33 |
46.23 ±28.24 |
60.06 ±32.06 |
52.89 ±27.65 |
61.66 ±35.46 |
49.91 ±25.06 |
49.80 ±23.65 |
55.71 ±32.95 |
55.79 ±28.03 |
56.06 ±34.52 |
58.24 ±31.44 |
| NN50 | 65.63 ±57.05 |
115.17*** ±102.18 |
71.37 ±60.66 |
110.66 ±55.13 |
153.31*** ±97.08 |
101.56 ±56.50 |
85.96 ±57.11 |
176.18*** ±110.07 |
91.50 ±54.51 |
99.34 ±57.51 |
199.52*** ±112.26 |
108.93 ±66.11 |
| pNN50 | 18.86 ±18.36 |
16.17 ±16.28 |
21.27 ±19.75 |
31.89 ±18.51 |
19.61*** ±14.31 |
29.94 ±19.16 |
26.72 ±19.48 |
27.00 ±18.12 |
28.85 ±19.11 |
28.26 ±17.88 |
28.37 ±16.91 |
31.24 ±19.95 |
| RRINDEX | 14.09 ±6.08 |
14.56 ±4.80 |
354.74 ±1,868.92 |
16.30 ±4.85 |
16.83 ±5.25 |
15.55 ±4.25 |
13.55 ±3.19 |
15.19 ±4.26 |
14.17 ±3.38 |
15.16 ±3.64 |
15.55 ±4.09 |
14.71 ±4.16 |
| TINN | 239.00 ±71.39 |
262.00 ±74.23 |
230.83 ±78.73 |
277.81 ±74.39 |
341.41 ±72.78c |
268.44 ±74.99 |
214.64 ±79.45 |
235.36 ±99.64 |
227.50 ±71.19 |
290.86 ±83.45 |
295.17 ±85.28a |
290.86 ±110.12a |
| LF/HF | 1.56 | 1.69 | 1.63a | 1.13 | 2.38 | 1.01 | 0.86 | 1.08 | 0.95 | 1.07 | 1.11 | 1.02 |
| VLF | 38.74 ±14.59 |
36.96 ±16.01c |
34.91 ±19.28 |
30.85 ±15.70 |
21.85*** ±12.75a |
34.59 ±13.71 |
35.28 ±18.03 |
37.74 ±12.13 |
34.68 ±16.09 |
31.19 ±16.25 |
27.20 ±11.07 |
29.32 ±14.67 |
| LF (n. u.) | 60.97 ±19.11 |
62.85 ±12.62 |
62.01 ±20.32 |
53.18 ±17.90 |
70.43*** ±16.73c |
51.72 ±18.87 |
46.25 ±17.97 |
52.05 ±17.89 |
48.86 ±19.46 |
51.81 ±16.03 |
52.69 ±21.12 |
50.70 ±18.67 |
| HF (n. u.) | 39.03 ±19.11 |
37.15 ±12.62 |
37.99 ±20.32 |
46.82 ±17.90 |
29.57*** ±16.73c |
48.28 ±18.87 |
53.75 ±17.97 |
47.95 ±17.89 |
51.14 ±19.46 |
48.19 ±16.03 |
47.31 ±21.12 |
49.30 ±18.67 |
Note: ap < .05, bp < .01, cp < .001, comparison was made between NC and the other groups using ANOVA – between groups. RMSSD: Root mean square of the successive differences; STDRR: Standard deviation of RR intervals; STDHR: Standard deviations of HR intervals.
*p < .05, **p < .01, ***p < .001, comparison was made within groups using ANOVA (baseline was compared with ‘Pre’ and ‘Post’).
Post-hoc Analyses (RM ANOVA)
Frequency Domain Measures
Low Frequency: Within-group comparisons revealed that LF scores were significantly higher during LC (p < .001) compared to the pre- and post-LC states. Similarly, between-group comparisons showed a significantly higher LF level during LMC (p < .001) compared to NC and LC, with a significant increase (p < .05) during NC as well. Figure 2 illustrates the LF scores across all conditions and sessions.
Figure 2. The Mean Scores of LF During LC, Compared to SC, LM and NC.
High Frequency: HF was significantly higher during LC (p < .001) than it was before and after LC, according to within-group analysis. Significantly higher HF levels during LC (p < .001) than NC were also revealed by between-group comparisons. Figure 3 presents the HF scores of all conditions and sessions.
Figure 3. The Mean Scores of LMC and LC Compared to NC and SC.
LF/HF Ratio: There were no notable variations in the (LF/HF) ratio when comparing groups within the same group. But compared to pre, during and post-NC states, LF/HF was significantly higher after LMC (p < .05).
NN50: All sessions showed a significantly higher NN50 score (p < .001) than the corresponding pre- and post-session values within each group. There were no discernible variations between the sessions. The NN50 scores of all the conditions and sessions are shown in Figure 4.
Figure 4. Comparison of NN50 Scores (Pre, During, and Post) Across Different Chanting Conditions: Lip Movement Chanting (LMC), Loud Chanting (LC), No Chanting (NC), and Silent Chanting (SC).
pNN50: Compared to pre- and post-LC states, a significantly lower pNN50 score was noted during LC (p < .001). Between sessions, no discernible changes were observed. The pNN50 scores of all conditions and sessions are illustrated in Figure 5.
Figure 5. Comparison of PNN50 Scores (Pre, During, and Post) Across Different Chanting Conditions: Lip Movement Chanting (LMC), Loud Chanting (LC), No Chanting (NC), and Silent Chanting (SC).
STD (RR): There were no discernible variations in STD (RR) between groups or sessions.
STD (HR): Compared to pre- and post-LC states, within-group analysis revealed a significantly higher STD (HR) (p < .001) during LC. Comparing groups also showed that during LC, the STD (HR) was significantly higher (p < .001) than during NC.
RMSSD: After any session, no discernible changes were seen between or within groups.
TINN: Within groups, no discernible changes were found. In contrast to NC, TINN was significantly higher during LC (p < .001). Furthermore, a noteworthy rise was noted during SC in contrast to NC (p < .05) and after SC in contrast to post-NC (p < .05).
Discussion
In frequency-domain measurements, the current study found that during LC, LF power was higher, and HF power was lower. Furthermore, pNN50 was lower during LC than during NC, whereas NN50 was significantly higher throughout all sessions in all four groups. Additionally, during LMC and LC, mean RR and HR were noticeably higher, indicating a potential change in autonomic modulation.
According to a recent study by Nivethitha et al. (2017), practicing Bhramari Pranayama (the humming sound that occurs after inhaling) significantly increases HR and LF power of the HRV spectrum while significantly decreasing HF power. 17 Our study also revealed a significant increase in mean HR and LF power during LM and LC, along with an increase in pNN50 during LC and NN50 throughout all sessions, which is consistent with these findings.
In addition to a lower HF trend and an elevated LF trend, the observed higher mean HR trend during LM and LC points to increased sympathetic activation. Even though sympathetic dominance is present, a slight shift towards vagal activity is indicated by the consistently higher NN50 across all sessions across groups, suggesting a state of relaxation. On the other hand, the decreased pNN50 during LC indicates heightened sympathetic activation, supporting the idea that LM and LC cause sympathetic arousal while relaxation is taking place. Both frequency-domain and time-domain measurements are commonly used to analyse HRV. The LF component is influenced by both sympathetic and parasympathetic factors, whereas the HF component is primarily linked to parasympathetic (vagal) activity in the frequency domain. 18 According to Pal et al. the LF/HF ratio is a measure of sympathovagal balance. 19 The main factor influencing the mean RR interval in time-domain measures is vagal activity.20, 21
Several studies have looked at how different meditation techniques affect HRV. Practitioners of zazen meditation showed greater sympathetic activity and decreased cardiac vagal tone, as evidenced by increased LF power, decreased HF power, and a decreased LF/HF ratio. 22 TM research, on the other hand, revealed higher HR power, indicating improved parasympathetic (vagal) modulation.23, 24 Defocused meditation has also been linked to higher vagal tone and decreased sympathetic activity. Telles et al. pointed out that different meditation techniques have different autonomic reactions. 25
Neurophysiological Correlates of Sympathetic Activation During Mantra Recitation
Increased sympathetic activity, which is mainly mediated by the locus coeruleus–noradrenergic (LC–NA) system, is closely associated with attention. An essential brain centre for arousal and attentional processing is the LC, which is situated in the dorsal pontine tegmentum. 26 The LC–NA system is essential for controlling behaviours linked to stress and anxiety,27, 28 and is in charge of distributing noradrenaline (NA) throughout the central nervous system, which improves sensory processing, attention and memory. Thus, elevated attentional engagement, which is regulated by the LC–NA system, may be connected to the increased sympathetic activity seen during LM and LC.
Strengths and Limitations
The fact that this study included inexperienced male participants who had never heard the Maha Mrityunjaya Mantra recited before allowed for a controlled evaluation of its immediate physiological effects, which is one of its main advantages. Although there were a few limitations in this study, the major ones were the exclusion of female participants and the use of a ‘self-as-control’ design. Additionally, other objective variables, such as EEG and biochemical parameters, were not included due to funding constraints
Future Directions
For future research to validate these findings, a larger sample size and a longitudinal study design with four study arms should be used. Furthermore, combining a wider variety of respiratory and autonomic parameters with functional brain imaging (fMRI) may offer a more profound understanding of the neurophysiological processes underlying these autonomic changes during Mantra recitation.
Conclusion
Based on the observed results, it can be concluded that while the aspirants maintained a state of physiological relaxation, the two distinct styles of Mantra chanting—namely LC and chanting with lip movement—demonstrated a notable enhancement in attentional focus. Interestingly, this improvement in mental engagement was accompanied by a heightened activation of the sympathetic nervous system. This suggests that despite the prevailing state of calmness, the chanting styles induced a physiological state that primed the body for improved alertness and mental clarity, probably optimising cognitive performance.
Abbreviations
ECG: Electrocardiogram
HRV: Heart rate variability
HR: Heart rate
RR: Respiratory rate
LF: Low frequency
HF: High frequency
LC: Loud chanting
SC: Silent chanting
LMC: Lips movement chanting
NC: No chanting
Acknowledgments
We acknowledge the Autonomic Function Testing Laboratory of Anvesana (Research Laboratories of S-VYASA) for providing technical support during data acquisition.
We declare that there are no conflicts of interest among the authors during the conceptualisation, execution of the trial or preparation of the manuscript.
Funding: The authors disclosed receipt of the following financial support for the research, authorship and/or publication of this article: This research project was funded by S-VYASA University, Bengaluru, Karnataka.
ORCID iDs: Balaram Pradhan 
https://orcid.org/0000-0003-3248-3724
Sanjib Patra 
https://orcid.org/0000-0003-3275-0263
Authors’ Contributions
KA contributed to conceptualisation, data acquisition, analysis and interpretation and provided substantial input in explaining the underlying mechanisms of the findings.
KM was involved in subject recruitment, data acquisition and analysis.
RMA provided technical support during data acquisition and contributed to data analysis.
BP assisted in data analysis and interpretation.
SP played a significant role in conceptualisation, data acquisition, analysis and interpretation and provided critical intellectual input as the supervisor.
Data Availability Statement
Both raw and analysed data will be available from the first and corresponding authors.
Statement of Ethics
This project was approved by the Institutional Ethics Committee (IEC) of S-VYASA University.
Informed Consent
The informed consent was obtained from each participant after explaining the details about this trial.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
Both raw and analysed data will be available from the first and corresponding authors.