Abstract Chanting is a common practice in Buddhism. Nevertheless, limited studies have reported the effects of regular Buddhist chanting on physiological responses. This preliminary study aims to investigate the long-term and acute effects of regular Buddhist chanting on resting heart rate (RHR) and heart rate variability (HRV) indices that indicate parasympathetic activities (RMSSD, pNN50, HF) and general autonomic activation (SDNN, total power) and whether the effects were associated with the forms of chanting: reading aloud and reciting. Thirty young adults were divided into three groups in a non-randomized study: chanting-by-reading-aloud (Rd-Cht), chanting-by-reciting (Rct-Cht), and non-chanting control groups. Before and after the eight-week chanting practices, the HR and HRV were quantified by electrocardiography during the three testing sessions of resting, vocalizing, and recovery. The measurements were also conducted with eyes closed and eyes open conditions in each session. After the regular practice period, the Rd-Cht group had significantly lower RHR with higher RMSSD and pNN50 than pre-practice, whereas the Rct-Cht group had significantly lower recovery HR than the RHR with a higher SDNN and total power. In contrast, the control participants had significantly higher RHR with a trend of lower resting RMSSD and HF-HRV after eight weeks. The RHR and resting HRV changes in the chanting groups were independent of eye conditions. The preliminary results suggested that different forms of regular Buddhist chanting may be linked with reduced heart rate in different physiological states. Such effects could be influenced by parasympathetic modulation, which is often associated with physiological well-being.

Keywords: Religious chanting, Vagal modification, Theravada Buddhism, Mindfulness practice, Formal mind practice

Funding: This study was financially supported by the National Research Council of Thailand (R2559B086).

Citation: Wasuntarawat, C., Prathes, T., Piayo, N., and Taepavarapruk, N. 2026. Comparative effects of Buddhist chanting forms on resting heart rate and heart rate variability: A preliminary study. Natural and Life Sciences Communications. 25(3): e2026055.

Graphical Abstract:

INTRODUCTION

Buddhist chanting is a common Theravada practice in countries such as Sri Lanka, Thailand, Myanmar, Cambodia, and Laos, as well as in parts of Europe and North America, performed in temples or at home to pay homage to the Triple Gems—the Buddha, the Dhamma, and the Sangha (Sookseelueng, 2011). Chanting verses, typically in Pali with translations, includes homage, recollections, reflections, and protection verses (Amaravati-Buddhist-Monastery, 2015). Buddhist chanting is traditionally regarded as a form of mindfulness practice that involves focused attention on each word during vocalization (Inthasara, 2010; Suanmokkhaphalaram, 2017). The Buddhist canon further describes chanting as a means to transcend suffering and cultivate peace through deep comprehension and sustained mental focus (Indapanno, 2017). Chanting may be performed either by reciting from memory or by reading aloud, depending on experience. While recitation is often encouraged to enhance attention on parts of the body, such as the xiphoid process, reading can similarly foster mindfulness through attentive engagement with the text (Ponnara, 2007). Accordingly, both forms align with contemporary definitions of mindfulness as present-moment awareness (Brown et al., 2007) and attentional training (Lutz et al., 2008). Examining their effects on physiological markers, such as resting heart rate (RHR) and heart rate variability (HRV), could yield practical benefits for practitioners.

Various studies indicate that mindfulness training could foster calmness and attenuate stress reactivity, effects that are associated with reduced sympathetic adrenomedullary activity, either directly or through enhanced parasympathetic regulation (Creswell and Lindsay, 2014). Empirical findings include increased HF-HRV among Vipassana meditators (Krygier et al., 2013), reductions in respiratory rate alongside greater frontal midline theta power and elevated HF-HRV following integrative body–mind training (Tang et al., 2009), higher mean SDNN and RMSSD during yoga practice (Khattab et al., 2007), and decreased heart rate with concomitant increases in SDNN and normalized HF after acute Tai Chi exercise (Cole et al., 2016). Despite this extensive literature, chanting—particularly within the Theravada tradition—has received comparatively little scientific attention, even though it is widely practiced and regarded as a form of mental training that cultivates stillness and calm (Inthasara, 2010; Indapanno, 2017). Consequently, empirical evidence regarding the effects of regular Buddhist chanting on parasympathetic activity and whether such effects vary across chanting forms remains limited.

This preliminary study aims to examine the effects of regular chanting on cardiac autonomic function by comparing resting heart rate (Olshansky et al., 2023), parasympathetic-related HRV indices (HF, RMSSD, pNN50), and other HRV indices (LF, SDNN, total power) before and after a period of regular chanting practice. The study further explores whether chanting forms (reading aloud versus reciting) and associated eye conditions (eyes open versus eyes closed) influenced HR and HRV during resting, chanting, and recovery phases. It is hypothesized that, following eight weeks of practice, both chanting groups would exhibit higher resting parasympathetic HRV and lower RHR compared with a control group, and that the magnitude of these effects would differ between chanting forms. Specifically, chanting by reciting, typically performed with eyes closed, was expected to elicit greater autonomic effects than reading aloud due to enhanced attentional focus on the chanting content.

MATERIALS AND METHODS

Study design

The study protocol (Figure 1) was designed as a pre-post intervention assessment to investigate and compare the effects of chanting in two aspects: 1) the forms of chanting: reading-aloud (Rd-Cht) or reciting (Rct-Cht) and 2) the chanting duration: eight weeks (long term) and twenty minutes (acute) chanting on HR and HRV responses with the suggested 3Rs protocol as resting, reactivity and recovery sessions (Laborde et al., 2018). The HR and HRV responses of the chanting groups were compared with the control (Ctl) participants who did not perform any chanting or mind training in their daily lives during the eight weeks.  The study protocol was approved by the University Institutional Review Board.

Figure 1. Pre-post intervention study design for the regular chanting effect of reading-aloud (Rd-Cht) and reciting (Rct-Cht) chanting groups compared with the control group (Ctl), (n=10/group).  Before and after the eight-week practice period, the HRV investigating protocol included resting, vocalizing, and recovery sessions, each of which was composed of eyes closed (CE) and eyes open (OE) conditions. The vocalizing session was designed according to the intervention characteristics of each group.

The HRV assessments were conducted before and after the eight-week practice period for the three groups. On the investigating days, the ECG recordings were obtained during the resting, vocalizing, and recovery testing sessions (Figure 1). Due to the different eye conditions during chanting and reading, the testing protocol on the pre-practice and post-practice testing days was designed to investigate whether there was any effect of eyes closed or open on the response of the HR and HRV. All participants were asked to close (CE) and open their eyes (OE) in equal periods during resting, vocalizing, and recovery. In the twenty-minute vocalizing period, the Rct-Cht participants were requested to chant with eyes closed and eyes open for ten minutes each whereas in the Rd-Cht participants read the chanting verses aloud throughout the chanting period. The Ctl participants recited multiplication tables with eyes closed and read general books aloud for ten minutes each to simulate the eyes-closed reciting and the eyes-open reading-aloud chanting participants, respectively.

Participants

For a preliminary study, a sample size of 10-15 participants per treatment group is recommended for studies with medium or large effect size (Whitehead et al., 2016). This aligns with a sample size of 12 subjects per group as recommended by Julious (2005).  This sample size is justified by several factors, including feasibility, precision about the mean and variance, and regulatory considerations (Julious, 2005). Therefore, the study aimed for a sample of 10-12 subjects per treatment group, a range supported by both approaches.

Thirty-four undergraduate students aged 21 ± 1 years who were physically healthy and did not take any cardiovascular or psychological medications, alcohol, or nicotine were recruited and gave their written informed consents before the study. Due to the difference in workload of the practices, the participants chose to be in one of the three groups according to their interests and commitments (Ctl 11, Rd-Cht 11, Rct-Cht 12). Those who engaged in the reciting chanting group (Rct-Cht) were asked to recite the chant verses until they could chant by heart. Their chanting recall capabilities were evaluated before the pre-practice test. One of the Ctl participants could not complete the protocol due to illness, and one of the Rd-Cht participants was excluded for not joining the post-practice test session. Two participants of the Rct-Cht group were not included in the HRV analysis. One was due to high ectopic signals more than 5%, (Sarlon et al., 2022) and another one had significant outliers (> 3SD from mean) (Koerten et al., 2020). The final data were collected and analyzed from thirty participants (Ctl 10, Rd-Cht 10, and Rct-Cht 10), with the female-to-male ratio of 8:2, 7:3, and 9:1, respectively.

Chanting practice settings

The chanting participants were given the Pali-Thai chanting books for their daily chanting practice for eight weeks. The chanting verses included the Opening Homage, the Preliminary Homage, the Going to the Three Refuges, the Homage to the Triple Gems, the Bahum, the Maha Jayamangala Gatha, the repeated chanting of the Homage to the Buddha for one plus years-age times following a well-known instruction of Venerable monk Charan Thitadhammo (Ponnara, 2007) and followed by the Reflection on Universal Well-being, the Requesting Universal Forgiveness, the Transference of Merit, the Sharing of Blessing and the Closing Homage. The participants chanted the Pali with Thai translation out loud for 45-60 minutes depending on their reading or reciting speed.

During chanting, the Rd-Cht participants were reading chanting books aloud whereas in the Rct-Cht participants were reciting all the chanting verses with eyes closed and tried to focus their attention on one point at the tip of the xiphoid process (Ponnara, 2007) or at the moving mouth and jaw. For the daily chanting places, though few participants preferred to chant in their rooms, most participants chanted in the chanting room of the Faculty of Medical Science on working days and in their residential rooms during weekends. If they missed the daily chanting, they could make up for the following day otherwise they would be excluded.

Signal acquisition

All participants were accustomed to the ECG lead II setting and laboratory environment before joining the HRV pre-practice test sessions. The condition in the laboratory was well-monitored and maintained at a steady temperature (25°C) and quiet environment. They were requested to prepare themselves before the pre-practice and post-practice testing days including refraining from alcohol and strenuous exercise for forty-eight hours, caffeine and energy drinks for twenty-four hours, and consuming last meal more than two hours before visiting the laboratory. All participants confirmed their self-preparation following the instructions for the pre-practice and post-practice testing days.

The HRV measurement was conducted via ECG lead II at a 1 kHz sampling rate (Task-Force, 1996) using the PowerLab system (ADI instrument, Sydney, Australia). Once the ECG signal recording system was set up, the participants rested in a sitting posture, hands on thighs for five minutes before starting the experimental sessions. During the resting session, they were asked to stay seated, relax, and breathe spontaneously without speaking with their eyes closed and eyes open for three minutes respectively. The vocalizing session for the Rct-Cht and Ctl groups was divided into the eyes-closed condition (ten minutes) and the eyes-open condition (ten minutes). The Ctl participants recited multiplication tables with eyes closed and read general books aloud for ten minutes each to simulate the eyes-closed reciting and the eyes-open reading-aloud chanting participants, respectively. Participants in the Rd-Cht group had their eyes open throughout the vocalizing session. During the recovery session, the recovery signals were recorded for all participants with their eyes closed and eyes open for three minutes, respectively.

HRV assessment

Before conducting HRV analysis, the ECG recording was visually scanned for different morphologies of QRS wave, ectopic, and artifact as well as automatically examined by the software to remove any ectopic beats. The technical artifacts in this study were unlikely to occur since the participants were young and cooperative, with minimal motion and well-fastened electrodes during the measurements.  The normal RR intervals were analyzed for the time domain and the frequency domain at six epochs with the Lab Chart 7 Pro software V.7.3.7. Four epochs lasted three minutes with CE and OE during the resting and recovery sessions. Two epochs were from five minutes near the end of the first and the second half of the vocalizing period, respectively. The five-minute segments near the end of CE and OE were chosen to allow sufficient time for incubating the effect of chanting and were advised for short-term HRV measurement (Task-Force, 1996; Nunan et al., 2010).

In time-domain analysis, the R-R interval series of each epoch were quantified for 1) mean HR: mean heart rate (beats/min), 2) SDNN: standard deviation of NN intervals (ms), 3) RMSSD: root-mean-square of the differences between adjacent NN intervals (ms), and 4) pNN50: percent on difference between adjacent NN intervals which are greater than 50 ms (%). For the frequency domain, the parameters of HRV spectrum analysis were 1) total power of the spectrum (ms²), 2) HF:  high-frequency band, which is between 0.15-0.4 Hz (ms²), 3) LF: low-frequency band between 0.04–0.15 Hz (ms²), and 4) LF/HF ratio.

Statistical analysis

The data are presented as mean ± SD. The statistical analyses were conducted using IBM SPSS Statistics software version 27 (SPSS Inc., Chicago, IL, USA) with a statistical significance level of P < 0.05. The homogeneity of variance was tested using Levene’s test. Repeated measurement ANOVA (3 groups x 2 trials x 3 sessions x 2 eye conditions) was used for the comparison of the mean between groups at different time points and eye conditions. The one-way ANOVA was used for a comparison of the changes in resting HR and HRV indices after the regular practice period among three groups. Post hoc pairwise comparisons with LSD or Dunnett’s T3 were used, where the equal variances were assumed or were not assumed, respectively.  Mean comparison between the pre- and post-practices, the eyes closed, and open conditions was tested with a paired t-test, and the sphericity of data was tested with Mauchly’s test. If sphericity was not assumed, it was corrected with the Greenhouse-Geisser correction. The effect size for a paired-sample t-test was reported and classified according to Cohen’s d as small (d = 0.2), medium (d = 0.5) and large (d ≥ 0.8).

RESULTS

Effects of eyes closed and eyes open on heart rate

A repeated-measures ANOVA (2 eye conditions × 3 sessions × 2 trials × 3 groups) showed no overall group differences in heart rate (HR) across eyes-closed and eyes-open conditions during the three testing sessions before and after the regular practice period (P = 0.952). Comparisons between eye conditions indicated significant differences only in the recovery session, with higher HR in the eyes-open than eyes-closed condition in the Rct-Cht group during the pre-practice trial (P = 0.022) (Figure 2c)   and in the control group both before (P = 0.023) and after eight weeks (P = 0.008) (Figure 2a).

Analysis of the acute effects of vocalizing revealed that, at pre-practice, HR during vocalization was significantly higher than resting HR in both eye conditions across all groups (all P < 0.05). At post-practice, this effect remained evident only in the two chanting groups (Rd-Cht and Rct-Cht: P < 0.01) (Figure 2b and 2c), whereas in the control group, a significant increase in HR during vocalization was observed only under the eyes-closed condition (P = 0.047) (Figure 2a). Following the 20-minute vocalization period, recovery HR in the eyes-closed condition among chanting participants decreased and returned to resting levels at both pre- and post-practice assessments. Notably, only the Rct-Cht group exhibited a post-practice recovery eyes-closed HR that was significantly lower than its resting eyes-closed HR (P = 0.021) (Figure 2c). In contrast, recovery HR in the eyes-open condition for both chanting groups remained comparable to resting levels before and after the eight-week practice period (Figure 2b and 2c), whereas the control group showed elevated recovery eyes-open HR at pre-practice (P = 0.040) that normalized after eight weeks (Figure 2a).

Overall, following eight weeks of daily chanting practice, the Rd-Cht group exhibited a tendency toward lower heart rate (HR) at post-practice compared with pre-practice during both resting and chanting sessions (Figure 2b), whereas the Rct-Cht group showed a similar trend only during chanting (Figure 2c). For both chanting forms, HR tended to decrease during the recovery session under eyes-closed conditions. In contrast, the control group demonstrated higher HR across all three experimental sessions at post-practice (Figure 2a).

At rest, the Rd-Cht group showed a trend toward reduced HR in both eyes-closed (P = 0.090) and eyes-open (P = 0.081) conditions (Figure 2b), while no changes in resting HR were observed in the Rct-Cht group in either eye condition after eight weeks (Figure 2c). Conversely, the control group exhibited a significant increase in resting HR under eyes-open conditions (P = 0.013) and a marginal increase under eyes-closed conditions (P = 0.087) (Figure 2a).

Figure 2.  Heart rate responses during resting, vocalizing, and recovery sessions for (a) control, (b) reading-chanting, and (c) reciting-chanting groups, under both closed-eyes (CE) and open-eyes (OE) conditions. Data (n = 10 per group) are presented as means. Significance is indicated as follows:  *P < 0.05 and **P < 0.01 vs. eyes-closed (CE) within the same session and week; #P < 0.05 and ##P < 0.01 vs. resting within the same eye condition; and @P < 0.05 vs. pre-practice within the same session. Error bars are omitted to improve visual clarity. Statistical comparisons of HR across weeks, groups, and sessions were conducted using paired t-tests and are presented in Tables 2 and 3 of the Supplementary Data.

Effects of regular chanting practice on HR and HRV indices

Because each group experienced both eyes-closed and eyes-open conditions across the three testing sessions—with the exception of the Rd-Cht group’s vocalization session, which was conducted exclusively with eyes open—eye-condition exposure was largely comparable across groups. Only 17% (3 of 18) of all sessions (3 sessions × 2 trials × 3 groups) showed significant heart rate differences between eyes-closed and eyes-open conditions (indicated by * and ** in Figures 2a and 2c). Accordingly, subsequent analyses incorporated data from both eye conditions across all experimental sessions to examine the main effects of daily chanting practice on heart rate and HRV indices (Table 1).

Heart rate

A repeated-measures ANOVA (3 sessions × 2 trials × 3 groups) revealed significant effects on heart rate across sessions, trials, and groups (P = 0.022). After eight weeks, the Rd-Cht group demonstrated a significant reduction in resting HR (P = 0.013), whereas no such change was observed in the Rct-Cht group. In contrast, the control group exhibited a significant increase in resting HR over the same period (P = 0.002; Table 1). HR during vocalization was significantly higher than resting heart rate in all three groups at both pre-practice (all P < 0.001) and post-practice assessments (Rd-Cht and Rct-Cht: P < 0.001; control: P = 0.013; Table 1). Notably, only the Rct-Cht group showed a recovery HR that was significantly lower than resting HR (P = 0.045).

Parasympathetic HRV indices 

A repeated-measures ANOVA (3 sessions × 2 trials × 3 groups) revealed significant differences in RMSSD (P = 0.008), but not in pNN50 (P = 0.266) or HF (P = 0.126), across sessions, trials, and groups. Following eight weeks of practice, the Rd-Cht group demonstrated significant increases in resting RMSSD (P = 0.045), resting pNN50 (P = 0.022), and chanting RMSSD (P = 0.028), along with a trend toward higher resting HF (P = 0.079) compared with pre-practice levels. In contrast, no significant changes in resting RMSSD, pNN50, or HF were observed in the Rct-Cht group (Table 1). Conversely, the control group showed a tendency toward reduced resting RMSSD and HF (P = 0.083), with no change in resting pNN50 after eight weeks.

Relative to resting conditions, the Rd-Cht group exhibited significantly lower RMSSD (P < 0.001) and pNN50 (P = 0.015) during vocalization at pre-practice, and significantly lower pNN50 (P = 0.001) and HF (P = 0.023), with a trend toward reduced RMSSD (P = 0.058), at post-practice (Table 1). The Rct-Cht group similarly showed significant reductions in vocalizing RMSSD and pNN50 both before (RMSSD: P = 0.037; pNN50: P = 0.044) and after the eight-week practice period (RMSSD: P = 0.017; pNN50: P = 0.014). In contrast, the control group demonstrated a significant reduction only in vocalizing pNN50 at post-practice (P = 0.043), with no differences in vocalizing RMSSD or HF relative to resting levels at either pre- or post-practice. During recovery in both trials, RMSSD, pNN50, and HF in all three groups returned to resting values (Table 1).

Table 1. The heart rate (HR) and HRV indices during resting, vocalizing, and recovery sessions before and after eight weeks of daily chanting practice, compared to the control group who did not perform any chanting. The analyzed data included eye-closed and eye-open HR in each experimental session and were expressed as mean ± SD.

Note: *P < 0.05, ** P < 0.01 vs pre-practice of the same experimental sessions and group. # P < 0.05, ## P < 0.01, ### P < 0.001 vs resting session of the same week and group. Statistical comparisons of HR and HRV parameters across weeks, groups, and sessions were conducted using paired t-tests and are presented in Tables 4 and 5 of the Supplementary Data.

Baroreflex-related HRV index

A repeated-measures ANOVA (3 sessions × 2 trials × 3 groups) showed no significant differences in LF power among sessions, trials, or groups (P = 0.103). LF power at rest, during vocalizing, and during recovery did not change significantly from week 0 to week 8 in any group (Table 1). During vocalizing, LF power was significantly higher than at rest in the control group at both weeks (P = 0.001, P = 0.007) and in the Rd-Cht group at week 8 (P = 0.026). During recovery, LF power was significantly elevated compared with rest in the control group at both weeks (P = 0.004, P = 0.007) and in the Rd-Cht group at week 0 (P = 0.007). No significant differences in LF power between vocalizing or recovery and rest were observed in the Rct-Cht group at either time point.

Spectral ratio (LF/HF)

Similarly, no significant pre- to post-practice changes in resting, vocalizing, or recovery LF/HF were observed in either chanting group. Within the Rd-Cht group, vocalizing LF/HF was significantly elevated relative to resting at both weeks (P = 0.012, P < 0.001), and recovery LF/HF was significantly higher than resting at pre-practice (P = 0.005). Furthermore, post-practice recovery LF/HF exceeded post-practice resting LF/HF in both the Rd-Cht (P = 0.002) and Rct-Cht (P = 0.029) groups. By contrast, the control group exhibited a significant decrease in recovery LF/HF after eight weeks (P = 0.027), while resting and vocalizing LF/HF remained unchanged (Table 1). Vocalizing and recovery LF/HF in the control group were significantly higher than resting at week 0 (P = 0.019, P = 0.002), but this difference was not observed after eight weeks.

Overall autonomic HRV indices

A repeated-measures ANOVA (3 sessions × 2 trials × 3 groups) revealed no significant differences for SDNN or total power across sessions, trials, or groups (SDNN: P = 0.626; total power: P = 0.601). Following eight weeks of chanting practice, the Rct-Cht group exhibited a nonsignificant trend toward reduced resting SDNN (P = 0.094). No changes in SDNN were observed in the control group across sessions; however, their total power showed a decreasing trend after eight weeks.

Relative to resting SDNN, the Rct-Cht group exhibited a significant reduction in SDNN during chanting at week 0 (P = 0.047); this difference was not maintained after the intervention. In contrast, the Rd-Cht group showed significantly higher recovery SDNN compared with resting values both before (P = 0.003) and after (P = 0.048) practice, with recovery total power also significantly elevated at week 0 only (P = 0.006). For the Rct-Cht group, recovery SDNN and total power were significantly increased relative to rest only following the eight-week practice period (SDNN: P = 0.008; total power: P = 0.033). In the control group, recovery SDNN was significantly higher than resting SDNN at baseline (P = 0.042) but not post-intervention, whereas recovery total power showed a significant increase only after eight weeks (P = 0.014; Table 1).

Changes in resting HR and HRV indices

Changes in resting HR and HRV indices across resting, vocalizing, and recovery sessions over the eight-week intervention were examined using a repeated-measures ANOVA (3 sessions × 3 groups). A significant session-by-group effect was observed (P = 0.001). Post hoc analyses indicated that group differences were present only during the resting session; no significant differences were detected during the vocalizing or recovery sessions. Accordingly, intervention-related changes are reported only for the resting condition (Figure 3).

Changes in resting HR and HRV indices following eight weeks of Rd-Cht practice were directionally opposite to those observed in the control group. One-way ANOVA with post hoc pairwise comparisons using the LSD procedure indicated that reductions in resting HR in the Rd-Cht group were significantly greater than those in both the control group (P < 0.001) and the Rct-Cht group (P = 0.049). Moreover, increases in RMSSD, pNN50, and HF in the Rd-Cht group were significantly larger than those in the control group (P = 0.014, 0.017, and 0.008, respectively). After eight weeks of practice, the Rct-Cht group showed directional changes in vagal-indicating HRV indices similar to those observed in the Rd-Cht group, but exhibited a significantly greater increase in resting HF compared with the control group (P = 0.039). Changes in SDNN, LF, and LF/HF were non-significantly lower, whereas changes in RMSSD, pNN50, and total power were non-significantly greater than those of the control group (Figure 3).

Figure 3. Changes in the resting heart rate and resting HRV indices after the eight-week practice, either by reading aloud or reciting forms of chanting, compared to the controls who did not practice chanting. Data were expressed as mean ± SD, * P < 0.05, ** P < 0.01, *** P < 0.001. Statistical comparisons of changes in HR and HRV parameters across groups were conducted using one-way ANOVA and are presented in Table 6 of the Supplementary Data.

DISCUSSION

This preliminary study compares the effects of different forms of regular Buddhist chanting in the Theravada tradition on resting HR and HRV. Chanting with either eyes closed (CE) or eyes open (OE) did not affect resting or vocalizing HR or HRV indices across trials in any of the three experimental groups (Figure 2). The acute and long-term effects of reading-aloud and recitation chanting practices on HR and HRV indices, along with their practical implications, are discussed in the following sections.

Acute effects of chanting

All groups exhibited significantly increased HR during vocalization compared to resting (Figure 2, Table 1). Interestingly, only the two chanting groups showed significantly decreased RMSSD and pNN50 during vocalization, with the Rd-Cht group also showing decreased HF after the eight-week practice (Table 1). These findings align with a previous study (Gao et al., 2019), which reported decreased HF, VLF, and total power during repetitive mental chanting, independent of implicit language processing and respiratory activity. This suggests that elevated HR during chanting stems from vagal withdrawal, whereas increased HR in the control group may involve increased sympathetic activity during general vocalization (Dodo and Hashimoto, 2019).

The acute vagal HRV reductions observed here contrast with trends in other contemplative practices. For instance, Muslim prayer (salat), yoga mantras and rosary prayer, and nondirective meditation have been associated with increased HF power and baroreflex sensitivity (Bernardi et al., 2001; Nesvold et al., 2012; Doufesh et al., 2014). These discrepancies likely arise because Buddhist chanting is not a rhythmic repetition designed to stabilize breathing at 6 breaths/min (Bernardi et al., 2001). Instead, it involves narrated worship and doctrinal content without a fixed respiratory rate. Typical speaking or reading can increase respiration to 14–31 breaths/min compared to quiet breathing (7-19 breaths/min) (Hoit and Lohmeier, 2000). Importantly, this parasympathetic withdrawal during chanting may reflect heightened mindful attention and self-awareness, as lower HF-HRV is associated with vigilant states and intentional focus (Watford et al., 2020). One possible explanation is that Theravada chanting, unlike other chanting practices, emphasizes sustained attention to sacred texts and their meanings, potentially facilitating altered states of consciousness linked to spiritual growth, healing, and devotion. 

Long-term effects of chanting

During resting

The preliminary findings revealed a significant association between daily reading-aloud practice and a reduction in RHR. This was substantiated by a significant increase in the parasympathetic activity indices RMSSD and pNN50 (Table 1). Conversely, daily recitation practice did not exhibit a similar association. In contrast, non-chanting participants showed significantly higher resting HR after eight weeks, along with a trend toward opposing changes in HRV indices (Figure 3). When changes in resting HR and HRV indices from pre- to post-intervention were compared with the control group, the Rd-Cht group demonstrated significantly lower resting HR and higher RMSSD, pNN50, and HF power. In contrast, the Rct-Cht group showed only a trend toward lower RHR and a significantly higher HF component compared with controls (Figure 3).

The reduction in RHR is clinically meaningful, as RHR is a fundamental indicator of cardiovascular and overall health (Olshansky et al., 2023) and is associated with autonomic function (van Dijk et al., 1991). Elevated RHR has been linked to increased risk of cardiovascular disease, cancer, all-cause mortality (Hsia et al., 2009; Cooney et al., 2010; Jensen et al., 2013; Aune et al., 2017), and psychiatric conditions such as anxiety and depression (Ventriglio et al., 2015), suggesting that the observed lowering of heart rate via enhanced parasympathetic activity and/or reduced sympathetic drive is beneficial.

In addition, the increase in resting vagal tone following chanting practice may support attentional regulation. After eight weeks, chanting participants exhibited higher resting RMSSD and pNN50 relative to baseline, whereas these indices declined in the control group (Table 1). It was suggested that high resting state HRV may be correlated with attention maintenance (Siennicka et al., 2019) and the vagal firing by the influence of the neocortex was increased during sustained attention (Richards and Casey, 1991). This autonomic profile parallels effects reported for other long-term mind–body practices, including mindfulness meditation (Solberg et al., 2004), mindfulness-based stress reduction (Pascoe et al., 2017; Wang et al., 2022), and Tai Chi or yoga (Zou et al., 2018), indicating improved autonomic and stress regulation. Eight weeks of chanting did not alter the resting baroreflex-related autonomic index, as LF did not change from pre- to post-practice levels at rest in any group (Table 1), suggesting preserved tonic autonomic control (Goldstein et al., 2011).

During recovery

Vocalizing acted as an interference to the resting state across all groups, initially increasing HR before parasympathetic activation facilitated a return to baseline (Porges, 2007). While all participants recovered to resting levels both before and after the eight-week intervention, only the Rct-Cht group achieved a recovery HR significantly lower than their initial baseline following the twenty-minute chanting session (Table 1). This enhanced recovery was particularly evident during the eyes-closed condition (Figure 2c) and was accompanied by significant increases in recovery SDNN and total power, suggesting improved autonomic regulation unique to the Rct-Cht practice (Table 1).

Evidence from neuroimaging (Weng et al., 2020) and electrophysiological (Wöstmann et al., 2020) studies suggests that eyes-closed conditions promote greater attentional engagement and sensory focus than eyes-open states. Given the longer eyes-closed duration during reciting chanting, this practice may facilitate sustained attention during and after chanting. Consistent with prior findings linking sustained attention to higher resting HRV (Siennicka et al., 2019) and increased vagal activity (Richards and Casey, 1991), the robust recovery in SDNN and total power observed in the Rct-Cht group, along with an increase in vagal HRV indices (RMSSD, pNN50, HF) back to resting values, may reflect attentional maintenance following chanting.

Higher SDNN and total power are generally indicative of healthier autonomic regulation (Kim et al., 2018; Hernández-Vicente et al., 2020) and are closely correlated indices (Task-Force, 1996). SDNN is an overall index of HRV that reflects all cyclic components contributing to variability, whereas total power represents the variance of all NN intervals and is calculated as the sum of very low-frequency (VLF), low-frequency (LF), and high-frequency (HF) components of the HRV signal. In short-term recordings (2–5 min), SDNN primarily reflects parasympathetic influences (Shaffer et al., 2014), whereas total power reflects overall variability, with HF linked to parasympathetic activity and LF to baroreflex modulation (McCraty and Shaffer, 2015). The VLF could be avoided from the power interpretation while in a short-term recording (Task-Force, 1996) due to its reflection on the renin-angiotensin system and thermoregulatory mechanism (Hadase et al., 2004). In this study, recovery RMSSD, pNN50, and HF in the Rct-Cht group did not exceed resting levels, suggesting that the observed increases in recovery SDNN and total power were not driven solely by parasympathetic activation but may also involve other mechanisms, such as enhanced baroreceptor activity.

Elevated LF during vocalization and recovery in the control group likely reflected acute vocalization-related responses. In contrast, the Rd-Cht group showed practice-related modulation, with sustained vocalizing LF and reduced recovery LF after training, suggesting more efficient post-vocalization autonomic re-stabilization. An interesting finding was that recovery LF/HF decreased after eight weeks in the control group but not in the chanting groups. Given the limitations of LF/HF as a marker of sympathovagal balance (Billman, 2013; Shaffer and Ginsberg, 2017), this pattern should not be interpreted as a direct change in sympathetic dominance. Instead, reductions in recovery LF/HF likely reflect attenuation of low-frequency, baroreflex-related oscillations, whereas the persistence of LF/HF in the chanting groups may indicate sustained rhythmic autonomic modulation. Overall, these findings suggest that different interventions may influence the dynamics of autonomic recovery rather than baseline autonomic tone.

Practical implications of the forms of chanting: Reading aloud and reciting

Reading can enhance attention (Commodari and Guarnera, 2005). Chanting by reading aloud may increase attention while reading the unfamiliar Pali chanting verses and grasping their meanings from the translations which may center the mental activity on the present task and may enhance mindfulness - the awareness of moment-to-moment experience with acceptance and nonjudgment (Keng et al., 2011). The preliminary results of this study showed that reading-aloud chanting practice could be linked with lowering resting HR that is supported by the increase in the vagal indicating-HRV indices that lead to mind calmness and stress reduction. It has been suggested that low resting vagal tone may be a valid and reliable biological correlation to anxiety in youth (Scott and Weems, 2014) and to the psychopathology that occurs in adolescents who are exposed to high stress (McLaughlin et al., 2015). It has also been suggested that the vagal function may offer a mediator of the pathway to well-being (Wilkie et al., 2022).

Chanting by reciting the verses by heart with eyes closed may also be an opportunity to enhance mindfulness. While closing the eyes, the brain activity was more active and in unstable dynamic patterns which suggested that the brain may engage in sensation focusing and attention (Weng et al., 2020; Wöstmann et al., 2020). However, while closing the eyes and reciting the chanting verses, the practitioner should focus the mind and be in the present moment of chanting. Otherwise, the mind can get trapped in thought and memory, wandering to the past or future, not being in the present moment which is the key essence of being mindful (Keng et al., 2011). Although there was no evidence of reduced RHR after regular practice like in the Rd-Cht group, the HR was significantly decreased during the recovery state, immediately after reciting chanting (Figure 2c, Table 1). These findings, along with the strong recovery in SDNN and total power and an increase in vagal HRV indices, could be linked with sensation focusing and attention.

Based on these preliminary findings, the following evidence-informed practice recommendations may be drawn. Reading-aloud chanting may be recommended as a structured contemplative practice for stress reduction and autonomic regulation. Such chanting form may facilitate mindfulness and enhance vagal tone, as reflected by reduced resting HR and increased vagal HRV indices. In addition, novice chanters, who cannot memorize the chanting verses like more experienced chanters, can gain beneficial effect by reading the chanting verses aloud and using the words as an anchor of mindful practicing while chanting. Reciting chanting with eyes closed may be recommended as an adjunct practice to support attentional engagement and sensory focus, especially during and immediately after chanting. However, anchoring attention to vocalization, breath, or bodily sensations should accompany recitation to minimize mind wandering.

Limitations and future research

One of the limitations of this study was a lack of randomization due to the highly demanding daily practice of the chanting experimental groups. Thus, the participants were asked to self-select into the chanting or control groups based on their commitment capacity. This may have contributed to systematic baseline differences, such as motivation, discipline and training period, that could influence outcomes, thereby constraining internal validity and limiting the strength of causal conclusions. In addition, there was no active control group, i.e., the control group was not offered any activity so the placebo effect could not be assessed. Several factors outside the scope of this study, such as emotional stress and physical activities of daily living, may have affected cardiac chronotropy. Incorporating stress evaluations and physical activity records in future studies would provide a more comprehensive analysis. Additional experiments incorporating randomization, a larger sample size, an active control, and improved control of confounding factors may strengthen the results of this study.

Interpretation of these findings must account for sexual dimorphism in cardiac autonomic regulation. Females generally exhibit higher resting heart rates and lower HRV than males (Umetani et al., 1998; Koenig and Thayer, 2016). Although this study was not designed for sex-specific analysis, the high proportion of female participants across all groups may have influenced absolute HR and HRV levels, potentially limiting generalizability to male populations. Future research should utilize balanced or stratified samples to further clarify these sex-specific mechanisms.

Investigating breathing pace during rest and recovery after Buddhist chanting may reveal enhanced parasympathetic activity mediated by respiratory sinus arrhythmia. Furthermore, measuring sympathetic activity could provide insight into autonomic balance during and after chanting. While our results suggest that different chanting forms differentially influence parasympathetic HRV indices, these practices may also affect baroreflex pathways (Krygier et al., 2013; Mir et al., 2024) or local vasoactive substances (Lu and Kuo, 2013; Kemper et al., 2015)—mechanisms previously observed in Tai Chi and meditation. Future research should therefore incorporate resting blood pressure or plasma vasoactive substance measurements to further elucidate these underlying mechanisms.

Future studies should examine the effects of chanting in sub-healthy populations, such as older adults (Mungkhunthod et al., 2025) or hypertensive patients (Songthai et al., 2014; Anjana et al., 2022). Comparative studies of experienced and novice chanters may further clarify whether HRV outcomes depend on attentional proficiency and practice experience rather than chanting form alone.

CONCLUSION

Buddhist chanting can be a technique to practice mindfulness. However, few studies have examined the physiological impact of regular Buddhist chanting. The present preliminary study investigates the associations of regular chanting and chanting forms on resting HR and HRV. These findings provide initial evidence that various forms of regular Buddhist chanting are associated with reduced heart rates across different physiological states. Specifically, HRV indices suggest that the decreased resting heart rate in the reading-aloud group is mediated by parasympathetic activity—a key indicator of physiological well-being—whereas the reciting-by-heart group exhibits enhanced autonomic regulation during recovery. These results encourage chanting practice by demonstrating that both novices and experienced chanters benefit; specifically, reading-aloud may promote stress reduction while reciting-by-heart may enhance autonomic regulation associated with attentional engagement.

ACKNOWLEDGEMENTS

The authors are immensely grateful to Dr. Wattana Watanapa, Faculty of Medicine Siriraj Hospital, Mahidol University, for the inspired ANS & HRV investigation and the initial support of the HRV lab setting. Also, they appreciate valuable input from Dr. Wisa Supanpaiboon and Dr. Phanchana Sanguansermsri, Faculty of Medical Science, Naresuan University, for the comments on manuscript preparation. This article is dedicated to the memory of Dr. Niwat Taepavarapruk, the late, talented, and respected physiologist. 

AUTHOR CONTRIBUTIONS

Chanchira Wasuntarawat: Conceptualization (Equal), Methodology (Equal), Validation (Lead), Resources (Equal), Investigation (Equal), Formal Analysis (Lead), Data Curation (Lead), Writing – Original Draft (Lead), Writing – Review & Editing (Lead), Visualization (Lead), Project Administration (Equal), Funding Acquisition (Equal); Titima Prathes: Resources (Equal), Investigation (Equal); Narongsak Piayo: Resources (Supporting), Funding Acquisition (Supporting); Niwat Taepavarapruk: Conceptualization (Equal), Methodology (Equal), Investigation (Supporting), Project Administration (Equal), Funding Acquisition (Equal). All authors had made considerable contributions to the work and approved it for publication.

ETHICS APPROVAL

 All procedures performed in studies involving human participants were approved by the Naresuan University Institutional Review Board (NU-IRB) (Approval No: R2559B086), with certification granted on November 26, 2014.

CONFLICT OF INTEREST

The authors declare that they hold no competing interests.

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Supplementary Data

Table 2.  Statistical comparisons of heart rate between eyes-closed (CE) and eyes-open (OE) conditions at baseline (Week 0) and post-intervention (Week 8) across experimental groups and sessions. Values represent paired t-test statistics (t), P-values, and effect sizes (Cohen’s d). Only statistically significant results are presented.

Table 3. Statistical comparisons of session effects (within week and eye condition), comparing resting with vocalizing or recovery across the control, reading, and reciting groups at baseline (Week 0) and post-intervention (Week 8). Paired t-test results are reported as t-statistics, P-values, and effect sizes (Cohen’s d). Only statistically significant results are presented.

Table 4. Statistical comparisons of time effects between baseline (Week 0) and post-intervention (Week 8) for HR and HRV parameters across experimental groups and sessions. Paired t-test results are reported as t-statistics, P-values, and effect sizes (Cohen’s d) for HR and HRV parameters during resting, vocalizing, and recovery conditions. Only statistically significant results are presented.

Table 5. Statistical comparisons of within-week and condition effects between resting and vocalizing or recovery in the control, reading, and reciting groups at baseline (Week 0) and post-intervention (Week 8). Paired t-test results are reported as t-statistics, P-values, and effect sizes (Cohen’s d) for HR and HRV parameters. Only statistically significant results are presented.

Table 6. Results of one-way ANOVA comparing changes in HR and HRV parameters among the control, reading, and reciting groups. The table reports F-statistics, P-values, and effect sizes (η²), along with significant pairwise differences identified using Fisher’s least significant difference (LSD) post hoc tests. Only statistically significant results are presented.