Introduction

         Meditation is a practice of mind-body balance or mindfulness that has been used around the world for as long as 5000 years in some cultures.  Over the last several decades, there have been multiple studies to determine the effects and benefits of meditation on physiological and psychological health.  There are different forms of meditation that can be loosely categorized into either insight meditation or concentration meditation, and each form may produce different physiological results.  Meditation is anecdotally known for its calming effect and is frequently studied to investigate the way it can influence heart rate variability.  Increased heart rate variability is an important indicator of increased parasympathetic activity and decreased sympathetic activity (Damerla, et al. 2018; Kamath. 2013; Krygier, et al, 2013; Nesvold, et al. 2011; Phongsuphap, et al. 2007).

This study used a 10-minute meditation video, intended for beginners, that featured a form of concentration meditation (7).  A separate short video on how to measure resting heart rate on the wrist was presented to the subjects as well (8).  A resting heart rate taken at the wrist is a non-invasive and easy way to collect the data and allows individuals to do it on their own.

Hypothesis

          This study tested the following hypotheses: 1) Mediation will increase heart rate variability by lowering the resting heart rate; 2) Continued use of mediation will have longer lasting effect of lowering resting heart rate by increasing parasympathetic activity. A measurable and consistent stabilization of resting heart rate in the period of post-meditation is predicted.

Materials and Methods

         11 participants (six females and five males) ranging in age from 30-62 years were chosen based on proximity to the study and willingness to participate.  All participants completed both trials and followed the proposed methodology.  Participants were provided 2 website links to videos with information needed to complete the study.  The first video link’s purpose was to familiarize the participant with the process of recording their own heart rate, a process they were asked to repeat four times per trial. Understanding of the heart rate recording process were self-reported by participants.

Once the first video demonstrating the heart rate recording process was viewed, participants were asked to provide their resting heart rate (RHR) (first recording), wait 30 minutes, and record their RHR again (second recording).  Participants were provided a 10-minute guided meditation video to watch.  At the end of the video, participants were asked to immediately provide RHR (third recording).  After 30 minutes, participants were asked to record their RHR (fourth recording).  These four data points concluded the first of two trials. Participants were asked to complete a second trial no sooner than 24 hours after the first trial, and no later than 36 hours after the first trial.  RHRs were all self-reported by participants.

Results

     There were eleven participants that completed the experiment, five men and six women (see Figure 1) ranging in age from 30 to 62 years old (see Figure 2). There were again four separate heart rates taken in each trial: 1) 30 minutes before mediation, 2) right before mediation, 3) right after mediation, and 4) 30 min after mediation.  If the participants heart rates were looked at individually comparing the heart rates immediately before and after meditation, in the first trial seven participants had lower heart rates, one participant had increased heart rate, and three participants had the same heart rat.  For the second trial if participants were looked at individually comparing the heart rates immediately before and after meditation, there were six particpants with lower heart rates, one with a higher heart rate, and four with the same heart rate.  The means for the first trial for the four separate heart rates in order were as follows: 71.91, 71.64, 67.73, and 68.73.  The means for the second trial for the four separate heart rates in order as follows: 70.91, 71.09, 68.18, 71.0.  Both trials showed that the means of the heart rate for participants were all lowest immediately following the mediation or the third heart rate taken.

Figure 3 shows for the first trial the four heart rates for all participants before and after the first trial of meditation.  Figure 4 shows the four heart rates for each participant before and after the second trial.  Figure 5 shows the first two heart rates for each participant for both trials preceding meditation. Figure 6 shows the two heart rates for each participant for both trials after meditation. Figure 7 shows the means of the heart rate for all participants for each trial for each heart rate reading. Figure 8 shows the standard deviation of the resting heart rates of all participants across both trials.

Figure 1, Participants by Sex, Figure 2, Participants by Age

Figure 3, Heart Rate by Participant, 1^st Meditation Trial, Figure 4, Heart Rate by Participant, 2^nd Meditation Trial

Figure 5, HR by Participant, Before Meditation, Figure 6, HR by Participant, After Meditation

Figure 7, Means of heart rate for each trial, Figure 8, Heart Rate Standard Deviation

Discussion

            HRV and RHR is controlled by the Autonomic Nervous System (ANS). The ANS is split into the Sympathetic Nervous System (SNS) and the Parasympathetic Nervous System (PNS). In healthy functioning individuals, the normal RTR is about 72 beats-per-minute.  Both sympathetic and parasympathetic neurons innervate the heart.  Increases in SNS activity result in a higher frequency of action potentials being released, which in turn increases heart rate (HR) and cardiac output (CO).  The PNS has the opposite effect- when activated, the PNS decreases the rate of spontaneous depolarization by releasing acetylcholine, resulting in less action potentials, decreasing the heart rate.  Meditation is thought to increase PNS activity, thereby lowering RTR.  This aligns with Damerla et al’s study; “Therefore, SNS and PNS operate antagonistically, and an increased HRV is observed under dominance of PNS activity…. Based on our study, we can conclude that mantram chanting leads to predominance of PNS in the sympatho-vagal balance. Consequently, elevated PNS activity induces smoother beat-to-beat variations of the heart, an indicator of increased HRV. The HRV curve patterns, changed from that of an erratic HR to a more regular and lower amplitude seen in states of relaxation associated with positive emotional states, validate the findings of Wolf and Abell” (Damerla et al, 2018).

The goal of this study was to determine if meditation would increase heart rate variability by lowering heart rate and if continued practice of meditation would have a longer lasting effect of lower resting heart rate by increasing parasympathetic activity.  Resting heart rate (RTR) is the rate of the heart at rest and ranges from 70-100 heartbeats per minute (Stanfield, C.L. 2017).  The results have shown that the overall mean of heart rates for both trials taken immediately after mediation, or the third heart rate collected, was the lowest over all other heart rates collected.  If each individual participant was looked at, our results of the 2^nd and 3^rd heart rate in the first trial show one participant had a higher heart rate directly after mediation, three participants had the same heart rate immediately before and after mediation, and seven participants had lower heart rates after mediation. It is unknown if there was an outside factor contributing to the higher RTR of this individual (background noise, interruption, misreading or misreporting the result, etc).  If each individual participant was looked at, our results of the 2^nd and 3^rd heart rate in the second trial show one participant had a higher heart rate directly after mediation, four participants had the same heart rate immediately before and after mediation, and six participants had lower heart rates after mediation.  One source that took heart rate data for their study determined that in the end heart rate values offered limited value in assessing the effects of mediation on the body as the mean heart observed offered no substantial changes (Nesvold, et al. 2011).  Another reference stated that different forms of mediation will have different effects on heart rate, where some forms such Chi mediation will decrease heart rate, but Kundalini yoga increases heart rate (Kamath, 2013).  “Figure 1 illustrates the findings representatively. It shows that nondirective meditation is not psychobiologically inert and it supports the idea that certain forms of meditation may induce active, rather than quiescent, cardiac dynamics.49^,50 The figure aptly depicts the subjective experience of the performer: the peaks and lows may correlate with the variations in the stream of consciousness” (Nesvold, et al. 2011).

Changes in heart rate will directly cause changes in mean arterial pressure (MAP) that are detected by arterial baroreceptors.  The arterial baroreceptors are responsible for regulating and inducing responses in both the SNS and PNS in response to changes in MAP (Stanfield, C.L. 2017).  “Based on physiological explanation of spectral components, it indicates that mediation may have the following health benefits: resetting baroreflex sensitivity, increasing parasympathetic tone, and improving efficiency of gas exchange in the lung.” (Phongsuphap, et al. 2008).

High HRV indicates that the body is able to adjust for a variety of circumstances and adjust HR and CO as required.  Low HRV is a possible indicator of susceptibility to stress and disease. This study found that meditation is reliably helpful in lowering RTR and has potential to be a useful tool in increasing the range of HRV, or in practicing HRV.  Kamanth found that the study of the effects of meditation on PNS activity could contribute to our understanding of the mind-body connection; “PNS activity is greatly enhanced during meditation compared to that before meditation.” (Kamanth, 2013).  Our study’s initial results concur with this finding.

When analyzing each participant’s data, the most significant findings were that most participants had decreased RTR immediately post meditation.  The RTR for most participants then increased in the 30min post meditation.  This indicates that the effect of the meditation on lowering RTR is temporary.  As Krygier et al found, “These techniques – such as quieting the mind and exercising self-control – can have a profound influence on mind and body, and show promise as an alternative tool to regulate emotions, mood, and stress. However, the acute and longer-term concomitants of mindfulness meditation training, and potential mechanisms of action are still not well understood” (Krygier et al, 2013).  The fact that the standard deviation was so large also indicates that comparing between participants is not as indicative of HRV range as comparing the participant’s RTR post meditation to their own data pre-meditation.  There is great variation among individuals in the study.

            Problems that the study encountered was a small study size of only 11 participants, only having two trials per participant, and relying on each participant to correctly take their heart rate.  Collecting heart rate data from participants is a non-invasive and straightforward for individuals to do, but other forms of data that could be collected such as heart rate variability, blood pressure variability, and/or baroreflex sensitivity may have had more conclusive results.  This study did not monitor or include the effects of circulating hormones (such as epinephrine, which tends to raise the heart rate), or physically prevent or rule out distractions, interruptions, or any other outside influences that could have impacted the reported data.  This study also did not include a way for participants to give feedback or additional information about their experience with the study. More trials and a larger study size would have also potentially yielded more conclusive results.

Conclusion

            The study tested the following hypotheses: 1) Mediation will increase heart rate variability by lowering the resting heart rate; 2) Continued use of mediation will have longer lasting effect of lowering resting heart rate by increasing parasympathetic activity.  Both hypotheses were supported both from the study results and the reference literature.

References

1. Damerla, V.R., Goldstein, B., Wolf, D., Madhavan, K., Patterson, N. 2018. Novice Meditators of an easily learnable audible mantram sound self-induce an increase in vagal tone during short-term practice: A preliminary study. Integrative Medicine. 17 (5). 20-28.
2. Kamath, C. 2013. Analysis of heart rate variability signal during mediation using deterministic-chaotic quantifiers. Journal of Medical Engineering & Technology. 37 (7). 436-448.
3. Krygier, J.R., Heathers, J.A.J., Shahrestani, A., Abbott, M., Gross, J.J., Kemp, A.H. 2013. Mindfulness meditation, well-being, and heart rate variability: A preliminary investigation into the impact of intensive Vipassana meditation. International Journal of Psychophysiology. 89. 305-313.
4. Nesvold, A., Fagerland, M.W., Davanger, S., Ellingsen, O., Solberg, E.E., Holen, A., Sevre, K., Atar, D. 2011. Increased heart rate variability during nondirective meditation. European Journal of Preventative Cardiology. 19 (4). 773-780.
5. Phongsuphap, S., Pongsupap, Y., Chandanamattha, P., Lursinsap, C. 2007. Changes in heart rate variability during concentration meditation. International Journal of Cardiology. 130, 481-484.
6. Stanfield, C.L. 2017. Principles of Human Physiology, sixth edition. Chapter 13-14. 391-468.
7. Meditation video: https://www.youtube.com/watch?v=U9YKY7fdwyg
8. Heart rate video: https://youtu.be/oAjnlDZH9H8