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| ORIGINAL ARTICLE |
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| Year : 2014 | Volume
: 2
| Issue : 1 | Page : 15-18 |
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Changes in heart rate variability following yogic visual concentration (Trataka)
BR Raghavendra, V Ramamurthy
Division of Yoga and Life Sciences, Swami Vivekananda Yoga Anusandhana Samsthana, Bengaluru, Karnataka, India
| Date of Web Publication | 3-Mar-2014 |
Correspondence Address:
B R Raghavendra
Swami Vivekananda Yoga Anusandhana Samsthana, # 19, Eknath Bhavan, Gavipuram Circle, K G Nagar, Bengaluru - 560 019, Karnataka
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/2321-449x.127975
Background: The yogic visual concentration technique, trataka is similar to meditation. Research studies have shown a shift toward the vagal tone during meditation. However, autonomic changes in trataka were not studied. Objectives: The present study was planned to assess the changes in heart rate variability (HRV) following trataka. Materials and Methods: HRV and breath rate were assessed in thirty healthy male volunteers with ages ranging from 20 to 33 years (group mean age ± SD, 23.8 ± 3.5) before and after yogic visual concentration (trataka) and control session on 2 separate days. Repeated measures analysis of variance (ANOVA) were performed with two "within subjects" factors, i.e., Factor 1: Sessions; trataka and control and Factor 2: States; "Pre", and "Post". This was followed by post-hoc analyses with Bonferroni adjustment comparing "Post" with "Pre" values. Results: There was a significant decrease in LF (RM ANOVA with Bonferroni adjustment P < 0.01) and increase in high frequency (P < 0.01) after trataka. Breath rate (P < 0.001) and heart rate (P < 0.01) were significantly reduced after trataka compared to before. Control session showed no change. Conclusions: The practice of trataka leads to increased vagal tone and reduced sympathetic arousal. Though trataka is known as cleansing technique, it could induce calm state of mind which is similar to a mental state reached by the practice of meditation. Keywords: Heart rate variability, high frequency, low frequency, trataka
How to cite this article:
Raghavendra B R, Ramamurthy V. Changes in heart rate variability following yogic visual concentration (Trataka). Heart India 2014;2:15-8 |
| Introduction | |  |
Yoga is an ancient Indian science and the way of life. Sage Patanjali (circa 900 B.C) explains the theoretical aspects yoga in 196 aphorisms called Yoga Sutras. [1] Patanjali evolved Astanga yoga (eight limbed) to reach the ultimate reality. Later around 10 th Century CE Sage Svatmarama wrote a text called Hatha Yoga Pradipika in which he explains the method of yoga techniques. He prescribes six cleansing techniques (kriyas) viz., dauti, basti, neti, trataka, nauli and kapalabhati to purify the body. The goal of Hatha Yoga is to prepare the body and mind for the practice of Raja yoga or Astanga yoga. [2]
The literal meaning of the Sanskrit word trataka is "to gaze steadily." Looking intently with an unwavering gaze at a small point until tears are shed is known as trataka (Hatha Yoga Pradipika, Ch:2, V:31). Hatha Yoga Pradipika mentions that, practice of trataka eradicates all the eye diseases, fatigue and lethargy (Hatha Yoga Pradipika, Ch:2, V:32). Though trataka is considered as cleansing technique, the final stage of trataka leads to meditative mental state. [3]
Recently, a study has been conducted to assess the immediate effect of trataka on critical flicker fusion (CFF). [4] The CFF is defined as the frequency at which a flickering stimulus is perceived to be continuous. There was a significant increase in CFF following trataka suggesting changes at the cortical level in the processes that mediate fusion.
Meditation and autonomic changes are researched extensively and shown a shift toward vagal tone during meditation. [5],[6],[7] However, there was no study evaluating autonomic changes during trataka which is similar to meditation. Hence, in the present study, we used heart rate variability (HRV) which is a well-known and extensively used method to evaluate autonomic modulation.
| Materials and Methods | | |
Participants
A total of 30 male volunteers with ages ranging from 20 to 33 years (group mean age ± SD, 23.8 ± 3.5) were recruited for this study. They were all students of a yoga university in Southern India. Their health status was evaluated by a routine clinical examination and case history. They had normal health and were not on any medication. The predetermined conditions to exclude participants from the trial were any chronic illness. Male volunteers alone were selected as autonomic and respiratory variables are known to vary with the phases of the menstrual cycle. [8] The project was approved by the institution's ethics committee. The study protocol was explained to the participants and their signed consent was obtained.
Design
Self as control design was used. Each participant was assessed in two sessions (trataka and control session) on 2 separate days. Half the subjects practiced trataka on 1 st day and control session on 2 nd day. The other half was having the order of the session reversed. Duration of both the sessions were of 25 min. Participants were assessed before and immediately after the sessions.
Assessment
Electrocardiogram (ECG) and respiration were recorded using a four channel polygraph (Biopac MP 100, USA).
HRV and heart rate
The ECG was recorded using a standard bipolar limb lead II configuration and an AC amplifier with 100 Hz high cut filter and 1.5 Hz low cut filter settings. The EKG was digitized using a 12-bit analog-to-digital converter at a sampling rate of 1024 Hz and was analyzed off-line to obtain the HRV spectrum.
Breath rate
Respiration was be recorded using a volumetric pressure transducer fixed around the trunk about 8 cm below the lower costal margin as the participants sat erect.
Intervention
Trataka (a yogic visual concentration)
Fifteen days orientation program was conducted to train participants in trataka. Theoretical aspects of trataka was explained by a senior yoga teacher on day one. The pre-recorded audio instructions for trataka was played during the session. Trataka practice consists of two distinct stages. The first stage, consisted of eye exercises, which is a preparatory practice for trataka. The eye exercise includes eyeball movements in the horizontal, vertical and diagonal direction directions and circular movements. These was performed with eyes open, in a well-lit room. This was followed by the practice of palming to relax the eyes. Palming consisted of putting slightly cupped palms over the eyes, so that the eyes perceive complete darkness. First stage lasted for 10 min. The second stage, trataka, was practiced in a dark room. Subjects were asked to fix the gaze on the flame of the candle for about 2 to 3 min, suppressing the urge to blink as far as possible. Then visualize the candle flame in between the eyebrows. This process was repeated for 2-3 rounds. Finally, subjects were asked to defocus and the practice ended with silence and then prayer. The second stage lasted for 15 min. The duration of the whole practice was 25 min.
Control session
During control session participants were asked to practice the first stage (eye exercise) for 10 min and then for next 15 min they sat quietly with closed eyes without doing any concentration or meditation.
Data extraction
HRV
Frequency domain analysis of HRV were carried out. The energy in the HRV spectrum in the following specific frequency bands were studied. The low frequency (LF) (0.04-0.15 Hz) and high frequency (HF) band (0.15-0.4 Hz). According to guidelines, LF and HF band values will be expressed as normalized units. [9]
Herat rate
The heart rate in beats per minute was calculated by counting the R waves of the QRS complex in the EKG in 60 s epochs, continuously.
Breath rate
The breath rate in cycles per minute was calculated by counting the breath cycles in 60 s epochs, continuously.
Data analysis
Statistical analysis was performed using SPSS (version 16.0). Since the same individuals were assessed in repeat sessions on separate days (i.e., trataka and control), repeated measures analysis of variance was used (ANOVA). Repeated measures ANOVA were performed with two "within subjects" factors, i.e., Factor 1: Sessions; trataka and control and Factor 2: States; "Pre" and "Post." This was followed by post-hoc analyses with Bonferroni adjustment comparing "Post" with "Pre" values.
| Results | | |
The group mean values and standard deviation for frequency domain measures of HRV, heart rate and breath rate are shown in [Table 1]. | Table 1: Changes in heart rate variability and breath rate before and after trataka and control session
Click here to view |
Repeated measures ANOVA
Repeated measures ANOVA were conducted where subjects were measured before and after trataka as well as control session.
There was a significant difference between the states for
- LF F(1, 29) = 7.58, P < 0.01;
- HF F(1, 29) = 7.60, P < 0.01;
- Hear rate F(1, 29) = 13.08, P < 0.01;
- Breath rate F(1, 29) = 20.52, P < 0.001.
There was a significant difference between the sessions for
- Heart rate F(1, 29) = 6.75, P < 0.05; and
- Breath rate F(1, 29) = 9.38, P < 0.01.
There was also a significant interaction between Session and State for
- Breath rate F (1, 29) = 14.14, P < 0.001.
Post-hoc analyses with Bonferroni adjustment
There was a significant decrease in LF (P < 0.01) and significant increase in HF (P < 0.01) after trataka. Breath rate (P < 0.001) and heart rate (P < 0.01) were significantly reduced after trataka compared to before. Control session did not show any change.
[TAG:2]Discussion[/TAG:2]
In the current study, HRV and breath rate were assessed before and after the practice of trataka and control session in thirty healthy male volunteers. There was a significant decrease in LF and increase in HF after trataka compared to before. Breath rate and heart rate were significantly reduced after trataka compared to before. Control session showed no change.
HRV refers to beat-to-beat alterations in the heart rate. In general two type of HRV analysis are used. These are frequency domain analysis and time domain analysis. In the preset study, we have used only frequency domain analysis. Earlier it was believed that the LF (LF, 0.04-0.15 Hz) band of the HRV is an index of cardiac sympathetic activity and HF (HF, 0.15-0.4 Hz) band is correlated with parasympathetic activity. [9] However this has been questioned subsequently. Recent research findings says, neither the LF band (LF) nor the HF, are considered exclusive markers of sympathetic and parasympathetic tone respectively. [10] It is found that, sympathetic activity can also regulate the HF component of HRV, though to a lesser extent than the parasympathetic influence on the LF power. The association between HF power and cardiac parasympathetic activity is stronger. Hence the HRV provides broad changes in cardiac parasympathetic regulation and changes in the LF power and LF/HF ratio have to be considered carefully. The decrease in LF power and increase in HF power after trataka suggests increased vagal modulation after trataka.
The changes in hear rate are due to several factors. The heart rate is under the control of sympathetic and parasympathetic nerves as well as humeral factors. [11] Hence, it is difficult to conclude that decrease in hear rate is only due to increased vagal tone or due to sympathetic withdrawal.
Breath rate depends upon numerous factors ranging from the level of physical activity to psychological stress. [12] In general, a decrease in breath rate is correlated with relaxation. Though trataka practice involves intense focusing, it ends with defocusing and silence. This might induce relaxation after the practice which can explain the decrease in breath rate.
The findings in the current study are similar to the earlier study on autonomic change sand two meditative states described in yoga texts, which showed reduced sympathetic arousal and increased vagal tone during dhyana. [7] Hence, it is speculated that the practice of trataka leads mental state which similar to meditation.
One of the main limitations of the study is that, assessments were not performed during the practice of trataka. Changes in HRV during trataka might have conveyed much more information. It will be interesting to have a longer duration of "Post" session (10 or 15 min) by which we can understand how much time effect of trataka sustains. In future, along with HRV other autonomic variables can be studied before during and after trataka.
In summary, considering changes in HRV, heart rate and breath rate, the present results show that, practice of trataka leads to increased vagal tone and reduced sympathetic arousal. Though trataka is known as cleansing technique, it could induce calm state of mind which is similar to a mental state reached by the practice of meditation.
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[Table 1]
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