Academic journal article International Journal of Yoga

Measures of Heart Rate Variability in Women Following a Meditation Technique

Academic journal article International Journal of Yoga

Measures of Heart Rate Variability in Women Following a Meditation Technique

Article excerpt

Byline: Hyorim. An, Ravi. Kulkarni, R. Nagarathna, H. Nagendra

Certain time domain, frequency domain and a nonlinear measure of heart rate variability are studied in women following a meditative practice called cyclic meditation. The nonlinear measure studied is the sampling entropy. We show that there is an increase in the sampling entropy in the meditative group as compared to the control group. The time domain measure called pNNx is shown to be useful in distinguishing between the meditative state and a normal resting state.


Cyclic meditation (CM) is a practice that originated in Prashanti Kuteeram, a yoga therapy center in South India. Briefly described, the practice consists of very slow movements performed with awareness of subtle shifts of balance and muscle tension during the entire exercise. People who go through the practice uniformly report a feeling of calmness and well-being at the end of the procedure. This paper describes the changes in certain measures of heart rate variability in women following the practice. The practice, performed with closed eyes, lasts about 25 min in the version used for this study. The effects of this practice on heart rate variability have previously been studied in healthy men. [sup][1] That study examined the Fourier power spectrum of the RR interval series and found a significant decrease in the low frequency (LF) component and a significant increase in the high frequency (HF) component following the practice, indicating a shift toward parasympathetic dominance.

There have been other studies on meditation and heart rate variability. Kubota et al. 0,[sup][2] studied the relationship between cardiac autonomic function and activity of the medial frontal neural circuitry. Murata et al.[3] also observed an increase in the HF power and decrease in the LF/HF ratio. It has been noted in the literature that heart rate dynamics may be different between men and women. [sup][3],[4] These studies have reported increased complexity in approximate entropy and a higher HF component in short-term electrocardiogram recordings in women compared with men. [sup][5] The aim of this study therefore was to examine certain time domain and frequency domain measures for women following the practice of CM. We also report changes in the sampling entropy (SampEn) [sup][6] discussed below as this is a non-linear measure that has been found to be useful even for short-term recordings and has been widely discussed in the literature. The changes in SampEn and the pNNx measures that are described below have not been studied before in the context of heart rate variability. These measures are described in greater detail below.

Materials and Methods

Subjects and study protocol

The subjects, 28 in number, were healthy female volunteers, resident at the center where this study was carried out. Their mean age was 25 [+ or -] 3.4 years. Each subject participated in two different sessions - one of CM lasting 23 min and another of supine rest (SR) lasting an equal number of minutes. Each session was on a different day. In the SR position, the subjects were asked to lie down and were asked to remain passive but awake with natural breathing. CM is a guided relaxation practice and the practitioner is supposed to allow the breath to flow naturally - there is definitely no attempt at controlling the breathing rate or trying to synchronize it with the body movements that are very slow. All subjects were given practice in the technique prior to the actual recording, which was performed in individual sessions with the subject following taped instructions.

The RR intervals were recorded for a period of 5 min before and after the practice of CM and the same protocol was also followed for the SR sessions. The data therefore consisted of 5-min recordings before and after each practice (CM and SR) for each subject. The RR intervals were recorded using RMS Polyrite D, a digitized polygraph manufactured by Recorders and Medicare Systems, Chandigarh, India. …

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