EFFECT OF TWO SELECTED YOGIC BREATHING TECHNIQUES ON HEART RATE VARIABILITY
P. Raghuraj, A. G. Ramakrishnan *, H. R. Nagendra and Shirley Telles**
Vivekananda Kendra Yoga Research Foundation, Bangalore, India.
*Department of Electrical Engineering, Indian Institute of Science,
(Received on February 9, 1998)
Abstract : The heart rate variability (HRV) is an indicator of the cardiac autonomic control. Two spectral components are usually recorded, viz. high frequency (0.15- 0.50 Hz), which is due to vagal efferent activity and a low frequency component (0.05- 0.15 Hz), due to sympathetic activity. The present study was conducted to study the HRV in two yoga practices which have been previously reported to have opposite effects, viz, sympathetic stimulation (kapalabhati, breathing at high frequency, i.e., 2.0 Hz) and reduced sympathetic activity (nadisuddhi, alternate nostril breathing). Twelve male volunteers (age range, 21 to 33 years) were assessed before and after each practice on separate days. The electrocardiogram (lead 1) was digitized on-line and off- line. analysis was done. The results showed a significant increase in low frequency (LF) power and LF/HF ratio while high frequency (HF) power was significantly lower following kapalabhati. There were no significant changes following nadisuddhi. The results suggest that kapalabhati modifies the autonomic status by increasing sympathetic activity with reduced vagal activity. The study also suggests that HRV is a more useful psychophysiological measure than heart rate alone.
Key words: Heart rate variability; high frequency breathing; alternate nostril breathing; autonomic status.
Ancient yogic texts have described a rapid breathing cleansing practice (kapalabhati) as stimulating, and slow regulated breathing, particularly through alternate nostrils (nadisuddhi pranayama) as calming (1). These descriptions have been substantiated by scientific studies. Kapalabhati was found to cause “autonomic activation”. This was observed as an immediate effect during three contiguous sessions of 5 min each, in terms of an increased heart rate and systolic blood pressure during kapalabhati (2). In contrast, nadisuddhi pranayama practised for four weeks, caused decreased heart rate, as well as systolic and diastolic blood pressure levels(3).
The heart rate is controlled by neural as well as other factors (4). Hence a decrease in heart rate may be related to an increase in vagal tone, a decrease in cardiac sympathetic activity, as well as other, non- autonomic factors. In contrast, the heart rate variability (HRV) spectrum has been established as a probe of beat-to-beat autonomic control (5). The influences of the sympathetic and parasympathetic innervation on modulation of the heart rate are quantified by the power of the heart rate variability spectrum in specific frequency bands. Hence the present study aimed at analysing the heart rate variability spectrum related to the practice of both kapalabhati and nadisuddhi pranayama to get a better understanding about the immediate effects of these practices on the autonomic status.