DISCUSSION

In the present study, we have recorded time course of the effect of yoga training on BP and HR in essential hypertensive patients. The marginal and insignificant increase in BP at the end of the first week is likely to be due to adjustment of the subjects to the study environment. From second week onwards there was a significant and progressive decrease in HR and RPP and from 3rd week onwards in SP, DP and MP as well. Our results are in agreement with the findings of Patel and North (16) who have reported that six weeks treatment with yoga relaxation produces a significant reduction in BP. Sunder et al (7) also have demonstrated that shavasan therapy results in statistically significant fall in both mean systolic and diastolic pressures as well as requirement of anti-hypertensive drugs. Shavasan is known to produce psychosomatic relaxation. In an earlier work from our laboratories, we have demonstrated that shavasan produces a consistent and significant reduction in oxygen consumption and this is associated with a feeling of psychosomatic relaxation (20). Stress reduction with behavioral procedures like yoga is known to benefit hypertensive patients by lowering their BP (13). Bera et al (21) also have reported that the effects of stress are reversed in significantly shorter time in shavasan. Blackwell et al (10) have also demonstrated that transcendental meditation reduces anxiety level and blood pressure. Malathi and Damodaran have demonstrated the beneficial role of yoga in not only causing reduction in basal anxiety level but also attenuating the increase in anxiety score in stressful states like examination (2). The early and significant reduction in BP and HR in our subjects might be due to our training schedule consisting of shavasan as well as relaxing postures ( asans) and breathing exercises ( pranayams). A significant reduction in RPP indicates a decrease in myocardial oxygen consumption and load on heart (17). This can be explained on the basis of decrease in sympathetic drive to the heart. Our findings are consistent with those of Selvamurthy et al (5) who have reported that yogic training produces a significant decrease in BP associated with improvement of baroreflex sensitivity and attenuation of sympathetic and reninangiotensin activity. 

IHG test provides pressure stimuli to cardiovascular system through efferent sympathetic pathways with a resultant increase in HR and BP (19). BP response to IHG in our study is in agreement with the observation of other workers who have reported a rise in BP with IHG in essential hypertensive patients (22, 23). A blunted BP response to IHG may be due to insufficient sympathetic response in our hypertensive patients. Normally, IHG test increases DP by 16 mm Hg or more and a rise of 10 mm Hg or less indicates abnormal cardiovascular reflex regulation (24). In our subjects, IHG test increased the mean DP by 8 mm Hg and HR by 6 beats/min before yoga training. Both these changes were insufficient and statistically insignificant. After yoga training, HR as well as DP increased significantly in response to IHG test. Here, it is interesting to note that Selvamurthy et al have concluded that yoga training results in an improvement of baroreflex sensitivity (5). Our results are different from earlier studies reporting that sympathetic reactivity is reduced following yoga training (25) and the pressure response to emotional and physical stimuli becomes less exaggerated and less protracted after yoga training (4). Our results suggest that the vasoconstrictor and cardiac acceleratory responses to IHG test are subnormal in hypertensive patients and yoga training improves these reflex regulatory mechanisms. This is an interesting observation and needs further study and confirmation.

ACKNOWLEDGEMENTS 

The authors wish to express their gratitude to the Central Council for Research in Yoga and Naturopathy (CCRYN) and Director, JIPMER, Pondicherry, for funding the Research Project.