Prof. J.P.N. Mishra
The findings of the present study indicated a significant decrease in Blood Pressure after three months in the subjects practicing Yoga and this decline persists even after six months of the practice. After further analysis it was observed that both the systolic and diastolic components of blood pressure and also mean pressure have shown the similar trend. Several studies have reported a beneficial effect of yoga based programs. These include eight uncontrolled studies of healthy (Joseph et al, 1981) and hypertensive adults (Lakshmikanthan et al, 1989), all but one of which (Patel, 1976) were conducted in India. Most of these studies were small, with only three (Telles et al, 1993) including twenty-five participants or more. Among nonrandomized controlled trials, nine studies of healthy adults (Udupaet al, 1975) and adults with hypertension (Latha, 1991) and/or Coronary artery disease (CAD) (Yogendra et al, 2004) have demonstrated significant reductions in blood pressure among participants who completed a yoga-based intervention relative to controls receiving an exercise (Bagga and Gandhi, 1983), enhanced usual care, or no intervention. Likewise, eleven RCTs of healthy adults (Harinath et al, 2004) and patients with hypertension or other Cardiovascular disease (CVD) risk factors (Broota et al, 1995) have demonstrated significant blood pressure declines among subjects receiving a yoga-based intervention versus controls receiving usual care (Patel et al, 1975), enhanced usual care with diet and exercise (Harinath et al, 2004), social contact, placebo therapy (Patel et al, 1988), or no active intervention (Ray et al, 2001). In a study of ninety five female Japanese university students, Cusumano and colleagues demonstrated comparable and significant reductions over time in blood pressure among women receiving three weekly training sessions in either Hatha yoga or progressive muscle relaxation (Cusumano et al, 1992). Overall, these studies demonstrated a 4.9% to 24.2% decline in diastolic blood pressure and a 2.6% to 21.3% decline in systolic blood pressure with yoga, with the magnitude of change varying with the study design and sample population. Yoga-based programs used in the twenty eight studies reporting positive findings ranged in duration from thirty days to six months (Sundar et al, 1984) in the uncontrolled studies, from three weeks (Selvamurthy et al, 1998) to six months (Stone et al, 1976) in the controlled nonrandomized studies, and from eight days to twelve months (Fields et al, 2002) in the RCTs. Interventions associated with blood pressure improvement included yoga routines both alone (N = 20) and in combination with other therapies (N = 8). Of those studies using yoga alone, ten incorporated active yoga asanas and ten used relaxation postures alone (Sundar et al, 1984) or in combination with meditation (Patel et al, 1975). Collectively, the findings of both controlled and uncontrolled studies suggest that even the relatively short-term practice of yoga, meditation or other yoga-based programs may reduce blood pressure. Our findings are also in the same line.
Recently a randomized control study reported that device guided slow breathing (mechanized modulation of breathing) with prolong expiration performed daily for two months resulted in a sustained blood pressure reduction of 16.2/10.6 mmHg from a baseline blood pressure of 158/97 mmHg (Schein et al, 2000)
Herbert Benson (1975) report that the subjects lower the systolic blood pressure during sessions. Later another study on same pattern involving home blood pressure measurements conducted by Grossman et al (2000) have reported that breathing exercises play a prominent role in reduction of blood pressure. According to another author yoga, meditation and biofeedback have had some success in treating high blood pressure (Irvine et al 1986).
Neumerous other longitudinal studies on effect of yoga on cardiovascular system in various age groups have shown a significant and positive coefficient of correlation of systolic and diastolic blood pressure with age, where mean values of pulse rate, systolic blood pressure and valsalva ratio were less in the group of subjects practicing yoga in comparison to control group of subjects. The author stated (Gopal et al, 1973) that variety of behavioural factors such as stress and anxiety related to daily life activities and affective and attitudinal dispositions of the individual influence the cardiovascular responses. Yogic exercises involving physical, mental and spiritual task bring in several behavioural changes. Yoga affects hypothalamus and brings about decrease in the systolic and diastolic blood pressure through its influence on vasomotor center, which leads to reduction in sympathetic tone and peripheral resistance (Khanam et al, 1996)
Mishra and Shekhawat (2007) have conducted a scientific study to determine if meditation training modulates the cardiovascular response and autonomic functions, after short term yoga and meditation intervention program which combined daily practice of Kayotsarga (Relaxation with self-awareness), Antaryatra (Internal Trip) and Anupreksha (Contemplation) (components of Preksha Meditation). They observed that such short term meditational intervention has reduced systolic and diastolic blood pressure, which they attributed to reduction in sympathetic activity.
By far the most important part of autonomic nervous system for regulation of the cardiovascular responses in the sympathetic nervous system. Sympathetic vasomotor nerve fibers leave the spinal cord and pass into the sympathetic chain and then by two roots to the circulation: (1) through specific sympathetic nerves that innervate mainly the vasculature of the internal viscera and the heart and (2) through the spinal nerves that innervate mainly the vasculature of the peripheral areas. The innervation of the smaller arteries and arterioles allows sympathetic stimulation to increase the resistance and thereby to change the rate of blood flow and blood pressure. The parasympathetic nervous system, although play a minor role in regulation of circulation, its most important circulatory effect is its control of heart rate by way of parasympathetic fibers carried to the heart in the vagous nerve. Principally parasympathetic stimulation causes a marked decrease in heart rate, blood flow and blood pressure (Guyton, 1991).
Yoga practices stimulate the autonomic nervous system by enhancing and strengthening the functioning of parasympathetic component and simultaneously supporting the sympathetic components (Acharya Mahaprajna, 1994). Thus it may be inferred that our findings are in conformity with the pathway of mechanism of action of yoga and meditation.
