Prof. J.P.N. Mishra
Cardiovascular disease (CVD) is the leading cause of death and disability in industrialized nations (Watkins, 2004), as well as in developing countries (Posner, 1994). Leading to premature morbidity and mortality, and to preventable losses of employment, earnings, and quality of life, CVD is clearly of pressing clinical and economic significance, underscoring the need for effective primary prevention efforts that target common, modifiable risk factors. Prominent among these are the physiologic and anthropometric risk factors associated with the insulin resistance syndrome (IRS), and the neuroendocrine and psychosocial alterations that may both predispose to and result from these IRS-related abnormalities.
Increased sympathetic activity, enhanced cardiovascular reactivity, and reduced parasympathetic tone have also been strongly implicated in the pathogenesis of IRS (Issoma, 2003) and in the development and progression of atherosclerosis (Rozanski, 1999) and cardiovascular disease (Gadegbeku, 2002). In addition, recent research offers compelling evidence that chronic psychological stress and negative affective states contribute significantly to the pathogenesis and progression of insulin resistance (Bjorntorp, 1997), glucose intolerance (Vitaliano, 2002), hypertension (Levenstein, 2001), dyslipidemia (Vitaliano, 2002; Levenstein, 2001), and other IRS-related conditions (Vonkanel, 2001; Bjorntorp, 1997) and ultimately, increase risk for CVD morbidity and mortality (Rozanski, 1999; Everson, 1997).
Not only can IRS-related conditions be exacerbated by lifestyle variables, such as smoking, lack of exercise, and poor diet, but also these conditions can interact with one another in a destructive manner (Davidson, 1991), likely accounting for their synergistic effect on CVD risk (Carr, 2003). Thus, a vicious cycle is initiated, which, as time goes on, becomes increasingly difficult to treat, highlighting the importance of early intervention.
In light of the strong influence of psychosocial factors on the development of both IRS and CVD, the role of sympathetic activation in the pathogenesis of insulin-resistant states, and the mutually exacerbating effects of these and other IRS-related risk factors, mind-body therapies may have considerable potential in the prevention and treatment of CVD. Of particular interest in this regard is yoga, an ancient mind-body discipline that has been widely used in India for the management of hypertension, diabetes, and related chronic insulin resistance conditions (Damodaran, 2002) and may hold promise as a therapeutic intervention and health promotion measure.
Pramanik (2009) studied immediate effect of slow pace bhastrika pranayama (respiratory rate 61 min) for 5 minutes on heart rate and blood pressure and the effect of the same breathing exercise for the same duration of time (5 minutes) following oral intake of hyoscine-N-butylbrorrtide (Buscopan), a parasympathetic blocker drug. Heart rate and blood pressure of volunteers (n = 39, age = 25-40 years) was recorded following standard procedure. First, subjects had to sit comfortably in an easy and steady posture (sukhasana) on a fairly soft seat placed on the floor keeping head, neck, and trunk erect, eyes closed, and the other muscles reasonably loose. The subject is directed to inhale through both nostrils slowly up to the maximum for about 4 seconds and then exhale slowly up to the maximum through both nostrils for about 6 seconds. The breathing must not be abdominal. After 5 minutes of this breathing practice, the blood pressure and heart rate again were recorded in the aforesaid manner using the same instrument. The other group (n = 10) took part in another study where their blood pressure and heart rate were recorded following half an hour of oral intake of hyoscine-N-butylbromide 20 mg. Then they practiced the breathing exercise as stated above, and the abovementioned parameters were recorded again to study the effect of parasympathetic blockade on the same pranayama. It was noted that after slow bhastrika pranayamic breathing (respiratory rate 6/min) for 5 minutes, both the systolic and diastolic blood pressure decreased significantly with a slight fall in heart rate. No significant alteration in both blood pressure and heart rate was observed in volunteers who performed the same breathing exercise for the same duration following oral intake of hyoscine-N-butylbromide. The study states that pranayama increases frequency and duration of inhibitory neural impulses by activating pulmonary stretch receptors during above tidal volume inhalation as in Hering Bruer reflex, which bring about withdrawal of sympathetic tone in the skeletal muscle blood vessels, leading to widespread vasodilatation, thus causing decrease in peripheral resistance and thus decreasing the diastolic blood pressure. After hyoscine-N-butylbromide, the parasympathetic blocker, it was observed that blood pressure was not decreased significantly as a result of pranayama, as it was observed when no drug was administered. It was concluded from the results that vagal cardiac and pulmonary mechanisms are linked, and improvement in one vagal limb might spill over into the other. Baroreceptor sensitivity can be enhanced significantly by slow breathing (supported by a small reduction in the heart rate observed during slow breathing and by reduction in both systolic and diastolic pressure). Slow pace bhastrika pranayama (respiratory rate 6/min) exercise thus shows a strong tendency to improving the autonomic nervous system through enhanced activation of the parasympathetic system
Upadhyay (2008) The responses of Alternate Nostril Breathing (ANB) the Nadisudhi pranayama on some cardio-respiratory functions were investigated in healthy young adults. The subjects performed ANB exercise (15 minutes every day in the morning) for four weeks. Cardio-respiratory parameters were recorded before and after 4-weeks training period. A significant increment in Peak expiratory flow rate (PEFR L/min) and Pulse pressure (PP) was noted. Although Systolic blood pressure (SBP) was decreased insignificantly, the significant decrease in pulse rate (PR), respiratory rate (RR), diastolic blood pressure (DBP) was shown from their studies. Results indicate that regular practice of ANB (nadisudhi) increases parasympathetic activity.
Granath et al (2006) compared the psychological and physiological benefits of a Kundalini yoga program and a stress management program based on cognitive behavior therapy principles. Participants in the both groups shared significant improvement in both psychological (self-rated stress and stress behavior as anger, exhaustion, quality of life) and physiological (blood pressure, heart rate, urinary catecholamine's, salivary Cortisol) outcomes. There was no significant difference between the two groups. The authors concluded that both "Cognitive behavior therapy and yoga are promising stress management techniques".
Harinath et al (2004) have studied the Effects of Hatha yoga and Omkar meditation on cardiorespiratory performance, psychological profile, and melanin secretion. They find that Yogic practices for 3 months resulted in an improvement in cardiorespiratory performance and psychological profile. The systolic blood pressure, diastolic blood pressure, mean arterial pressure, and orthostatic tolerance did not show any significant correlation with plasma melanin. However, the maximum night time melanin levels in yoga group showed a significant correlation (r = 0.71, p < 0.05) with well-being score. They conclude that yogic practices can be used as psychophysiology stimuli to increase endogenous secretion of melanin, which, in turn, might be responsible for improved sense of well-being.
Telles et al (2004) in another study determined whether yoga reduced heart rate and whether the reduction would be more after 30 days of yoga training. Two groups (yoga and control, n = 12 each) were assessed on Day 1 and on Day 30. During the intervening 30 days, the yoga group received training in yoga techniques while the control group carried on with their routine. At each assessment the baseline heart rate was recorded for one minute. This was followed by a six-minute period during which participants were asked to attempt to voluntarily reduce their heart rate, using any strategy. Both the baseline heart rate and the lowest heart rate achieved voluntarily during the six-minute period were significantly lower in the yoga group on Day 30 compared to Day 1 by a group average of 10.7 beats per minute (i.e., bpm) and 6.8 bpm, respectively. In contrast, there was no significant change in either the baseline heart rate or the lowest heart rate achieved voluntarily in the control group on Day 30 compared to Day 1.
Sinha et al (2004) measured energy cost and cardio respiratory changes during the practice of Surya Namaskar (SN). The pulmonary ventilation, carbon-dioxide output, oxygen consumption, HR and other cardio respiratory parameters were measured during the actual practice of SN. Oxygen consumption was highest in the eighth posture (1.22+/-0.073 1 min(-l)) and lowest in the first posture (0.35+/-0.02 1 min(-l)). Total energy cost throughout the practice of SN was 13.91 kcal and at an average of 3.79 kcal/min. During its practice highest HR was 101+/-13.5 b.p.m. As an aerobic exercise SN seemed to be ideal as it involves both static stretching and slow dynamic.component of exercise with optimal stress on the cardiorespiratory system.
Madanmohan et al (2004) studied modulation of cardiovascular responses to exercise by yoga training. Exercise produced a significant increase in HR, systolic pressure, RRP (Rate-pressure Product) and Do P (Double Product) and a significant decrease in diastolic pressure. After two months of yoga training, exercise induced changes in these parameters were significantly reduced. It is concluded that after yoga training a given level of exercise leads to a milder cardiovascular response, suggesting better exercise tolerance.
Barnes et al (2004) conducted a research study to assess the impact of meditation on resting and ambulatory blood pressure and heart of youths. They observed significant decrease in resting blood pressure, day time ambulatory blood pressure after school, and day time ambulatory heart rate after school. These finding demonstrated the potential beneficial impact of meditation on blood pressure and heart rate in the natural environment in healthy normotensive youth.
Madanmohan et al (2004) studied effect of six weeks of shavasan training on spectral measures of short-term heart rate variability in young healthy volunteers. This shows that shavasana training for 15 minutes a day, 4 days a week, for six weeks does not significantly affect heart rate variability in young healthy subjects.
Harinath et al (2004) in their study included thirty healthy men and they were randomly divided in two groups. Group 1 subjects served as controls and performed body flexibility exercises for 40 minutes and slow running for 20 minutes during morning hours and played games for 60 minutes during evening hours daily for 3 months. Group 2 subjects practiced selected yogic (postures) for 45 minutes. Yogic practices for 3 months resulted in an improvement in cardiorespiratory performance and psychological profile. The plasma melatonin also showed an increase after three months of yogic practices.
Mercuri et al (2003) carried out a scientific study with the aim to evaluate the clinical and metabolic changes in yoga practicing people with diabetes immediately and after practicing for 3 months. In that study it was concluded by the authors that the yoga practice brings about significant changes in blood pressure, heart rate and lipid profile of experimental group subject.
Udupa et al (2003) studied effect of pranayama training on cardiac function in normal young volunteers. For their study they selected few students. Pranayama group subjects were given training in nadishuddhi, mukh-bhastrika,pranav and savitripranayamas and practiced the same for 20 minutes daily for duration of 3 months. Other group subjects were not given any pranayama training. Pranayama training produced an increase in RR interval variation (RRIV) and a decrease in QT1 / QS2> suggesting an enhanced parasympathetic and blended sympathetic activity respectively. QS, PEP and PEP/LVET increased significantly, whereas LEVT was reduced significantly in pranayama group. In contrast, the changes in STI and AFT were much less marked in the control group To conclude, the study showed that three months of pranayama training modulates ventricular performance by increasing parasympathetic activity and decreasing sympathetic activity. Cheng et al (2003) evaluated heart rate recovery following maximal exercise testing as a predictor of cardiovascular disease and all-cause mortality in men with diabetes. Heart rate recovery (HRR) is an independent prognostic indicator for cardiovascular disease (CVD) and all-cause mortality in healthy men. They examined the association of HRR to CVD-related and all-cause mortality in men with diabetes, and reported asymmetrical ratio in cardiovascular diseases and mortality rates.
Khadket al (2003) recorded the effect of yoga on blood pressure response in stimulus and found the relevant and significant reduction in blood pressure of experimental group of subjects.
Barashankar et al (2003) conducted a study to examine the effect of yoga on cardiovascular function in subjects above 40 yrs of age. Pulse rate, systolic and diastolic blood pressure and valsalva ratio were studied in 50 control subjects (not doing any type of physical exercise) and 50 study subjects who had been practicing yoga for 5 years. From the study it was observed that significant reduction in the pulse rate occurs in subjects practicing yoga (PcO.OOl). The difference in the mean values of systolic and diastolic blood pressure between study group and control group was also statistically significant (PcO.Ol and P<0.001 respectively). The systolic and diastolic blood pressure showed significant positive correlation with age in the study group (rl systolic= 0.631 and rl diastolic = 0.610) as well as in the control group (r2 systolic = 0.981 and r2 diastolic = 0.864). The significance of difference between correlation coefficient of both the groups was also tested with the use of Z transformation and the difference was significant (Z systolic= 4.041 and Z diastolic^ 2.901). Valsalva ratio was also found to be significantly higher in yoga practitioners than in controls (P<0.001). Results indicate that yoga reduces the age related deterioration in cardiovascular functions.
In the light of their extensive study Madanmohan et al (2002) stated that the shavasan is known to enhance one's ability to combat stressful situations. They planned to determine if shavasan could modulate the'physiological response to stress induced by cold pressor test (CPT) and the possible mechanisms involved. Ten normal adults were taught shavasan and practiced the same for a total duration of seven days. RR interval variation (RRIV), deep breathing difference (DBD), and heart rate, blood pressure and rate-pressure-product (RPP) response to CPT were measured before and immediately after shavasan. Shavasan produced a significant increase in DBD and an appreciable but statistically insignificant increase in RRIV suggesting an enhanced parasympathetic activity. Significant blunting of cold pressure induced increase in heart rate, blood pressure and RPP by shavasan was seen during and even five minutes after CPT suggesting that shavasan reduces the load on the heart by blunting the sympathetic response. It is concluded that shavasan can enhance one's ability to withstand stress induced by CPT and this ability can be achieved even with seven days of shavasan training.
Roopakala et al (2002) have observed significant reduction in the systolic blood pressure following Pranayama.
Vyas et al (2002) in another scientific study demonstrated that respiratory and cardiovascular functions and lipid profile of those practicing Raj yoga Meditation (short and long term duration) were compared with those of non-meditators. Lipid profile showed a significant lowering of serum cholesterol in short term and long term meditators as compared to non-meditators. Lipid profile of short and long term meditators was better than the same of non-meditators in-spite of similar routine physical activities. Vital capacity, tidal volume and breath holding were significantly higher in short and long term meditators than non-meditators. Diastolic blood pressure was significantly lower in both short and long term meditators. Heart rate was significantly lower in long term meditators than short term meditators. This proves that Raja yoga Meditation brings in significant improvement in lipid profile along with respiratory and cardiovascular parameters.
Damodaran et al (2002) observed twenty patients with mild to moderate essential hypertension underwent yogic practices daily for one hour for three months. Results showed decreased blood pressure, blood glucose, cholesterol and triglycerides and improved subjective well-being and quality of life.
Jyotsana et al (2001). Studied the effect of yoga on cardiovascular system in subjects above 40 years. It was observed that significant reduction in the pulse rate occurs in subjects practicing yoga (p<0.001). The difference in the mean values of systolic and diastolic blood pressure between study group and control group was also statistically significant. The systolic and diastolic blood pressure showed significant positive correlation with age in the study group as well as in the control group. To conclude that cardiovascular parameters alters with age but these alterations are slower in persons aging with yoga.
Arambula et al (2001) in their study explored the physiological correlates of a highly experienced Kundalini yoga meditator. Thoracic and abdominal breathing patterns, heart rate (HR), occipital and parietal electroencephalograph (EEG), skin conductance level (SCL), and blood volume pulse (BVP) were monitored during prebaseline, meditation, and postbaseline periods. Visual analyses of the data showed a decrease in respiration rate during the meditation from a mean of 11 breaths/min for the pre- and 13 breaths/min for the postbaseline to a mean of 5 breaths/min during the meditation, with a predominance of abdominal/diaphragmatic breathing. There was also more alpha EEG activity during the meditation (M = 1.71 microV) compared to the pre- (M =.47 µV) and postbaseline (M =.78 µV) periods, and an increase in theta EEG activity immediately following the meditation (M =.62 µV) compared to the pre-baseline and meditative periods (each with M =.26 µV). These findings suggest that a shift in breathing patterns may contribute to the development of alpha EEG.
Raichur et al (2001) showed in their study that significant reduction in Resting Heart Rate (RHR) diastolic blood pressure, respiratory rate, minute volume anxiety scores and increase in tidal volume were recorded after regular practice of meditation.
Barnes et al (2001) examined the impact of the Transcendental Meditation (TM) program on cardiovascular (CV) reactivity in adolescents with high BP. Thirty-five adolescents [ages 15-18 years] with resting systolic blood pressure (SBP) between the 85th and 95th percentile for their age and gender on three consecutive occasions, were randomly assigned to either TM (n=17) or health education control (CTL, n=18) groups. The TM group engaged in 15-min meditation twice each day for 2 months including sessions during school lunch break. Primary CV outcome measures were changes in blood pressure (BP), heart rate (HR), and cardiac output (CO) at rest and in response to two laboratory stressors, a simulated car driving stressor and an interpersonal social stressor interview. The TM group exhibited greater decreases in resting SBP (P<.03) from pre- to post-intervention, compared to the CTL group. The TM group exhibited greater decreases from pre- to post-intervention in SBP, HR, and CO reactivity (Pc.03) to the simulated car driving stressor, and in SBP reactivity (P<.03) to the social stressor interview. The TM program appears to have a beneficial impact upon CV functioning at rest and during acute laboratory stress in adolescents at-risk for hypertension.
Bernardi et al (2001) conducted a study to test whether rhythmic formulas suoh as the rosary and yoga mantras can synchronise and reinforce inherent cardiovascular rhythms and modify bar reflex sensitivity. Comparison of effects of recitation of the Ave Maria (in Latin) or of a mantra, during spontaneous and metronome controlled breathing, on breathing rate and on spontaneous oscillations in respiratory rate interval, and on blood pressure and cerebral circulation. Breathing rate, regularity of breathing, bar reflex sensitivity, frequency of cardiovascular oscillations were the main variables of observation. Both prayer and mantra caused striking, powerful, and synchronous increases in existing cardiovascular rhythms when recited six times a minute. Bar reflex sensitivity also increased significantly, from 9.5 (SD 4.6) to 11.5 (4.9) ms/mm Hg, P<0.05. Rhythm formulas that involve breathing at 9 breaths per minute induce favourable psychological and possibly physiological effects.
Murugesan et al (2000) assessed thirty-three hypertensive, on systolic and diastolic blood pressure, pulse rate and body weight. The subjects were randomly assigned to three groups: a yoga group, a group who received medical treatment by the physician and a control group. Yoga was offered in the morning and in the evening for 1 hr/session for 11-weeks. Medical treatment comprised drug intake every day for the experimental period. The result of pre-post tests revealed that both the treatment stimuli (i.e., yoga and drug) were effective in controlling the measures of hypertension
Lehrer et al (1999) in their study examined the effects of Tanden Breathing 'by Zen practitioners on cardiac variability. Tanden breathing involves slow breathing into the lower abdomen. Eleven Zen practitioners, six Rinzai and five Soto, were each studied during 20 minutes of tanden breathing, preceded and followed by 5-minute periods of quiet sitting. During this time, we measured heart rate and respiration rate. For most subjects, respiration rates fell to within the frequency range of 0.05 to 0.15 Hz during tanden breathing. Heart rate variability significantly increased within this low-frequency range but decreased in the high-frequency range (0.14-0.4 Hz), reflecting a shift of respiratory sinus arrhythmia from high-frequency to slower waves. Rinzai practitioners breathed at a slower rate and showed higher amplitude of low frequency heart rate waves than observed among Soto Zen participants.
One rinzai master breathed approximately once per minute and showed an increase in very-low frequency waves (<0.05 Hz). Total amplitude of heart rate oscillations (across frequency spectra) also increased. More experienced Zen practitioners had frequent heart rhythm irregularities during and after the nadir of heart rate oscillations (i.e., during inhalation). These data are consistent with the theory that increased oscillation amplitude during slow breathing is caused by resonance between cardiac variability caused by respiration and that produced by physiological processes underlying slower rhythms. The rhythm irregularities during inhalation may be related to inhibition of vagal modulation during the cardio-acceleratory phase. It is not known whether they reflect any cardio-pathology.
Peng et al (1999) reported extremely prominent heart rate oscillations associated with slow breathing during specific traditional forms of Chinese Chi and Kundalini yoga meditation techniques in healthy young adults. They applied both spectral analysis and a novel analytic technique based on the Hilbert transform to quantify these heart rate dynamics. The amplitude of these oscillations during meditation was significantly greater than in the pre-meditation control state and also in three non-meditation control groups: i) elite athletes during sleep, ii) healthy young adults during metronomic breathing, and iii) healthy young adults during spontaneous nocturnal breathing. This finding, along with the marked variability of the beat-to-beat heart rate dynamics during such profound meditative states, challenges the notion of meditation as only an autonomic ally quiescent state.
Raghuraj (1998) studied effect of two selected yogic breathing techniques of heart rate virility. 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). 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 psycho-physiological measure than heart rate alone.
Bowman et al (1997) observed the effects of aerobic exercise training and yoga, a non-aerobic control intervention, on the baroreflex of elderly persons. Baroreflex sensitivity was quantified by the alpha-index, at high frequency (reflecting parasympathetic activity) and mid-frequency (reflecting sympathetic activity as well), derived from spectral and cross-spectral analysis of spontaneous fluctuations in heart rate and blood pressure. Twenty-six (10 women) sedentary, healthy, normotensive elderly (mean age 68 years) subjects were studied. Fourteen (4 women) of the sedentary elderly subjects completed 6 weeks of aerobic training, while the other 12 (6 women) subjects completed 6 weeks of yoga. Heart rate decreased following yoga but not after aerobic training. V02 max increased by 11 % following yoga and by 24% following aerobic training. No significant change in alpha medium frequency or alpha high frequency occurred after aerobic training. Following yoga, alpha HF but not alpha MF increased. Heart rate variability (HRV) was studied in cyclic meditation (CM) and supine rest (SR). CM included yoga postures followed by guided relaxation. Forty-two male volunteers were assessed in CM and SR sessions of 35 minutes, where CM or SR practice was preceded and followed by 5 minutes of SR. During the yoga postures of CM and after CM, low frequency power and the low frequency to high frequency power ratio decreased, whereas high frequency power increased. Heart rate increased during the yoga postures and decreased in guided relaxation and after CM. There was no change in SR. Hence, it appeared that predominantly sympathetic activation occurred in the yoga posture phases of CM while parasympathetic dominance increased after CM.
