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Chapter 2:
Physiological Effects
by Michael Murphy and Steven Donovan
[While meditation can be considered as a cognitive strategy by which consciousness gains control over normally non-conscious states of awareness, including involuntary bodily processes, the physiology of meditation has received more attention than any other subject from Western scientists quite out of proportion to all other dimensions of meditative experience.
Historically, this is largely because, for three hundred years, the dualism of Descartes has required an absolute separation of mind and body, while its handmaiden and more recent dictum of research, scientific positivism, asserts mechanistically that what is immediately physical and material constitutes all there is to reality. Hence, the most visible and palpable form of a phenonenon is the only proper object of scientific scrutiny.
Modern researchers, by virtue of the fact that they are engaged in applying the methods of reductionistic science, even as they apply such methods to seemingly disreputable topics, cannot avoid these constraints. Thus the physiology of meditation has been the starting point and remains at the center of most research efforts. Ed.]
The Cardiovascular System
Heart Rate
Many contemporary studies have indicated that the heart rate usually slows in quiet meditation and quickens during active disciplines or moments of ecstasy, as we would expect from contemplative writings that describe the calming effect of silent meditation [31] and the stimulation of exercises such as Tantric visualization or devotional chanting. [32]
Most studies of Transcendental Meditation (TM), Zen Buddhist sitting, Herbert Benson's "relaxation response," and other calming forms of meditation indicate that meditating subjects generally experience a lowering of the heart rate. The results of such studies vary to some degree, since they depend on different kinds of subject groups and various experimental procedures, with some showing an average decline of seven beats or more per minute among their subjects and some showing two or three beats per minute among some of their subjects. Bagga and Gandhi (1983) found an average decline as high as fifteen beats per minute among some of their subjects. Some studies indicate that meditation lowers the heart rate more than biofeedback, progressive relaxation, other therapies, or simple sitting, while other studies indicate that these various activities have an equivalent effect on the heart rate. Once again, such differences in outcome can be accounted for by differences among subjects and experimental designs.
A decline in heart rate is more pronounced among experienced meditators, according to a few studies, though here too the evidence is not unanimous. The only generalization we can make safely now is that some subject groups demonstrate an average lowering of heart rate during meditation, and that some experienced individuals may achieve a permanent lowering of the heart rate with continued practice.
In studies involving active methods such as rapid breathing, though, the heart rate has risen. Such studies suggest that patterns of physiological activity are specific to particular practices.
Julian Davidson (1976), Roland Fischer (1971, 1976), and other researchers have distinguished excitatory from relaxing forms of meditation, associating their effects with the ergotropic and trophotropic conditions of the central nervous system modeled by Gelhorn and Keily (1972). Fischer (1971) has said that the extreme trophotropic state of samadhi sometimes triggers an extreme ergotropic reaction, which may be ecstatic, so that the physiological effects of contemplative activity show wide variability.
The following studies show a decrease in heart rate during meditation. Bono (1984) found that the reduction of heart rate during TM was greater than the reduction resulting from sitting quietly with eyes closed. Delmonte (1984f) found that heart rates were slightly lower during meditation than rest for fifty-two subjects. Holmes et al. (1983), however, found that while meditators had lower heart rates while practicing TM, they did not experience lower arousal than control subjects who were simply resting. See follow-up discussion, particularly Dillbeck and Orme-Johnson (1987), Morrell (1986), and Holmes (1984).
Bagga and Gandhi (1983) compared groups of six TM practitioners and six Shavasana practitioners (relaxing while lying on one's back) with six controls, and found significantly reduced heart rates for both experimental groups versus the control group. Cummings (1984) observed reduced heart rates for those practicing a combination of meditation and exercise. Throll (1982) found that a Transcendental Meditation group displayed a more significant decrease in heart rate than a group using Jacobson's progressive relaxation.
Pollard and Ashton (1982) divided sixty subjects into six groups in a comparison of heart rate decrease obtained by visual feedback, auditory feedback, combined visual and auditory feedback, instructions to decrease heart rate without biofeedback, sitting quietly, and abbreviated relaxation training. A comparison group of meditators with a minimum of six years of experience was also studied. The results indicated that there was no advantage of a heart rate decrease task for subjects receiving visual, auditory, or combined biofeedback, though all groups showed evidence of a decline in heart rate over the testing session. The meditation group showed the greatest overall decline, with a decrease in heart rate of approximately seven beats per minute, versus three beats per minute for the groups using biofeedback techniques.
Cuthbert et al. (1981) had results demonstrating clear superiority for meditators using Benson's relaxation response versus heart rate biofeedback, especially when the subject experimenter relationship was supportive. Lang et al. (1979) placed the heart rate decrease for advanced TM meditators with more than four years of practice at 9%. Bauhofer (1978) found that the heart rates of experienced TM meditators were lowered by TM more than those of less experienced TM meditators. Corey (1977) and Routt (1977) reported that Transcendental Meditation appeared to decrease heart rate under nonstress conditions. Glueck and Stroebel (1975), Wallace and Benson (1972), Wallace et al. (1971c), and Wallace (1971) found that the heart rate decreased from three to five beats per minute during Transcendental Meditation. Reports of reduced heart rates during meditation extend back to Paul (1969), Karambelkar et al. (1968), Anand and Chhina (1961), Wenger and Bagchi (1961), Bagchi and Wenger (1957), and Das and Gastaut (1955).
Kothari et al. (1973) reported the case of a yogi who was confined to a small underground pit for eight days and continuously monitored with an EKG. From the second day until the eighth, EKG activity was below a recordable level, indicating that the yogi had either stopped his heart or greatly decreased its electrical activity. The authors believe that the yogi could not have tampered with the EKG leads without creating an obvious electrical disturbance.
Some studies indicate that heart rates increase under certain circumstances, such as deeply absorbed trance (samadhi) [see Lehrer et al. (1980), Parulkar et al. (1974), Wenger and Bagchi (1961), and Das and Gastaut (1955)]. Other research shows no consistent changes in heart rate with the practice of Ananda Marga Yoga or progressive relaxation [see Gash and Karliner (1978), Elson et al. (1977), Travis et al. (1976), Wenger et al. (1961), and Bagchi and Wenger (1957)].
We could not find accounts in the traditional literature describing the number of heartbeats one should expect during meditation, with which we could compare the numbers in modern studies. Contemplative masters did not share the scientific passion for quantitative analysis and generally appreciated the differences in physiology and temperament among their followers. They also did not have the means to measure bodily changes precisely, and generally wouldn't have used them if they had.
Redistribution of Blood Flow
Blood flow is directly or indirectly manipulated for mental clarity, health, increased energy, or the promotion of religious emotion through hatha yoga postures, breathing exercises, prostrations, tai chi movements, dervish dancing, and other activities associated with the contemplative traditions. Traditional teachers could not measure blood flow with scientific exactness, of course, but some of them could skillfully guide their students' practice through empathy, intuition, and kinesthetic feel, and in doing so they sometimes looked for bodily signs related to blood circulation, such as flushing of the face and chest and changes in skin tone and complexion. [33] The picture of meditation's effect on blood flow provided by modern studies is quite preliminary, though. Most of it comes from TM-sponsored research.
Delmonte (1984f) tested fifty-two subjects and found that meditators showed a significantly greater increase in digital blood volume during meditation than rest. Jevning, Wilson, and O'Halloran (1982) studied muscle and skin blood flow and metabolism during states of decreased activation in TM. They concluded that acute decline of forearm oxygen consumption has been observed during an acute, wakeful behaviorally induced rest/relaxation state. This change of tissue respiration was not associated with variation of rate of forelimb lactate generation. Since forearm blood flow did not change significantly during this behavior, the decline of oxygen consumption by forearm was due almost solely to decreased rate of oxygen extraction. Decreased muscle metabolism was a likely contributor to these observations. The occurrence of sleep was not related to the metabolic change. The lack of coupling between the metabolic and blood flow changes during this state of decreased activation suggests limitation of the hypothesis of obligatory coupling between systemic and/or regional cardiovascular and metabolic function.
Earlier, Jevning and Wilson (1978) reported that TM increased cardiac output among twenty-seven subjects by an average of 16% (ml/min measured by dye dilution methods), decreased hepatic blood flow by an average of 34% (ml/min measured by clearance methods), and decreased renal blood flow by an average of 29% (ml/min measured by clearance methods), suggesting an increase of approximately 44% in the nonrenal, nonhepatic component of blood flow (versus an increase of approximately 12% for an eyes-closed rest-relaxation control group). Increased cerebral or skin blood flow may account for part of this redistribution.
Jevning et al. (1976) found an average 15% increase in cardiac output, an average 20% decline in liver blood flow, and an average 20% decrease in renal blood flow among a group of six meditators practicing TM. A control group of six showed no change in cardiac output and liver blood flow, and a significant decline in renal blood flow. The authors believe that decreased skin and muscle blood flow was suggested by other, indirect data, and that since cardiac output increases and all measured organ blood flows decrease, it is possible that cerebral perfusion increases markedly during TM. Jevning et al.'s findings were a surprise because earlier studies had indicated a decrease in cardiac output of 25% during TM (versus a decrease of about 20% in deep stage-four sleep) [see Wallace (1970)].
Wallace et al. (1971a) speculated that the fall in blood lactate during meditation might be due to increased skeletal muscle blood flow with consequent increased aerobic metabolism. These researchers referred to Riechert (1976), who recorded forearm blood flow increases of 30% with unchanged finger blood flow (using a plethysmograph). Jevning and Wilson (1978) found that frontal cerebral blood flow increased an average of 65% during TM for ten teachers of the technique (five to eight years of regular practice), and remained elevated afterwards, with brief increases up to 100-200% (measured by quadripolar rheoencephalography). Levander et al. (1972) measured forearm blood flow (using a water plethysmograph) in five subjects 180 times and reported that the pretest period mean blood flow of 1.41 ml/100ml tissue volume/min increased to 1.86 ml/100ml tissue volume/min during TM, and returned to pretest values during post-testing. Wallace and Benson (1972) found an increase in forearm blood flow of 32% for their TM subjects.
Blood Pressure and Hypertension
There is strong evidence that meditation helps lower blood pressure in people who are normal or moderately hypertensive. This finding has been replicated by more than nineteen studies, some of which have shown systolic reductions among their subjects of 25 mmHg or more. In some studies a combination of meditation with biofeedback or other relaxation techniques proved to be more effective than meditation alone for some subjects. Several studies, however, have shown that relief from high blood pressure diminishes or disappears entirely if meditation is discontinued, and few people with acute hypertension have experienced lower blood pressure in experiments of this kind.
At the time of this writing, speculation regarding the mechanisms mediating meditation's beneficial effects on high blood pressure appears to be inconclusive. Meditation often helps relax the large muscle groups pressing on the circulatory system in various parts of the body. It might also help relax the small muscles that control the blood vessels themselves; when that happens, the resulting elasticity of blood vessel walls would help reduce the pressure inside them. Other mechanisms may be involved, which further research will reveal. The following studies explored meditation's effect on blood pressure and hypertension:
Cort (1989) It was hypothesized that the large the variability of results in different studies on the effect of meditation on hypertension may be due to differences in compliance to the meditation regimens. This study of fifty-one black adults supports the claim that greater compliance to a meditation program leads to greater decreases in blood pressure.
Delmonte (1984f) Forty nonmeditators and twelve experienced Transcendental Meditators were randomly assigned to four experimental cells devised to control for order and expectation effects. All fifty-two (female) subjects were continuously monitored in seven physiological measures during both meditation and rest. Each subject was her own control in an experiment comparing meditation to rest. Analysis of variance on change scores calculated from both initial and running (intertrial) baselines revealed small but significant condition effects for all variables except diastolic BP. With respect to systolic BP, the nonmeditators showed a significantly larger drop from initial baseline during meditation than during rest. With respect to running baseline, the meditators demonstrated a significantly smaller increase in systolic blood pressure with the complete trial data and a greater decrease with the end-of-trial data during meditation than during rest.Wallace et al. (1983b) This study measured systolic blood pressure using a standard mercury sphygmomanometer on 112 transcendental meditators. The subjects had a mean systolic blood pressure 13.7 to 24.5 less than the population mean. The analysis also showed that meditators with more than five years of experience had a mean systolic blood pressure 7.5 lower than meditators with less than five years of experience.
Bagga and Gandhi (1983) The authors studied a group of eighteen people who were equally divided into a TM, Shavasana (relaxing while lying on one's back), or control group. After twelve weeks of practicing, the TM and Shavasana groups showed significant declines in systolic blood pressure as high as 10 mmHg, whereas the control group demonstrated no decline.
Hafner (1982) Twenty-one hypertension patients who had been randomly assigned to eight one-hour sessions of either meditation training, meditation plus biofeedback-aided relaxation, or a nontreatment control group were studied. Statistically significant falls in systolic and diastolic blood pressure occurred after both training programs, although overall reductions in blood pressure were not significantly greater in either program than in the control group. Meditation plus biofeedback-aided relaxation produced falls in diastolic blood pressure earlier in the training program than did meditation alone. All patients practiced meditation regularly between training sessions, but the amount of practice did not correlate with the amount of blood pressure reduction after training.
Seer and Raeburn (1980) Forty-one unmedicated hypertensives were randomly assigned to three groups: TM training, placebo control (TM training without a mantra), and no-treatment control. The results showed modest reductions in blood pressure in both treatment groups, compared with no treatment, with diastolic percentage reductions reaching significance. There was considerable subject variation in response, with an overall mean decline in diastolic blood pressure of 8-10% on a three-month follow-up.
Surwit et al. (1978) This study compared the separate effects of three procedures for the reduction of high blood pressure in three treatment groups of eight patients, each with medically verified borderline hypertension. The three treatment groups used the following procedures: (a) biofeedback for simultaneous reductions in systolic blood pressure and heart rate; (b) biofeedback for reductions in integrated forearm and frontalis muscle electromyographic activity; and (c) meditation relaxation based on the relaxation response procedure developed by Herbert Benson. Each patient was studied in two baseline sessions, eight training sessions, and a six-week follow-up. Half of the sample returned for a one-year follow-up. Analysis of variance of the three treatment groups over eight training sessions, with twenty trials per session, revealed significant effects for trials within sessions. However, there were no significant main effects or interactions related to differences between the treatment conditions or to changes in blood pressure over the course of training sessions. Although all groups showed moderate reductions in blood pressure as compared to initial values, no technique could be seen to produce a reduction in pressure greater than that observed in the baseline sessions. Blood pressures of patients reporting for the one-year follow-up were not different from pretreatment baseline levels.
Pollack et al. (1977) Twenty hypertensive patients, nine of whom were on stable dosages of hypotensive medication, were taught TM. Blood pressure reductions were 10 mmHg systolic/2 mmHg diastolic after three months and 6 mmHg systolic/2 mmHg diastolic after six months. The only statistically significant reduction in blood pressure occurred after three months. Meditation plus biofeedback produced decreases in diastolic blood pressure earlier in the training program than meditation alone.
Simon et al. (1977) Five borderline hypertensives were taught TM. After they learned the technique and practiced it for an average of thirty-two weeks, their mean blood pressure decreased from 153/101 mmHg to 138/92 mmHg.
Blackwell et al. (1976) Seven subjects on stable dosages of hypotensive medication were taught TM over a nine-to-twelve week period. They recorded a mean blood pressure reduction of 4 mmHg systolic/2 mmHg diastolic, and 3 mmHg systolic/4 mmHg diastolic during a follow-up six months later, but there were changes in drug treatment during the follow-up period.
Stone and DeLeo (1976) Fourteen hypertensives were taught a "Buddhist" meditation that involved counting breaths in five twenty-minute training sessions over six months. Five hypertensives were used as controls. While supine, the treatment group had mean blood pressure reductions of 9 mmHg systolic/8 mmHg diastolic. While upright, the treatment group had mean blood pressure reductions of 15 mmHg systolic/10 mmHg diastolic. While supine, the control group had mean blood pressure reductions of 1 mmHg systolic/2 mmHg diastolic. While upright, the control group had mean blood pressure reductions of 2 mmHg systolic/0 mmHg diastolic.
Patel and North (1975) Thirty-four hypertensive patients were assigned at random either to six weeks of treatment by yoga relaxation methods with biofeedback or to placebo therapy (general relaxation). Both groups showed a reduction in blood pressure (from 168/100 to 141/84 mmHg in the treated group and from 169/101 to 160/96 mmHg in the control group). The difference was highly significant. The control group was then trained in yoga relaxation, and the blood pressure fell to that of the other group (now used as controls).
Patel (1975a) Thirty-two patients—twenty-one females and eleven males—between the ages of thirty-four and seventy-five years with essential hypertension of known duration from six months to thirteen years, were randomly divided into a treatment group and a control group. Fourteen patients in the treatment group and fifteen in the control group were receiving antihypertensive drugs. Baseline blood pressure was first obtained after a twenty-minute rest in the supine position. The patients were given two stress tests: an exercise test (climbing a nine-inch step twenty-five times) and a cold pressor test (immersing the left hand in cold water after alerting the patient sixty seconds in advance) at the beginning and again after six weeks. Blood pressure was taken during the alert, at the end of each test, and every five minutes until it returned to the original value or up to a maximum of forty minutes. In the six weeks between test periods, all patients attended a twice-weekly clinic. The treatment group was given training in relaxation and meditation based on yogic principals, which was reinforced with biofeedback instruments, and group members were asked to practice relaxation and meditation at home twice daily for twenty minutes. In the treatment group there was a significant reduction in the pressure rises as well as in recovery time. Mere repetition of the tests did not influence these indications of stress. When the differences between the groups were compared, all measurements except the systolic pressure rise after exercise showed significant improvement in the treated group.
Patel (1975b) Twenty hypertension patients, nineteen of whom were using hypotensive drugs, were taught yoga, breath meditation, muscle relaxation, and meditation concentration. Their average blood pressure was reduced from 159.1/100.1 mmHg to 138.7/85.9 mmHg. The average blood pressures of twenty control subjects, eighteen of whom were using hypotensive drugs, who rested on a couch for the same number of sessions and were given no relaxation training, was reduced from 163.1/99.1 mmHg to 162.6/97.0 mmHg.
Patel (1975c) Twenty hypertensive patients treated by psychophysical relaxation exercises were followed up monthly for twelve months. Age- and sex-matched hypertensive controls were similarly followed up for nine months. Statistically significant reductions in blood pressure (BP) and antihypertensive drug requirements were satisfactorily maintained in the treatment group. Mere repetition of BP measurements and increased medical attention did not in themselves reduce BP significantly in control patients.
Benson et al. (1974d) Twenty-two borderline hypertensives not using drugs were taught TM, and their mean blood pressure decreased from 146.5/94.6 mmHg during the premeditation control period, lasting 5.7 weeks, to 139.6/90.8 mmHg during the postmeditation experimental period, lasting an average of twenty-five weeks. They were tested throughout the premeditation and postmeditation periods.
Benson et al. (1974f) Fourteen hypertension patients on drugs were taught the relaxation response. During a control period of 5.6 weeks, blood pressure did not change significantly from day to day, and averaged 145.6/91.9 mmHg. During an experimental period of twenty weeks, blood pressure decreased to 135.0/87.0 mmHg.
Patel (1973) Twenty hypertension patients using hypotensive drugs were taught yoga, breath meditation, muscle relaxation, and meditation concentration. Their average blood pressure was reduced from 159.1/100.1 mmHg to 138.7/85.9 mmHg. The average blood pressure of twenty control subjects, who rested on a couch for the same number of sessions and who were given no relaxation training, was reduced from 163.1/99.1 mmHg to 162.6/97.0 mmHg.
Deabler et al. (1973) In this study three groups of hypertensive patients were tested. Six subjects, who were taught progressive relaxation and hypnosis in eight to nine sessions over four to five days, had average blood pressure reductions of 17 mmHg systolic/19 mmHg diastolic during their experimental sessions. Nine subjects taking hypotensive medication, who were taught progressive relaxation and hypnosis in eight to nine sessions over four to five days, experienced BP reductions of 16 mmHg systolic/14 mmHg diastolic during their experimental sessions. A control group of six subjects showed no significant blood pressure changes.
Benson and Wallace (1972a) Twenty-two hypertensives with no meditation experience were given the standard TM training. Their mean blood pressure before meditation was 150/94 mmHg. After four to sixty-three weeks of meditation practice their mean blood pressure was reduced to 141/87 mmHg.
Datey et al. (1969) Forty-seven hypertension patients practiced "Shavasana", a yogic breathing concentration and muscle relaxation technique, thirty minutes daily for approximately thirty weeks. Of these forty-seven subjects, ten who did not use antihypertensive drugs had an average systolic blood pressure reduction from 134 to 107 mmHg. A second group of twenty-two subjects, with BP well controlled by antihypertensive drugs, had an average systolic blood pressure reduction from 102 to 100 mmHg. A third group of fifteen subjects, with inadequately controlled blood pressure using antihypertensive drugs, had an average systolic blood pressure reduction from 120 to 110 mmHg. The subjects' average drug requirement was reduced to 32% of the original dosages for the second group. In group three, six patients reduced their drug requirement to 29% of the original, seven patients' dosages were unchanged, and two patients required an increased dosage.
Blood pressure is one of the easiest physiological variables to measure. The evidence just presented shows that many patients with moderate hypertension improve with meditation. Because these studies involved different types of meditation, different levels of meditation experience among subjects, and different kinds of measurement, the mechanisms mediating the improvement are uncertain. Most studies indicate that benefits disappear without continued practice [see Frankel (1976) and Patel (1976)]. Nevertheless, a therapeutic approach to hypertension involving meditation has been shown to be effective [see Patel (1977, 1984)] .
Other studies examining the effect of various forms of meditation on blood pressure include: Sothers and Anchor (1989), Kuchera (1987), Mills (1987), Caudill et al. (1987), Benson (1986), Juhl and Strandgaard (1985), Patel et al. (1985), Friskey (1985), Caudill et al. (1984a, 1984b), Muskatel et al. (1984), Benson and Caudill (1984), Lang (1984), Slaughter (1984), English (1981), Bynum (1980), and Benson et al. (1974c, 1974d).
Other Cardiovascular Changes
Evidence that meditation helps relieve certain forms of cardiovascular disease generally conforms to assertions that yoga, tai chi, and other transformational disciplines promote health. Similarly, evidence that meditators recover more quickly from stressful impacts and demonstrate fewer chronic or inappropriate emergency responses than nonmeditators agrees in a general way with teachings about the alert calm and peace of yogic practice or the effortless but appropriate behavior of Zen Buddhist and Taoist adepts.
For contemporary evidence that meditation assists individuals with forms of cardiovascular disease such as hypercholesterolemia and angina pectoris, see Barr and Benson (1984), Benson (1983c), Benson and Goodale (1981), Cooper and Aygen (1979), Zamarra et al. (1977), Benson (1976), Benson et al. (1976), Benson and Wallace (1972a), and Tulpule (1971).
Goleman and Schwartz (1976) exposed thirty experienced meditators to a stressor film, and measured responses by skin conductance, heart rate, self-report, and personality scales. The heart rates of both experienced and inexperienced meditators recovered from stressor impacts more quickly than those of control subjects, demonstrating a psychophysiological configuration in stress situations opposite to that seen in stress-related syndromes. In a study by Glueck and Stroebel (1975), meditators demonstrated fewer chronic or inappropriate activations of the emergency response.