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The Physiology of Meditation

Dr. Swami Karmananda Saraswati; MB, BS (syd) 
Psychologists and medical workers throughout the world have conducted an impressive number of investigations into the alterations of physiological, endocrine and metabolic functions which accompany meditative states of consciousness. Meditation has been found to bring about relaxation and balance in cardiac, respiratory, hormonal and circulatory systems, and is being recommended by many doctors for patients suffering from diverse psychosomatic and stress induced illnesses. In addition, large numbers of men and women are integrating simple meditation as an effective preventive and relaxative therapy into their highly stressed and competitive modern lifestyles. At the same time, psychologists and psychiatrists have reported profound alterations in mental health and emotional well being, together with diminished subjective and objective manifestations of anxiety, in individuals who practise meditation for a short period each day. Laboratory studies have already confirmed the following physiological effects of the practice of japa (mantra meditation):
  1. Decreased minute respiratory volume.
  2. Decreased oxygen consumption.
  3. Decreased carbon dioxide elimination.
    (These observations reflect a diminished oxygen requirement by the tissues of the body during meditation.)
  4. No change in blood pressure.
  5. Decreased arterial blood lactate (*1) indicating a high level of muscular relaxation.
  6. Increased central and frontal slow wave EEG activity.
  7. Distinctively increased coherence in EEG recordings from different regions of the scalp (*1, 2) indicating synchronisation of the brain waves.
  8. Decreased adrenocortical activity (*3) of the body's stress coping mechanisms.
In a recent study, researchers at the University of California Medical School have investigated the changes in regional distribution of blood flow in the body during japa meditation. (*3)

They measured the total cardiac output (CO), and the alteration in blood flow (BF), to those organs which receive the highest percentage of the total cardiac output, i.e. the liver (hepatic BF) and kidneys (renal BF). For their experiment 27 normal young university students were divided into two groups. The first group of 6 males and 8 females had been practising meditation twice a day for over one year, while the second control group, consisting of 6 male and 7 female volunteers without meditative experience, were observed while they were engaged in simple relaxation with their eyes closed.

The study utilised clearance methods for determining hepatic and renal blood flow, dye dilution techniques to determine cardiac output, volumetric impedance pneumography to indirectly measure minute volume, and enzymatic measurements of plasma lactate. Measurements were taken before, during and after meditation or relaxation.

Results: 
  • Decreased renal blood flow in both groups, meditators by 29% and non-meditators by 32%.
  • Decrease of 34% in hepatic blood flow, observed only in the meditator group.
  • Increase of 16% in cardiac output observed in the meditator group.
  • Decreased minute volume in the meditators.
  • Decreased plasma lactate in the meditators.
  • No change in heart rate.
Conclusion:
Eyes closed relaxation is associated with a marked decline of renal blood flow, but little change in hepatic flow, with cardiac output unchanged.

The hypometabolic meditative state is associated with a persisting decrease in hepatic blood flow, a decreased renal blood flow and an increased cardiac output. These figures imply an increase of 44% in non-renal and non-hepatic components of blood flow, suggesting a marked increase in the blood supply to the skin and the brain during meditation.

These increases, coupled with decreased plasma Cortisol and lactate levels persisting well after completion of meditation, may partly explain the subjective reports of meditators that they felt more relaxed, alert and aware of themselves, their lives and their environment after adopting meditation on a regular basis.

References:
*1. Wallace, R.K., Benson, H., and Wilson, A.F.: 'A wakeful hypometabolic state', Amer. J. Physiol., 221, pp. 795-799, 1971.
*2. Banquet, J.P.: 'Spectral analysis of EEG during transcendental meditation', Electroencephal. Clin. Neurophysiol., 35, pp. 142-149, 1973.
*3. Jevning, R., Wilson, A.F., Smith, W.R. and Morton, M.E.: 'Redistribution of blood flow in acute hypometabolic behavior', Amer. J. Physiol., 235(1), pp. R89-R92, 1978.

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