Prof. J.P.N. Mishra
Mental states can markedly alter physiologic function. For example, stressful situations result in a hyper metabolic state, with increased oxygen consumption, heart rate, and blood pressure. In contrast, the majority of scientific studies show meditation to be a wakeful state accompanied by a decreased metabolism. This generalized decrease in body metabolism manifests with a decreased breathing pattern, decreased heart rate, and decreased blood pressure. There is also a marked decrease in the level of oxygen utilization and carbon dioxide elimination by muscle. These findings have been verified by an impressive number of studies.
Oxygen consumption is generally regarded as a reliable index of physical activity and arousal. For example, exercise requires an increased consumption of oxygen by muscle. During this metabolic process, oxygen is converted to carbon dioxide, which is eliminated by the lungs. If the body is starved of oxygen, reduced oxygen consumption does not lead to a parallel reduction in carbon dioxide elimination because the cells continue to metabolize the remaining oxygen in the blood. Therefore, oxygen starvation causes a decrease in the concentration of oxygen and an increase in the concentration of carbon dioxide in arterial blood. The relative amount of oxygen and carbon dioxide in the blood is called the respiratory quotient. During normal respiratory processes, this quotient remains constant; in abnormal respiratory situations, however, the reduction in available oxygen and increase in carbon dioxide changes the quotient. Wallace et al (1971) found that during the practice of meditation the amount of carbon dioxide elimination drops in proportion to the amount of oxygen consumed; therefore, the respiratory quotient remains constant. In conclusion, the metabolic changes of meditation arise from a natural reduction in metabolic activity at the cellular level, not from a forced reduction of breathing.
Circulation, especially in muscle and brain, is closely related to the metabolic requirements of tissues, and is very sensitive and consistent in its response to behavior. A study by Jevning et al (1996) illustrates an interesting redistribution in the blood flow of meditators. Blood flow to the kidneys and liver declined in practitioners, with a surprising increase in cardiac output. These changes of blood flow imply a marked redistribution of blood flow during meditation. It is hypothesized that most of the distributed circulation must be to the brain, a hypothesis that has been supported by direct estimation of increased relative cerebral blood flow (Herzog et al 1990, Jevning et al 1992, Jevning et al 1996). The redistribution of blood flow with an increase in cardiac output has interesting significance for the pattern of metabolic changes elicited by meditation; although the response to meditation is hypo metabolic overall, it appears likely that there is a concomitant increase in the metabolism of certain tissues.
