I found an interesting web site reviewing lots of the scientific resrearch done on meditation, from the 50's up to now. I'm pasting an excerpt that's particularly interesting for freedivers.
Here's the link.
29. Satyanarayanamurthi and Shastry, 1958. Anand and Chhina, again, investigated three yogis who said they could stop their hearts. They found that to accomplish this, all three increased their intrathoracic pressure by forceful abdominal contractions with closed glottis after inspiration or expiration. Like Bagchi and Wenger, they discovered that their subjects' heartbeats could not be detected with a stethoscope after such a maneuver and that their arterial pulse could not be felt, though EKGs showed that their hearts were contracting normally with a deviation of axis to the right when the subjects held their breath after inspiration, and a deviation to the left after expiration. Furthermore, X-ray examinations showed that each subject's heart became narrower in transverse diameter and somewhat tubular while he was trying to stop it. The three yogis "could not stop . . . their heart beats," Anand and Chhina wrote, "[but] they greatly decreased their cardiac output by decreasing venous return [and] the decrease in cardiac output is responsible for the imperceptible arterial pulse. This practice of yogis is identical with the Valsalva maneuver." Like Bagchi and Wenger, they suggested that Brosse's experiment had been flawed because she had used a single EKG lead with her subject.
30. Anand et al., 1961. A second study with an airtight box reported by P. V. Karambelkar and associates compared the reactions of an accomplished yogi, a yoga student, and two controls during confinements ranging from 12 to 18 hours. The box used in this experiment was closely monitored for oxygen and carbon dioxide content, having been thoroughly tested for leakage, and the subjects were attached to an EKG, a respiratory strain gauge belt, an EEG, a blood pressure recording device, and a measure of their galvanic skin response. Each subject stayed in the box until its CO2 level caused him discomfort. The yogi remained for 18 hours, until the air he was breathing reached 7.7% CO2, while the other three stayed from 12 1/2 to 13 3/4 hours, when their CO2 levels reached 6.6 to 7.2%. The yogi stayed longer, the authors suggested, because he was habituated to such situations. But their yoga student, not their professional yogi, showed the least reduction in oxygen consumption as his CO2 levels increased. He could withstand higher levels of CO2, the authors argued, because for three years he had practiced the kumbhaka or breath-holding exercise of pranayama, which had trained his body to function with the increased alveolar CO2 the exercise produces. Subsequently, the professional yogi increased his pranayama practice and exhibited improved adaptation to CO2 (Karambelkar, Vinekar and Bhole, 1968; and Bhole, et al., 1967).
These are actually references from the main article: -(tenth paragraph down).
Adrian
Here's the link.
29. Satyanarayanamurthi and Shastry, 1958. Anand and Chhina, again, investigated three yogis who said they could stop their hearts. They found that to accomplish this, all three increased their intrathoracic pressure by forceful abdominal contractions with closed glottis after inspiration or expiration. Like Bagchi and Wenger, they discovered that their subjects' heartbeats could not be detected with a stethoscope after such a maneuver and that their arterial pulse could not be felt, though EKGs showed that their hearts were contracting normally with a deviation of axis to the right when the subjects held their breath after inspiration, and a deviation to the left after expiration. Furthermore, X-ray examinations showed that each subject's heart became narrower in transverse diameter and somewhat tubular while he was trying to stop it. The three yogis "could not stop . . . their heart beats," Anand and Chhina wrote, "[but] they greatly decreased their cardiac output by decreasing venous return [and] the decrease in cardiac output is responsible for the imperceptible arterial pulse. This practice of yogis is identical with the Valsalva maneuver." Like Bagchi and Wenger, they suggested that Brosse's experiment had been flawed because she had used a single EKG lead with her subject.
30. Anand et al., 1961. A second study with an airtight box reported by P. V. Karambelkar and associates compared the reactions of an accomplished yogi, a yoga student, and two controls during confinements ranging from 12 to 18 hours. The box used in this experiment was closely monitored for oxygen and carbon dioxide content, having been thoroughly tested for leakage, and the subjects were attached to an EKG, a respiratory strain gauge belt, an EEG, a blood pressure recording device, and a measure of their galvanic skin response. Each subject stayed in the box until its CO2 level caused him discomfort. The yogi remained for 18 hours, until the air he was breathing reached 7.7% CO2, while the other three stayed from 12 1/2 to 13 3/4 hours, when their CO2 levels reached 6.6 to 7.2%. The yogi stayed longer, the authors suggested, because he was habituated to such situations. But their yoga student, not their professional yogi, showed the least reduction in oxygen consumption as his CO2 levels increased. He could withstand higher levels of CO2, the authors argued, because for three years he had practiced the kumbhaka or breath-holding exercise of pranayama, which had trained his body to function with the increased alveolar CO2 the exercise produces. Subsequently, the professional yogi increased his pranayama practice and exhibited improved adaptation to CO2 (Karambelkar, Vinekar and Bhole, 1968; and Bhole, et al., 1967).
These are actually references from the main article: -(tenth paragraph down).
Adrian
