In a letter to the American Heart Journal, Kothari et al. (1973) described a remarkable feat in which an ECG was attached to a yogi before he entered an eight day meditative trance. Remarkably, on the second day of the yogi’s trance, the ECG recorded minimal heart activity indicating that the meditative trance had slowed the yogi’s heart dramatically. The authors of the study ruled out mechanical disturbance or failure, and concluded that a likely cause was that the meditative trance allowed the yogi great control of his heart rate, however conceded that feat could have been a cleverly disguised trick.
The study can be found here.
Tristan Boyd, Dr Ramesh Manocha.