Heart rate variability associated with experienced Zen meditation

To understand the control of hemodynamic events elicited by deep Zen meditation during Zazen, we studied heart rate in 5 experienced Zen meditators and 5 beginners. The study took place over 4 sets of Zen meditations in a quiet, Zen practice hall in Kamakura or Tokyo. Each set of Zazen lasted for 25 minutes which was preceded by specific respiratory exercise. The first sets were used for habituation, and the ECG data obtained from the following three sets were used for analysis. Power spectrum analysis showed distinctive change in frequency components. Low and high frequency components increased for experienced meditators. Most notably, detrended fluctuations analysis (DFA) of HRV were around 1/2 for experienced meditators and 0.78 for beginners. We attribute the decrease of DFA exponent in experienced meditators to the effective regulation of mind during meditation toward the edge of sleep, but not quite over it.