Slow breathing during Zazen may increase cardiac variability oscillation amplitude through resonance and vagal modulation inhibition.
These data are consistent with the theory that increased oscillation amplitude during slow breathing is caused by resonance between cardiac variability caused by respiration and that produced by physiological processes underlying slower rhythms. The rhythm irregularities during inhalation may be related to inhibition of vagal modulation during the cardioacceleratory phase. It is not known whether they reflect cardiopathology.
Lehrer et al. (Mon,) studied this question.