It is no coincidence that most of the world’s spiritual and contemplative disciplines involve some form of breathing focused practice.

This paper provides a comprehensive review of the scientific literature concerning the beneficial effects of slow breathing on our physiological systems.

Including:

• Enhances ventilation efficiency and arterial oxygenation via alveolar recruitment, and distension and reduction of alveolar dead space.
• Increases venous return → increases filling of the right heart → increases stroke volume → increases cardiac output.
• Causes blood pressure pulse fluctuations to synchronise with heart beat rhythm
• May decrease mean blood pressure
• Synchronisation of pulse harmonics of blood flow and heart rhythm
• Increases vagal activity (vagal tone).
• Improves autonomic responsiveness to physical perturbations (eg getting dizzy when you suddenly stand up)

Here is my post on breathing to give you a quick idea what a regular practice of slow breathing looks like.

According to the studies reviewed here, “autonomically optimised respiration” would appear to be in the band of 6–10 breaths per min, with an increased tidal volume that is achieved by diaphragmatic activation. Although not reviewed here, nasal breathing is also considered an important component of optimised respiration. This is easily achievable in most individuals with simple practise and there is yet to appear in the literature any documented adverse effects of respiration in the 6–10 breaths per min range. Controlled, slow breathing appears to be an effective means of maximising HRV and preserving autonomic function, both of which have been associated with decreased mortality in pathological states and longevity in the general population

Link to full article (pdf): The physiological effects of slow breathing in the healthy human.