“Vagal activity is enhanced during the postinspiratory period and inhibited during the postexpiratory period.”
When I read this unassuming sentence in the Discussion of our most recent Science 411 paper, it was actually quite eye-opening for me.
It means:
Inhalations: Sympathetic
Inhale-Holds: Parasympathetic
Exhalations: Parasympathetic
Exhale-Holds: Sympathetic (I had never actually thought about this one and just assumed it was parasympathetic.)
Putting these together, we see why deeply relaxing breaths usually focus on inhale-holds and prolonged exhalations.
Let’s look at the most common example, 4-7-8 breathing. With this breath, 4 seconds are spent in sympathetic and 15 parasympathetic.
No wonder Dr. Weil says, “This breathing exercise is a natural tranquilizer for the nervous system.”