When you hold your breath your heart rate slows for a few reasons. The first reason is that the autonomic nervous system which controls your involuntary functions like heart rate and digestion slows down. The second reason is that holding your breath decreases the amount of carbon dioxide in your blood. Carbon dioxide is a gas that helps regulate your blood pressure and heart rate. When the levels of carbon dioxide in your blood drop your blood vessels constrict and your heart rate slows.
Why does heart rate decrease when holding breath?
The act of holding one’s breath lowers the heart rate by stimulating the vagus nerve.
This nerve regulates the body’s involuntary functions including heart rate.
Stimulation of the vagus nerve slows the heart rate.
