Can breathing affect heart rate?

Yes, breathing can significantly affect heart rate. This effect is due to the mechanism called respiratory sinus arrhythmia. When you inhale, particularly if you do so vigorously or extend the duration of the inhalation, your heart rate increases. This occurs because the diaphragm moves downward, expanding the space in the thoracic cavity and temporarily increasing the volume of the heart. As a result, the blood moves more slowly through this increased space, prompting the autonomic nervous system to send signals that accelerate the heart rate.

Conversely, when you exhale, particularly if the exhale is extended or vigorous, your heart rate decreases. This happens because the diaphragm moves upward, decreasing the space in the thoracic cavity and reducing the heart's volume. The blood then moves more speedily through this smaller volume, and the nervous system sends signals to slow the heart rate down. This interaction between breathing and heart rate plays a crucial role in practices that involve controlling breath to modulate heart rate, such as in various relaxation and meditation techniques 1 2.