Cold water on the face slows the heart
Submerging the face in cold water, while holding the breath, triggers the mammalian dive reflex: heart rate falls and blood shifts toward the chest.
Established2 min read
Receptors on the face, served by the trigeminal nerve, plus the apnea, start a reflex that slows the heart and constricts vessels in the limbs. Seals use the full version to stretch oxygen. Humans have a smaller, reliable copy.
The reflex is a reallocation. The brain and heart keep the blood. Babies show a vigorous form; adults keep a quieter one.
Caveats
- Heart-rate drops vary widely. Cold and apnea together do more than either alone.
- It is the wrong tool for some heart conditions.
Sources
- 1Scholander P. F.. Physiological Adaptation to Diving in Animals and Man. Harvey Lectures 57, 1962.