Gabe Mirkin, M.D.
During yawning, you breathe in deeply while you hold
your facial muscles tightly contracted. Normally, you breathe 15
to 20 times a minute. When you feel tired, you may breathe only
half as often, and may not get as much oxygen as you need,
which causes nerve cells in your brainstem to make you breathe
deeper and faster, and your facial muscles to contract in a yawn.
Breathing deeper and faster brings in more oxygen which
refreshes you for a few seconds, but it also causes you to blow
off more carbon dioxide from your bloodstream, which can make
you feel dizzy and more tired. So yawing also can help put you
to sleep, which is the most effective treatment for tiredness.
After you nap, you can wake up feeling refreshed.
December 10, 2005