The most common excuses I have heard for yawning....
an involuntary reflex by the body to control the levels of carbon dioxide and oxygen in the blood.
a yawn draws more oxygen into the lungs through a deep breath.
typically this happens after periods when the oxygen level is low as we have been taking short shallow breaths... bordom or fatigue
I HAVE ALSO HEARD THAT
1. yawning like that is a symptom of asthma, which can appear at any age.
2. it's a natural response to replenish air in the lungs.
3. that it aids in the release of lactic acid that builds up in your muscle while exercising