21. Yawning Can Damage Your Lungs
Yawning is a very beneficial behavior. It has social benefits, as well as physiological ones. However, if you yawn too widely, you can hurt yourself, as one unfortunate individual found when he tore a hole in his lung.
The man was a Mr. Ou from the Wuhan province of China, who experienced a sharp pain in his chest when he yawned and stretched one morning. Doctors at the hospital found he had something called spontaneous pneumothorax, a condition that develops when a pocket of air becomes trapped inside the chest.