yawn

A yawn takes about 6 seconds. During this period, people's eyes are closed and their nerves and muscles are completely relaxed. Therefore, it can be considered that yawning gives people the best rest physically and psychologically, and has an important physiological protective effect on the human body. Some people think that yawning is a manifestation of hypoxia in the brain. Through deep breathing exercises of yawning, the human body increases oxygen in the blood and emits more carbon dioxide, thereby making people more energetic. When people are sleepy, they often yawn continuously to remind the human body that the brain is tired and needs to rest, so yawning is also a method of hypnosis. When people are about to enter a stressful job, they often yawn again and again. This may be because the human body uses deep inhalation to increase more oxygen in the blood and improve the brain's ability to move.