The optimal length of sleep for a nap is about 15-30 minutes. Napping not only helps to relieve the tension and irritability of the morning work, but also makes up for the effects caused by sleepless nights or waking up too early to improve the efficiency of the afternoon. It is usually recommended to take a nap about 30 minutes after lunch, and sleep for about 15-30 minutes is appropriate. Because naps usually belong to shallow sleep, when the brain blood vessels are in a state of expansion, if the nap time is too long, may lead to insufficient blood supply to the brain, resulting in brain ischemia, lack of oxygen, after waking up may appear dizziness, headache, more sleepy and other symptoms. Nap can be chosen in a quiet, light place, if not convenient side nap, you can wear a U-shaped pillow in the neck, sleep against the back of the chair, not only to reduce the squeeze, but also to let the cervical spine and other parts of the relaxation and recuperation, more help to sleep.