Why do hotels have four pillows? How high should they be?

The four pillows in the hotel room can play different roles according to the sleeping position. When lying on your back, if your shoulders exceed the pillow, it will easily cause pressure on the cervical spine; If only half of the head is attached to the pillow, the cervical vertebra will be suspended, which is also an inappropriate sleeping position. At this time, you can put a pillow under your head and neck to make a real pillow. The pillow should be just padded to the whole head to the neck, not to the shoulders, and not only to the half of the back of the head. The other pillow is placed under the knee, which can make the knee joint in a state of mild flexion and relaxation. If you lie on your side, the width of your shoulders will cause your head and neck to hang up. If the pillow is low, you can put two pillows together and put a small pillow between your knees, which will make you feel very comfortable. In addition, it is best to avoid sleeping, because the cervical spine will bear too much pressure; Remember to stand on your side when you get up, raise your hands, and then get out of bed. Don't just sit up straight on your back. When sleeping on a pillow with a height of 6 ~ 9 cm, the EEG first appears a smooth rest waveform, which indicates that the brain enters a stable sleep state smoothly and obtains the highest sleep quality. In other words, a pillow 6 ~ 9 cm high is a reasonable choice.