1) When lying on the left side, the legs are slightly bent, which is beneficial to the relaxation of the body and the elimination of fatigue. But as we all know, the heart is located on the left side in the chest cavity, and the exits from duodenum and small intestine to large intestine are on the left side, so lying on the left side will squeeze the heart, affect the gastrointestinal tract and slow down the gastric emptying.

2) When lying on the right side, your legs are slightly bent. At this time, the heart is in a high position and will not be oppressed, and the liver is in a low position, and the blood supply is good, which is very beneficial to metabolism. There is still a little food in the stomach that will push to the duodenum, which can promote digestion and absorption. At this time, the whole body is in a relaxed state, breathing evenly, the heartbeat slows down, and the brain, heart, lungs, gastrointestinal tract, muscles, etc. Will get enough rest and oxygen supply.

3) Lying on your back is the most common sleeping position. In this sleeping position, the body and lower limbs are just fixed in a straight position, which can not achieve the purpose of full body rest. When the pressure in the abdominal cavity increases, lying on your back can easily make people feel chest tightness and panic. Some people will unconsciously put their hands on their chests when lying on their backs, which will put pressure on the heart and lungs and make them prone to nightmares.