Doing flat support back pain may be caused by improper posture, lumbar disc herniation, lumbar muscle strain and other factors. 1. Improper posture: Improper posture when doing flat support may lead to lumbar muscle strain, which may lead to the phenomenon of flat support back pain. 2. Herniated lumbar intervertebral disc: it is usually caused by a variety of factors such as degeneration of lumbar vertebrae, trauma, and so on, which leads to rupture of the fibrous ring of the intervertebral discs under the action of external forces, and the local tissues are compressed or stimulated, thus resulting in the phenomenon of lumbar pain. 3. Lumbar muscle strain: often overwork, trauma and other factors, resulting in chronic injurious inflammation of the lumbar muscle tissue. When doing flatbed support, it will make the lumbar load-bearing force increase, and the phenomenon of pain occurs. There may be other reasons to do flat support lumbar pain, should go to the hospital in time for examination, clear causes, standardized treatment under the guidance of the doctor.