The motor segments of the lumbar spine, the functional units of the lumbar spine, are the two adjacent vertebrae and the soft tissues between them. The stability of the normal lumbar spine is maintained by the intervertebral discs, small intervertebral joints and ligaments, and is influenced by the surrounding nerves, muscles, abdominal pressure and other factors. 1, in the process of lumbar spine movement, the intervertebral range of motion depends on the intervertebral disc, and the direction of activity depends on the intervertebral small joints: small joints close to the sagittal position, the vertebral body is prone to anterior displacement; and the proximity to the horizontal plane will increase the range of dorsal extension rotation. The elastic strength of the intervertebral discs, especially the annulus fibrosus, is an important factor governing the abnormal activity between the vertebral endplates. In the case of a compressive load on the vertebral body, the annulus fibrosus will be subjected to a 4-5 times greater draft load. The ligaments help prevent flexion rotation or anterior displacement, the ligamentum flavum applies prestress to the intervertebral disc in neutral position and can assist in the intrinsic support of the spine, while the small joints play an important role in preventing posterior extension rotation and anterior displacement. 2, flexion-extension shear and torsional rotation loads produce greater stresses on the disc than those produced by axial extrusion, and are prone to small joint degeneration and hyperplasia. Paravertebral muscles play an important role in preventing compression of the vertebral body at maximum extension, which can lead to the occurrence of “self-injury” in the lumbar spine when degeneration, injury and strain. 3, the segmental motion of the lumbar spine contains six different degrees of free movement, and its range of motion is a common expression of the amount of activity. The lumbar segment has greater lateral bending activity and the lumbosacral segment has more rotational movement due to the guidance of the posterior part of the motion segment. The first 50-60° of flexion motion occurs in the lumbar spine, and thereafter it is mainly anterior tilt of the pelvis. The functional movement of the lumbar spine refers to the combination of different motion segments of the lumbar spine and the synergistic effect of the lumbar spine and the pelvis The normal line of gravity of the human body is located in front of the L4 vertebra, therefore, the movement of the segments of the lumbar spine and the change of the pelvic tilt will lead to changes in the load of the lumbar spine: if the vertebral load in the upright position is set at 100, it is 50 when lying down, 150 when sitting straight, 180 when relaxed, and in the state of hip flexion and traction, the lumbar spine In the state of hip flexion and traction, the load on the lumbar spine is minimal, while walking, lifting heavy objects and functional exercise will increase. Understanding the changes in the load on the lumbar spine in different functional states will help us to avoid harm and protect the functional structure of the lumbar spine as much as possible in clinical work and life.