Easy to flash back for more reasons, the common ones are mainly the following: 1, the person itself is relatively thin, waist, back muscles are very underdeveloped, the force of the lumbar spine protection is very weak. 2, daily life like bending, sedentary, standing, the lumbar spine itself is also in a state of strain, strain. 3, there was no thorough, systematic treatment after a previous lumbar sprain, always have pain stimulation of the lumbar spine area. At this time, due to the self-protective reaction of the person will also be due to a long time range of activities reduced, resulting in muscle atrophy around the lumbar spine, the protection of the lumbar spine strength is weakened. 4, itself has appeared lumbar degenerative changes or lumbar disc herniation, spinal stenosis and other underlying pathologies. 5, wind, cold is also a causative factor.