Sudden lumbar pain like a flash may be caused by acute lumbar sprain, lumbar disc herniation, lumbar muscle strain, lumbar vertebrae instability and other reasons. 1. Acute lumbar sprain: mostly due to the sudden rotation of the lumbar muscles strained, lumbar pain and activity restrictions. 2. Herniated lumbar intervertebral disc: one of the most common causes of lumbar spinal disc, due to the rupture of the annulus fibrosus, the nucleus pulposus protrudes, resulting in compression of the local nerve roots, through the conduction of abnormalities, which can lead to sudden symptoms of back pain. 3. Lumbar muscle strain: the lumbar muscles due to long-term stress, overwork, resulting in a decline in muscle function, lumbar muscle strain. Similar symptoms may appear after reaching a certain level. 3. Lumbar vertebrae instability: lumbar intervertebral structure can be gradually metamorphosed with the increase in age, the stability gradually deteriorate, resulting in a sudden appearance of lumbar pain during normal activities. What is the cause of this problem? You need to consult a doctor in time for examination and treatment under the guidance of a doctor.