Exercise flash to the waist, bending or backward back pain, may be related to lumbar muscle strain, lumbar spine fracture, lumbar disc herniation and other reasons. 1. Lumbar muscle strain: it is often due to the lack of activity in place or improper exercise force, resulting in lumbar muscle sprain, bending or leaning back on the waist pain. 2. Lumbar spinous process fracture: it may be caused by the pulling of muscles and ligaments when people are exercising and performing certain actions. In this case, you can usually hear a loud noise, and there will also be pain when you bend over or lean back. 3. Lumbar disc herniation: improper exertion during exercise leads to acute herniation of the lumbar intervertebral disc, and when the nerve root is compressed, it is possible that bending or leaning back in the position of the waist will aggravate the compression of the nerve root, thus producing pain. There are other reasons for exercise flash to the waist, bending or leaning back on the pain, it is recommended that timely medical care, improve the relevant examination, clear cause of the targeted treatment as prescribed by the doctor, so as not to delay the condition.