Back pain from bending may be caused by strenuous back activities or by certain diseases such as lumbar muscle strain and herniated disc. 1. Strenuous back activities: back muscles after strenuous activities resulting in lactic acid accumulation, back pain may occur, in bending and other actions that involve the back muscles, the symptoms worsen. 2. Lumbar muscle strain: long-term bending work, engaged in heavy physical workers may have lumbar back muscle strain, the phenomenon of back pain after bending. 3. Herniated disc: After a herniated disc in the lumbar back, the nucleus pulposus protrudes and compresses the nerves causing pain in the lumbar back, which is aggravated when bending. There are many other diseases that cause back pain after bending over, such as supraspinal ligamentitis, back fasciitis, tumor compression, etc. It is recommended to go to the regular hospital in time, and under the guidance of the doctor to clarify the cause of the disease and actively treat it.