Bending over for a while may not straighten up for the following reasons: First, it may be cold or wind chill leading to poor blood flow in the back of the waist, the back of the waist muscle stiffness so that it can not straighten up. Second, may be overwork caused by lumbar muscle strain, lumbar muscles continue to tension, can not relax and form muscle spasm. Three, may also be caused by lumbar disc herniation, lumbar disc herniation will cause pressure changes in the spinal canal, through the sinus nerve reflexes and cause lumbar pain symptoms, sometimes accompanied by radioactive pain and numbness in the lower limbs. The pressure in the spinal canal will increase when you bend down, so the pain will intensify, so you can’t straighten up, and its relatively serious. It is recommended to pay more attention to rest, try to sleep on a hard bed, do not do strenuous exercise, do not sit for a long time, and do not catch a cold. If you don’t get relief after some time, it is recommended to go to the hospital for examination.