There are many reasons for back pain from lifting heavy objects, which may be due to strained lumbar muscles or ligaments, lumbar muscle strain, herniated lumbar discs, ureteral stones, and so on. You should consult a doctor to find out the cause. 1. Lumbar muscle or ligament strain: Due to weak lumbar muscles or overloading of the lumbar muscles by heavy loads, strains of the lumbar muscles or ligaments may occur, causing pain in the lumbar region. 2. Lumbar muscle strain: prolonged and repeated excessive lumbar movement and overloading, such as sitting, standing or repeatedly bending over with heavy objects, so that the lumbar muscles are in a state of tension for a long period of time, which may lead to lumbar muscle strain, and symptoms of lumbar pain occur when lifting heavy objects. 3. Herniated lumbar disc: lifting heavy objects may aggravate the herniated lumbar disc, the nucleus pulposus breaks through the annulus fibrosus, resulting in compression of peripheral nerves and tissues, which leads to low back pain. 4. Ureteral stones: lifting heavy objects may cause ureteral stones to become embedded, causing back pain. Hydrocele, cysts and other diseases can also cause back pain, back pain symptoms should be timely medical care, identify the causes, under the guidance of the doctor treatment, do not take measures on their own.