Thigh pain when exerting oneself in stool is considered to be caused by physiological factors such as improper posture for a long time, or it may be caused by pathologic factors such as lumbar disc herniation and pyriformis syndrome. 1. Physiological factors: due to prolonged improper posture, compression of peripheral nerves and muscles, can lead to transient local blood circulation is not good, causing thigh pain or numbness, is a normal physiological phenomenon, to change the posture, to lift the local compression, can be relieved. 2. Herniated lumbar disc: Herniated lumbar disc can cause the nucleus pulposus to protrude and irritate or compress the nerve root. When the sciatic nerve is compressed, the pain can be radiated from the buttocks along the back of the thighs to the calves and the feet, and when bending down and exerting oneself in bowel movements, the nerve compression will be aggravated, and the pain in thighs will appear. 3. Piriformis syndrome: Piriformis syndrome is mostly due to trauma and other factors caused by the hypertrophy of the piriformis muscle, compression of the sciatic nerve pain, when bending over and bowel movements, the nerve compression symptoms will be more pronounced, so there is a thigh pain or aggravation of the pain phenomenon. There may be other reasons for thigh pain when straining to defecate, so it is recommended that patients go to the hospital in time for examination and standardized treatment to clarify the cause of the disease.