The main factors affecting the skeletal muscle contraction are as follows: 1. the intracranial lesions, such as cerebral hemorrhage, brain tumor, or cerebral infarction, may cause extrusion and stimulation of the surrounding cerebral nerves, resulting in the inability of the nerves to innervate the skeletal muscles, and therefore the inability of the skeletal muscles to contract. 2. the nerve roots, such as the nerve roots in the cervical and lumbar spine, may cause extrusion and stimulation, disc herniation or 3. Injuries to peripheral nerves, such as the sciatic nerve, femoral nerve, radial nerve, median nerve, ulnar nerve, etc., may decrease the innervation of skeletal muscles and affect the contraction of skeletal muscles. 4. 4. The contraction of skeletal muscles is affected by injuries or strains to the surrounding tendons, ligaments, muscles and other structures, which can cause severe pain when contracting the skeletal muscles.