There are physiological factors for calf weakness and tenderness, and pathological factors such as lumbar disc herniation, lumbar spinal stenosis, hypokalemia, pyriformis syndrome and myasthenia gravis. 1. Physiological factors: for example, muscle strain caused by standing for a long time or walking too much, which can be reduced by rest. 2. Lumbar intervertebral disc herniation: Herniated intervertebral disc compressing the nerves can cause calf weakness and numbness. 3. Lumbar spinal stenosis: it can cause weakness of lower limbs and intermittent claudication. 4. Hypokalemia: excessive loss or insufficient intake of potassium may cause lower limb weakness, which is gradually aggravated. 5. Piriformis syndrome: Piriformis muscle compresses the sciatic nerve, resulting in calf weakness and limitation of joint movement. 6. Myasthenia gravis: belonging to the nervous system diseases, calf weakness gradually aggravated, muscle atrophy. If the calf weakness is not improved by resting, it is recommended to go to the hospital in time to check the cause of the disease and then treatment.