Tightness in the calf muscles when sitting for a long time may be caused by lumbar disc herniation. Patients with lumbar disc herniation, the protruding disc may compress the sciatic nerve, thus causing sciatica, patients in addition to the symptoms of lumbar pain, there may be symptoms of calf muscle pain. In addition to the symptoms of low back pain, patients may also suffer from calf muscle pain. In addition, the tightness of calf muscles when sitting for a long time may also be caused by long time sitting and standing, causing poor venous return, which is easy to cause the symptoms of muscle tightness. In particular, patients suffering from varicose veins or phlebitis of the lower extremities, thrombosis of the lower extremity veins in the prolonged sitting and standing, may cause the lower extremity venous reflux aggravation, so that the lower extremity soreness and discomfort, muscle tightness. When sitting or standing for a long time, you should pay attention to get up and move around, and you can do proper massage and acupressure on your legs, which can help promote blood circulation of the muscles and alleviate the symptoms of muscle tightness. If accompanied by other symptoms, also need to go to the hospital for further examination to clarify the diagnosis, and according to the cause of targeted treatment.