The Efficacy of Focus Extracorporeal Shock Wave Therapy on Hamstring Tightness

Inclusion Criteria: * Limited hamstring flexibility; passive knee extension degree \>20 * No underlying disease Exclusion Criteria: * Patients with history of physical therapy in past 3 month * Patient with analgesic drug such as muscle relaxant or NSAID. * Patient with limited hamstring flexibility due to neurological or musculoskeletal diseases. * Patient with cardiac pacemaker, pregnancy, hypercoagulable conditions, severe osteoporosis, malignancy or active infection around intervention site. * Patient with history of chronic knee or back pain * Patient cannot follow home stretching exercise program