Abstract: “Background: Flexibility is an important physical fitness marker playing a vital role in maintaining normal biomechanical function in sports and activities of daily life. Inadequate flexibility is a causative factor that may lead to muscle injury, particularly if the hamstring group of muscles is involved. Objective: To compare the effectiveness of Post-isometric relaxation (PIR) and Static Stretching (SS) on hamstring flexibility among young children. Materials and Methods: One hundred and twenty 9 to 11 years old children identified as having hamstrings tightness assessed by passive straight leg raise test were recruited and allocated into three groups: post-isometric relaxation, static stretching and control group. Both intervention groups performed stretching and the control group was not involved in any stretching programme. The exercises were performed for 5 days in a week for six weeks. Passive straight leg raise test was used to assess hamstring flexibility and the measurement w”

Keywords: Hamstring flexibility, Hamstring tightness, children, post isometric relaxation, static stretching