Objectives: The objectives of the study were to find the effective techniques out of post isometric relaxation, Maximum voluntary isometric contraction and PNF hold relax in increasing the flexibility of hamstring muscles. Materials and Methods: An observational study on 90 subjects (both sexes; between 18 and 30 years) was given one of three interventions – PIR, 10 Sec MVIC, and PNF HR and assigned into three groups – Group A, B, and C (each group with 30 subjects). Three repetitions of the protocol were given to each subject for regular 2 days. Active knee extension ROM was measured by the AKE test (90–90 test) before and after the treatment session both days. The data were collected, and percentage analysis was used to interpret the results. Results: All the groups showed a significant increase in active knee extension ROM. However, the results were more significant for Group B than Group A than Group C with mean differences 5.53, 4.97, and 3.83, respectively. Conclusion: Hence, it is concluded that 10 s, MVIC was the most effective among the three manual techniques.