 Randomized clinical trial to evaluate the elongation of the hamstrings after making different types of stretching and mobilizations used in physiotherapy. This study is realized with university students to be long time studying in sitting position, and each subject is randomly assigned to one of three different groups. One group receives 10 minutes of global postural reeducation stretching RPG, another group receives 10 minutes of bilateral mobilization of sciatic nerve, and a third group received a placebo treatment. The evaluation of these treatments are done previously, immediately after and 20 min later. The test used to evaluate elongation are the Sit and Reach and active knee extension AKE test. The order of measurement of each test is also randomized in each subject. The intervention is always applied to the same physical therapist, and measurements were always performed by another physiotherapist blinded. 