 Randomized clinical trial to evaluate the elongation of the hamstrings after making different types of stretching. One group receives a stretch of global postural reeducation RPG, another group receives a 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. 