STARTING POSITION:
Lie on your back on a mat and rest your head on it. Place a foam roller between the top of your butt and the floor. Grab your right knee and extend your left knee.
MOVEMENT:
Slowly pull your knee towards the chest and relax the left leg until you feel the stretch in your hip flexors. Maintain the stretch during the required time and then do it with the other side.
TIPS: You should feel the stretch of the muscles but not pain.