Use a chair as a helpful tool in stretching the backs of your upper thighs, or hamstrings. The elevation of the chair allows you to maintain a straight back so you can focus the stretch in the legs.
Stand in front of a sturdy chair with toes facing forward. Shift your weight to your left leg and place your right foot on the seat of the chair, keeping your right knee straight and your toes facing up toward the ceiling. Maintain a straight back as you bend forward at the hips, resting your fingertips on the chair seat on each side of your foot. Pause for three to six breaths, feeling the stretch in the back of your right thigh. Repeat on the other side.
As your legs become more flexible, practice a more advanced version of the stretch — placing your right foot on the top of the chair backrest and resting your hands on the top of the chair on each side of the foot. As before, pause for three to six breaths, feeling the stretch in the back of your right thigh. Repeat on the other side.
Source : Los Angeles Times