The hamstrings which are located at the back of your upper leg, when contracted, bring your heel to your buttocks.   These muscles attach onto the bone in your buttock region that you feel when you sit on a hard surface and travel down the back of the leg to attach around the knee region.   As you can see in the picture to the right, the hamstrings are in a contracted state.   If this position is held for long periods of time the hamstring muscles will become shortened.  If the hamstrings are too tight, when a person tries to rise up from a sitting position, the attachment point on the bone in the buttock region will pull the pelvis into a tilt.  When this tilt occurs it alters the posture of the low back causing pain.

To stretch the hamstrings; sit on the floor, tuck one foot into your pelvis and straighten the other leg in the direction of a V.  Point the toe of the straight leg to the ceiling.  With a flat back gently lean forward and reach towards your toe.  If you cannot reach your toe do not compromise your posture, just rest your hands on the top of your leg at the level you are able to reach without rounding your back.   Hold your stretches for 30 seconds and repeat 3 times for each leg.